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• Linux as a router for public networks

  - by nixnotwin

  My ISP had given me a /30 network. Later, when I wanted more public ips, I requested for a /29 network. I was told to keep using my earlier /30 network on the interface which is facing ISP, and the newly given /29 network should be used on the other interface which connects to my NAT router and servers. This is what I got from the isp: WAN IP: 179.xxx.4.128/30 CUSTOMER IP : 179.xxx.4.130 ISP GATEWAY IP:179.xxx.4.129 SUBNET : 255.255.255.252 LAN IPS: 179.xxx.139.224/29 GATEWAY IP :179.xxx.139.225 SUBNET : 255.255.255.248 I have a Ubuntu pc which has two interfaces. So I am planning to do the following: eth0 will be given 179.xxx.4.130/30 gateway 179.xxx.4.129 eth1 will be given 179.xxx.139.225/29 And I will have the following in the /etc/sysctl.conf: net.ipv4.ip_forward=1 These will be iptables rules: iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT My clients which have the ips 179.xxx.139.226/29 and 179.xxx.139.227/29 will be made to use 179.xxx.139.225/29 as gateway. Will this configuration work for me? Any comments? If it works, what iptables rules can I use to have a bit of security? P.S. Both networks are non-private and there is no NATing.

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• Trouble setting up incoming VPN in Microsoft SBS 2008 through a Cisco ASA 5505 appliance

  - by Nils

  I have replaced an aging firewall (custom setup using Linux) with a Cisco ASA 5505 appliance for our network. It's a very simple setup with around 10 workstations and a single Small Business Server 2008. Setting up incoming ports for SMTP, HTTPS, remote desktop etc. to the SBS went fine - they are working like they should. However, I have not succeeded in allowing incoming VPN connections. The clients trying to connect (running Windows 7) are stuck with the "Verifying username and password..." dialog before getting an error message 30 seconds later. We have a single external, static IP, so I cannot set up the VPN connection on another IP address. I have forwarded TCP port 1723 the same way as I did for SMTP and the others, by adding a static NAT route translating traffic from the SBS server on port 1723 to the outside interface. In addition, I set up an access rule allowing all GRE packets (src any, dst any). I have figured that I must somehow forward incoming GRE packets to the SBS server, but this is where I am stuck. I am using ADSM to configure the 5505 (not console). Any help is very much appreciated!

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• How can I monitor network traffic?

  - by WIndy Weather

  I have a home network with about 10 devices including BluRay player [netflix] and both windows and linux machines. I need to collect network traffic statistics so that if questions come up about how much traffic I'm using I have the answer independent of my ISP. I've looked at DD-WRT, but I see that even buying a new router that will be supported is a problem since I might get the wrong version of the hardware. I have a DIR-655 and a DIR-501 - neither of which is supported. I don't mind buying new hardware, but it looks like a crap-shoot to get one that will work. DD-WRT looks like a bad solution unless someone knows of a place to get a router that is guaranteed to work. Does someone know of an arduino or other SBC solution? I have plenty of NAT routers already, so I just need traffic statistics for external traffic. The network is GBit Ethernet inside and Cable / soon to be DSL outside. The DIR-655 only gives me "packets", not bytes transferred oddly enough. Thanks, ww

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• Window 7 image in vmware will allow network connection out but not http

  - by Ormis

  I am currently trying to create a set of images to deploy on my network, but I've run in to a snag. When I create my own Windows 7 image I can successfully use NAT for connecting to the network but whenever I try to access a webpage I get nothing. To be more specific, All firewalls/iptables are disabled on my host machine, my virtual machine, and my network. I can do lookups and all addresses respond correctly (i'm even using Google's DNS). On the host OS i have full connectivity. On the virtual machine I can ping any device I want and all addresses resolve correctly. Within a browser I cannot reach any page via hostname or IP. I feel almost like port 80 is being blocked but i can't find any reason this would be the case. If anyone has had this occur before, I would love some insight to the problem. I initially asked this on stackoverflow and now my eyes are now opened up to superuser. Thank you for any help you can provide.

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• pfSense routing between two routers with shared network

  - by JohnCC

  I have a network set-up using two pfSense routers arranged like this:- DMZ1 WAN1 WAN2 DMZ2 | | | | | | | | \___ PF1 PF2___/ | | | | \___TRUSTED___/ Each pfSense router has its own separate WAN connection, and a separate DMZ network attached to it. They share a common TRUSTED LAN between them. The machines on the trusted network have PF1 as their default gateway. PF1 has a static route defined to DMZ2 via PF2, and PF2 has a static route to DMZ1 via PF1. There is NAT to the WAN but internal networks (DMZ1/2 and TRUSTED) use different RFC1918 subnets. I inherited this arrangement, and all used to work fine. I made a config change to PF1 (relating to multicast), and machines on DMZ2 suddenly could not talk to TRUSTED. I rolled the change back, but the problem persisted. What I guess you'd hope would happen is that TCP packets would go DMZ2 - PF2 - TRUSTED and on return TRUSTED - PF1 - PF2 - DMZ2. That's the only way I can see it would have worked. However, PF1 drops the returning packets. I've verified this using tcpdump. I've worked around this by adding static routes to DMZ2 via PF2 to the servers on TRUSTED, but some devices on there do not support static routes so this is not ideal. Is there way to make this arrangement work decently, or is the design inherently flawed? Thanks!

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• Proxmox: VMs and different public IPs

  - by Raj

  I have a server which has two NICs and both are directly connected to internet. I have five different public IP addresses available for the VMs. The host machine (Proxmox) doesn't need to use any (it'll use a private IP and that's all) but will have internet connection. I've gone through the Proxmox documentation and I'm not able to understand the big picture to set up the right network configuration for my needs. In short, what I have is: One server (Proxmox, host machine) On that server, 5 VMs are created 5 public IP addresses available (one for each VM), let's say: 80.123.21.1, 80.123.21.2, 80.123.21.3, 80.123.21.4, 80.123.21.5 What I have now for the host is the following: auto lo iface lo inet loopback auto eth0 iface eth0 inet manual auto eth1 iface eth1 inet manual auto vmbr0 iface vmbr0 inet static address 192.168.1.101 netmask 255.255.255.0 bridge_ports eth0 bridge_stp off bridge_fd 0 auto vmbr1 iface vmbr1 inet manual It can be reached from the internal network, so that's OK. It has internet connection, which is also OK. vmbr1 is going to be used by the VMs. Each VM will have its own IP on his network interfaces configuration file. For some reason, VMs will not have internet and they won't be able to have public IP address. If I use NAT, it will work correctly, but they will not use the public allocated IP addresses for them. Am I missing something?

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• Possible for linux bridge to intercept traffic?

  - by A G

  I have a linux machine setup as a bridge between a client and a server; brctl addbr0 brctl addif br0 eth1 brctl addif br0 eth2 ifconfig eth1 0.0.0.0 ifconfig eth2 0.0.0.0 ip link set br0 up I also have an application listening on port 8080 of this machine. Is it possible to have traffic destined for port 80 to be passed to my application? I have done some research and it looks like it could be done using ebtables and iptables. Here is the rest of my setup: //set the ebtables to pass this traffic up to ip for processing; DROP on the broute table should do this ebtables -t broute -A BROUTING -p ipv4 --ip-proto tcp --ip-dport 80 -j redirect --redirect-target DROP //set iptables to forward this traffic to my app listening on port 8080 iptables -t mangle -A PREROUTING -p tcp --dport 80 -j TPROXY --on-port 8080 --tproxy-mark 1/1 iptables -t mangle -A PREROUTING -p tcp -j MARK --set-mark 1/1 //once the flows are marked, have them delivered locally via loopback interface ip rule add fwmark 1/1 table 1 ip route add local 0.0.0.0/0 dev lo table 1 //enable ip packet forwarding echo 1 > /proc/sys/net/ipv4/ip_forward However nothing is coming into my application. Am I missing anything? My understanding is that the target DROP on the broute BROUTING chain will push it up to be processed by iptables. Secondly, are there any other alternatives I should investigate? Edit: IPtables gets it at nat PREROUTING, but it looks like it drops after that; the INPUT chain (in either mangle or filter) doesn't see the packet.

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• 403 Forbiden on Apache (CentOS) Server

  - by pouya

  These are my VM setup: HOST: windows 7 ultimate 32bit GUEST: CentOs 6.3 i386 Virtualization soft: Oracle virtualBox 4.1.22 Networking: NAT -> (PORT FORWARD: HOST:8080 => GUEST:80) Shared Folder: centos all the project files goes into shared folder and for each project file a virtualhost conf file is created in /etc/httpd/conf.d/ like /etc/httpd/conf.d/$domain I wasn't able to see anything in my browser before disabling both windows firewall and iptables in centos after that if i type for example: http://www.$domain:8080/ all i see is: Forbidden You don't have permission to access / on this server. Apache/2.2.15 (CentOS) Server at www.$domain.com Port 8080 A sample Virtual Host conf file: <VirtualHost *:80> #General DocumentRoot /media/sf_centos/path/to/public_html ServerAdmin webmaster@$domain ServerName www.$domain ServerAlias $domain *.$domain #Logging ErrorLog /var/log/httpd/$domain-error.log CustomLog /var/log/httpd/$domain-access.log combined #mod rewrite RewriteEngine On RewriteLog /var/log/httpd/$domain-rewrite.log RewriteLogLevel 0 </VirtualHost> centos shared folder is availabe to guest at /media/sf_centos These are file permissons for sf_centos: drwxrwx--- root vboxsf vboxsf group includes: apache and root So these are my questions: 1- How to solve Forbidden Problem? 2- How to setup both host and guest firewalls? 3- How can i improve this developement environment to simulate production environment as much as possible specially security improvements?

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• How do I setup a proper VPN for my friends to play LAN games AND give them internet access?

  - by Gizmo

  I'm trying to setup a VPN on my local network, but everyone who connects to me DOES have access to my laptop but not to the internet or other devices on the network. How can I properly configure my VPN on windows to work correctly (giving internet + access to all devices on my network to the remote pc)? Or is there software on windows which makes creating a VPN server easier? or maybe a VMWare image linux vpn server? I can't find any of those! My requirement is that my friends don't have to install additional software, they have to be able to connect with default windows stuff. My OS is Windows 8 Standart edition (not pro or enterprise) OEM. Most of my friends have also windows 8, some windows 7. Extra info: My device is DMZ'ed (Demilitarized Zone, [disabled NAT on my device so it's accessible on the WAN]) I can access files, websites and services on other devices on my network, and all devices can access file shares, website and all other services on my device When enabling VPN everything works except the client is unable to get internet access or access to any device on my network, client has only access to my device.

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• SNMP query - operation not permitted

  - by jperovic

  I am working on API that reads a lot of data via SNMP (routes, interfaces, QoS policies, etc...). Lately, I have experienced a random error stating: Operation not permitted Now, I use SNMP4J as core library and cannot really pinpoint the source of error. Some Stackoverflow questions have suggested OS being unable to open sufficient number of file handles but increasing that parameter did not help much. The strange thing is that error occurs only when iptables is up and running. Could it be that firewall is blocking some traffic? I have tried writing JUnit test that mimicked application's logic but no errors were fired... Any help would be appreciated! Thanks! IPTABLES *nat :PREROUTING ACCEPT [2:96] :POSTROUTING ACCEPT [68:4218] :OUTPUT ACCEPT [68:4218] # route redirect za SNMP Trap i syslog -A PREROUTING -i eth0 -p udp -m udp --dport 514 -j REDIRECT --to-ports 33514 -A PREROUTING -i eth0 -p udp -m udp --dport 162 -j REDIRECT --to-ports 33162 COMMIT *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT ..... # SNMP -A INPUT -p udp -m state --state NEW -m udp --dport 161 -j ACCEPT # SNMP trap -A INPUT -p udp -m state --state NEW -m udp --dport 162 -j ACCEPT -A INPUT -p udp -m state --state NEW -m udp --dport 33162 -j ACCEPT ..... -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT

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• Join Domain from VM

  - by Adis

  I have two VMs running on VMWare Player. I use NAT adapter settings. The host machine for VMs is running on corporate network. First VM has Domain controller running and I can log in on that machine using domain credentials. I named domain wm.local When I run IP config on this machine: IP: 192.168.87.132 Def Gataway: 192.168.87.2 DNS server: 192.168.87.2 DHCP server: 192.168.87.254 Second VM cannot join domain. When I try it with domain WM I'm propmted for credentials. And I enter Administrator credentials and than it waits for some time and I get response: "The specified domain either does not exist or could not be contacted" If i type wm.local as domain when trying to join it does not prompt me to login but just shows "An Active Directory Domain Controller (AD DC) for the domain wm.local could not be contacted. And here it takes no time to get this error message. Ipconfig on this machine: IP: 192.168.87.134 Def Gataway: 192.168.87.2 DNS server: 192.168.87.2 DHCP server: 192.168.87.254 I can ping second VM from first one. And I disabled firewalls on both machines. Any ideas? Is there any manual for this?

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• Ubuntu 12.04 as router with 2 nic

  - by Blue Gene

  I have been trying this setup for weeks and still can not make this to work... ubuntu 12.04 64 bit with 2 nic nic1: eth0:192.168.2.33 -static ip with internet access (connected to modem) nic2: eth1:192.168.1.2 -static ip connected to LAN. enabled ip_forward on ubuntu box net_ip_forward = 1 on the LAN with ip address 192.168.1.5 specified gateway as 192.168.1.2 and able to ping gateway.But can not ping public address.What am i missing? on router box: route -n Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.2.1 0.0.0.0 UG 100 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 tried ip route add 192.168.2.0/24 via 192.168.1.2 dev eth0 route -n on LAN 192.168.1.5 Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.2 0.0.0.0 UG 100 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.2.0 192.168.1.2 255.255.255.0 UG 0 0 0 eth0 iptables default policy is to accept all. tracepath 8.8.8.8 from LAN 1: 192.168.1.5 0.060ms pmtu 1500 1: 192.168.1.2 3.367ms 1: 192.168.1.2 3.764ms 2: no reply Is there a way to make this work,other than NAT ing.

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• cheap gigabit switch for small business

  - by neoice

  my friend's business is currently borrowing my Adtran 1224R and is very happy with it. it's configured with a few VLANs to segment customers, internal traffic and public wifi. port 1 is a "trunk" port to the router, a chunky Linux box with iptables+NAT. they push a lot of traffic over the LAN (data backups) and really need gigabit. besides, I'd like my Adtran back :P my goal is to find a cheap(ish) switch that can function as a drop-in replacement. it looks like VLAN trunking is actually part of the 802.1q spec, so anything with VLAN support should cover the current trunk-to-router setup. it's nice to have both a web interface and SSH, but I can configure it either way if needed. things like the Netgear GS724T have caught my eye, but it seems like none of the hardware in the $300-500 range have really solid reviews. I'm concerned that "cheaper" hardware might not work for a network full of power users. does anyone have a recommendation for the Netgear GS724T or a switch that will meet my needs?

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• Service redirection on same network

  - by Unode

  I have a network on which I run multiple servers each dedicated to a given service. Because most services run on distinct ports I'm currently looking for a way of unifying "all" services into a single "proxy" machine. The idea is to abstract which machine is being accessed but still allow direct connection if needed/requested. This "proxy" machine has only one network interface which is part of the same network as all the other service providing machines. I've looked into Routing and NAT but I've so far failed to figure out how to make it work. I tried to achieve this using shorewall but couldn't find clear examples. However I'm not entirely sure this is the best/simplest strategy. With that said, what would be the best way of achieving this result? Example case: Proxy IP - Listening port - Send requests to 192.168.0.50 80 192.168.0.1:80 " 22 192.168.0.2:2222 " 3306 192.168.0.3:3000 " 5432 192.168.0.4:5432 " 5222 192.168.0.5:5222 PS: I'm not concerned with the single-point-of-failure nature of the proxy. Thanks

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• Can I use squid (or anything) to do this?

  - by user269334

  I have a really crappy VPS, and a really good computer at my office (with a really good internet connection), but behind a NAT. Is it possible to expose my good computer by doing this: 1. The good computer connects to the VPS (and keeps the connection alive) 2. The users connects to the VPS, and sends http(s) requests to the VPS. 3. The VPS just passes that http(s) requests to the good computer (including some identifications, so the servers can distinguish connections) 4. The good computer passes that http(s) response to the VPS 5. In turn, the VPS receives the http(s) response, and passes back to the client. Is it possible to do this? (btw, the VPS and the good computer are located in different countries) And also, is this "reverse proxy"? I heard that reverse proxy is for protecting the internal network by putting a middle server. And will this affect SSL configurations? (or make SSL impossible?) I'm intending to run nginx on the good computer. Thanks in advance : )

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• IPTables Reroute SSH based on Connection string?

  - by senrabdet

  We are using a cloud server (Debian Squeeze) where public ports on a public IP route traffic to internal servers. We are looking for a way to use IPTables and ssh where based on some part of the ssh connection string (or something along these lines) iptables will reroute the ssh connection to the "right" internal server. This would allow us to use one common public port, and then re-route ssh connections to individual servers. So, for example we hope to do something like the following: user issues ssh connection (public key encryption) such as ssh -X -v -p xxx [email protected] but maybe adds something into the string for iptables to use iptables uses some part of that string or some means to re-route the connection to an internal server using something like iptables -t nat -A PREROUTING ! -s xxx.xxx.xxx.0/24 -m tcp -p tcp --dport $EXTPORT -j DNAT --to-destination $HOST:$INTPORT ....where $HOST is the internal ip of a server, $EXTPORT is the common public facing port and $INTPORT is the internal server port. It appears that the "string" aspect of iptables does not do what we want. We can currently route based on the IP table syntax we're using, but rely on having a separate public port for each server and are hoping to use one common public port and then re-route to specific internal servers based on some part of the ssh connection string or some other means. Any suggestions? Thanks!

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• ubuntu 12.04 kvm virtual server network setup, can't get the machine to be connectable

  - by xyious

  I have worked on my Ubuntu Server host for weeks now and I just can not manage to get the virtual machines into the network.... here's what I need to do: I need to be able to create virtual machines that have IP addresses that can be reached from the outside (192.168 network). I need to be able to connect to the virtual machines through ssh, ftp, http and preferably https, anything else doesn't matter that much. So far everything seems simple enough and I have a lot of leeway in terms of IP address range and server/client configuration. I have the option of taking part of a /24 net as most IPs aren't used, and if it's absolutely necessary I have the option of creating a new /24 subnet. Also have the option of reformatting and reinstalling OS on the host and recreating the virtual machines as nothing has been done other than trying to get virtual machines to work. I would prefer if the virtual machines were just part of the normal network which would be 192.168.5.0/24. The host machine has 2 network cards so I don't even necessarily need the Host to be connectable in the same /24 network. I have tried (I think) just about everything from about 5 different tutorials on bridging (giving br0 the same IP that eth0 used to have (Host is able to connect to VM and vice versa, VM doesn't have outside network access), having eth0 set up like it always was and having br0 have a different IP (same as above), NAT with port forwarding (which I would have preferred not to use but will if it works), turning off one of the hosts network cards and just using one of them, different subnets.... etc. I do know my way around iptables fairly well.... Host is 64bit Ubuntu Server 12.04, using libvirt/kvm. edits: Local network is 192.168.5.0/24, host has static ip 192.168.5.254, GW .5.1 which is also nameserver. We have a second Local network at 192.168.10.0/24 with .10.1 GW, but both hosts and VMs were supposed to go into the .5 subnet. The .10 subnet isn't required, but it wouldn't be horrible if the Host were only accessible in the .10 subnet.

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• IPtables and Remote Desktop with Proxy

  - by Sebastian

  So I setup a windows 2008 web server R2 on VirtualBox. Currently using Bridged Network. I can remote desktop to the machine hosting the VM (10.0.0.183) but cannot remote desktop to the VM itself (10.0.0.195). The remote port on the VM set to 5003. VM setup to accept remote connections (windows side). We also use a proxy for our internet, and I added these rules under NAT. (centOS 5) on our proxy box. -A INPUT -p tcp --dport 3389 -j ACCEPT -A REROUTING -i ppp0 -p tcp --dport 3389 -j REDIRECT --to-port 5003 -A FORWARD -d 10.0.0.195 --dport 5003 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT I've been trying for hours and hours and just cannot get it to work. I also used freedns so that we can use a domain name to connect too this VM over the internet. (the DNS points to our external IP address). If we don't get this right we will have to purchase a PPoE from an ISP to connect to this VM remotely, but I know that there is an alternative route if I can just get this port forwarding right!

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• Asterisk relay between multiple subnets

  - by immoune

  I wonder what's the best way to go when you have phones on multiple networks which are not directly reachable. I have 3 networks 10.3.x.x 10.6.x.x 10.17.x.x My asterisk server resides on the 10.3.0.5 IP. The machines from the 10.6 and 10.17 networks are routed here through VPN tunnels. At this point we don't talk about NAT anywhere on the network just pure routing. Since the 10.3.0.5 PBX has routes back to all the subnet's it has no problem to communicate with softphones/hardphones from these ranges. The problem comes from that Asterisk (as far as I understand) only responsible for the SIP communication part not the Audio/Video transmission which is in P2P fashion done between the devices. So although a client using sipdroid from 10.6.x.x is able to connect to the pbx (10.3.0.5) and dial a bria client on the 10.17.x.x network once the phone rings out and the call establishes no audio will be transmitted simply because it has no way to directly connect there. For this there are multiple solutions described in this text: http://msdn.microsoft.com/en-us/library/ee480411%28v=winembedded.60%29.aspx What I would prefer is to keep these networks segregated as they are now. What would be the best solution? Is it possible to actually relay through all the audio/video information through the Asterisk server? That would be the best in my case, I using Astlinux there which has a lot of other parts. Thanks

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• oracle access on vmware fusion

  - by gaudi_br

  Hello, I'm running snow leopard and I'm doing some development that requires some network knowledge. I've installed vmware fusion 3.0 and I've set up a virtual machine with windows 2003 server. I need to mimic the exact configuration of another server in the network, so I really need to run the versions I'll be mentioning here. Besides, I set up two network configurations on the VM: one NAT config (so that I can have internet access) and one host-only config (because I need to use another server's mac adress and my local area network might have a problem with it) From the installation of windows 2003, I then installed oracle 10.2.0.1. During the installation I received a warning about the primary ip-address of the system being dhcp assigned, but I ignored it (maybe it was a mistake)... Now, from experience, unless the DHCP assigned address changes, I should be able to access the guest system's database from the host system, so I went to safari and tried to access the oracle em. As it turns out, because my computer is on a company network, the company's DNS doesn't know about the virtual machine, unless of course I switch to a bridged network config. However, I don't want to do that because I don't to mix up the domains. So I guess the question is, how can I define my own dns or router, or whatever it is that I need to define so that whenever I try the guest system's ip address form the host, it will use the vmnet1 or vmnet8 interface define by vmware and bypass the dns configuration of my local area network. I'd also like to know what to do incase I want to change ip addresses on the guest machine without having oracle go haywire (I've noticed a few folders on the structure which are specific for the very first IP Address)... Any help would be appreciated. Thanks in advance.

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• How do I tunnel an HTTPS proxy through a virtual machine (VMWare)

  - by Kyle

  I have a personal setup at home using VMWare Workstation. I also have a set of Virtual Private Machines that run Squid, and therefore provide me HTTPS proxy tunnels. Using Proxifier, I can tunnel all traffic for given applications through these tunnels. However, I also have a few virtual machines for dev/staging/experimentation/etc. I generally just use NAT to provide Internet access to the machines, and if I need to use these proxies, I can just setup Proxifier (or a Linux equivalent) to pipe the traffic through them. No problem. But... I got to thinking: Wouldn't it be great if I could assign these proxy tunnels to a virtual machine, so that when I start up the VM, it has instant-on access through the tunnel and not my local connection? (EDIT: Of course, it would USE my local connection, but it would tunnel traffic through the proxy.) To be more clear: I want a solution that binds the proxy to a VM, so that when I start the VM, I don't have to use a proxy client to connect to the tunnel - I am already piping all traffic from that VM through that proxy. I did a bit of searching, and the closest thing I could find was this: How to route public static IP to a virtual machine on a vmware ESXi host? Which wasn't all that applicable. The proxies are protected by user/pass but do not filter by IP. Again, they are HTTPS proxies setup through Squid. Any ideas on how to make this happen? Thanks a ton.

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• Print over the internet from a remote linux session locally (on a Windows 7 machine) to the shared printers?

  - by obeliksz

  I'm trying to use a linux virtual machine as a file server for windows clients. I have successfully implemented remote file sharing (samba+ssh) with which I am able to print locally with a little program that I made for this purpose (jetforms style)... but I would like to hear about a somewhat more direct approach. How can I attach the printers to the server, so that I can for example open a file on the remote session and in the print dialogbox I would see my local printers (on the machine from which I have established a remote session)? I guess there should be some kind of putty tunneling, but dont know how. I have a windows 7 machine locally; there is a CentOS 6 VM over the internet. It has ssh, cups, and samba. I have found a question which asks the opposite: there is a windows based server to connect form linux but that windows has a domain, mine is just a simple windows workstation that is behind NAT and has a dynamic IP. That question is: Print from Linux to Windows networked printer.

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• Software disables itself when the PC is accessed via RDP

  - by blckgrffn

  We have a large, specialty printer that has vendor specific software that enables its use outside of it showing up simply as a printer in the Windows Control Panel. This software recognizes when we RDP into the machine and "disconnects" the PC from the printer within its proprietary control panel. All is well when an application like TeamViewer is used to access the machine. Ostensibly, the application is helping us be safe by "enforcing" that the machine used for the printer is a walk up workstation, or so the support folks informed me. If TeamViewer etc, fixes the issue, then what is the problem? We have many headless workstations in our warehouse attached to a variety of specialty machines, all used via RDP. We want/need to keep access to the machines the same for the sanity of our production staff. The meat of the question - how, specifically, might a machine know that it is being accessed via RDP (terminal services management???) and how might this be defeated without altering an application or driver. Of note, the system being used is a Windows 7 Pro machine hooked to the printer via USB. Thanks! Nat edit Is there any combination of /admin switches, etc. that will possibly fix this? Simply putting /admin did not.

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• FreeBSD performance tuning. Sysctls, loader.conf, kernel

  - by SaveTheRbtz

  I wanted to share knowledge of tuning FreeBSD via sysctl.conf/loader.conf/KENCONF. It was initially based on Igor Sysoev's (author of nginx) presentation about FreeBSD tuning up to 100,000-200,000 active connections. Tunings are for FreeBSD-CURRENT. Since 7.2 amd64 some of them are tuned well by default. Prior 7.0 some of them are boot only (set via /boot/loader.conf) or does not exist at all. sysctl.conf: # No zero mapping feature # May break wine # (There are also reports about broken samba3) #security.bsd.map_at_zero=0 # If you have really busy webserver with apache13 you may run out of processes #kern.maxproc=10000 # Same for servers with apache2 / Pound #kern.threads.max_threads_per_proc=4096 # Max. backlog size kern.ipc.somaxconn=4096 # Shared memory // 7.2+ can use shared memory > 2Gb kern.ipc.shmmax=2147483648 # Sockets kern.ipc.maxsockets=204800 # Can cause this on older kernels: # http://old.nabble.com/Significant-performance-regression-for-increased-maxsockbuf-on-8.0-RELEASE-tt26745981.html#a26745981 ) kern.ipc.maxsockbuf=10485760 # Mbuf 2k clusters (on amd64 7.2+ 25600 is default) # For such high value vm.kmem_size must be increased to 3G kern.ipc.nmbclusters=262144 # Jumbo pagesize(_SC_PAGESIZE) clusters # Used as general packet storage for jumbo frames # can be monitored via `netstat -m` #kern.ipc.nmbjumbop=262144 # Jumbo 9k/16k clusters # If you are using them #kern.ipc.nmbjumbo9=65536 #kern.ipc.nmbjumbo16=32768 # For lower latency you can decrease scheduler's maximum time slice # default: stathz/10 (~ 13) #kern.sched.slice=1 # Increase max command-line length showed in `ps` (e.g for Tomcat/Java) # Default is PAGE_SIZE / 16 or 256 on x86 # This avoids commands to be presented as [executable] in `ps` # For more info see: http://www.freebsd.org/cgi/query-pr.cgi?pr=120749 kern.ps_arg_cache_limit=4096 # Every socket is a file, so increase them kern.maxfiles=204800 kern.maxfilesperproc=200000 kern.maxvnodes=200000 # On some systems HPET is almost 2 times faster than default ACPI-fast # Useful on systems with lots of clock_gettime / gettimeofday calls # See http://old.nabble.com/ACPI-fast-default-timecounter,-but-HPET-83--faster-td23248172.html # After revision 222222 HPET became default: http://svnweb.freebsd.org/base?view=revision&revision=222222 kern.timecounter.hardware=HPET # Small receive space, only usable on http-server, on file server this # should be increased to 65535 or even more #net.inet.tcp.recvspace=8192 # This is useful on Fat-Long-Pipes #net.inet.tcp.recvbuf_max=10485760 #net.inet.tcp.recvbuf_inc=65535 # Small send space is useful for http servers that serve small files # Autotuned since 7.x net.inet.tcp.sendspace=16384 # This is useful on Fat-Long-Pipes #net.inet.tcp.sendbuf_max=10485760 #net.inet.tcp.sendbuf_inc=65535 # Turn off receive autotuning # You can play with it. #net.inet.tcp.recvbuf_auto=0 #net.inet.tcp.sendbuf_auto=0 # This should be enabled if you going to use big spaces (>64k) # Also timestamp field is useful when using syncookies net.inet.tcp.rfc1323=1 # Turn this off on high-speed, lossless connections (LAN 1Gbit+) # If you set it there is no need in TCP_NODELAY sockopt (see man tcp) net.inet.tcp.delayed_ack=0 # This feature is useful if you are serving data over modems, Gigabit Ethernet, # or even high speed WAN links (or any other link with a high bandwidth delay product), # especially if you are also using window scaling or have configured a large send window. # Automatically disables on small RTT ( http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_subr.c?#rev1.237 ) # This sysctl was removed in 10-CURRENT: # See: http://www.mail-archive.com/[email protected]/msg06178.html #net.inet.tcp.inflight.enable=0 # TCP slowstart algorithm tunings # We assuming we have very fast clients #net.inet.tcp.slowstart_flightsize=100 #net.inet.tcp.local_slowstart_flightsize=100 # Disable randomizing of ports to avoid false RST # Before usage check SA here www.bsdcan.org/2006/papers/ImprovingTCPIP.pdf # (it's also says that port randomization auto-disables at some conn.rates, but I didn't checked it thou) #net.inet.ip.portrange.randomized=0 # Increase portrange # For outgoing connections only. Good for seed-boxes and ftp servers. net.inet.ip.portrange.first=1024 net.inet.ip.portrange.last=65535 # # stops route cache degregation during a high-bandwidth flood # http://www.freebsd.org/doc/en/books/handbook/securing-freebsd.html #net.inet.ip.rtexpire=2 net.inet.ip.rtminexpire=2 net.inet.ip.rtmaxcache=1024 # Security net.inet.ip.redirect=0 net.inet.ip.sourceroute=0 net.inet.ip.accept_sourceroute=0 net.inet.icmp.maskrepl=0 net.inet.icmp.log_redirect=0 net.inet.icmp.drop_redirect=1 net.inet.tcp.drop_synfin=1 # # There is also good example of sysctl.conf with comments: # http://www.thern.org/projects/sysctl.conf # # icmp may NOT rst, helpful for those pesky spoofed # icmp/udp floods that end up taking up your outgoing # bandwidth/ifqueue due to all that outgoing RST traffic. # #net.inet.tcp.icmp_may_rst=0 # Security net.inet.udp.blackhole=1 net.inet.tcp.blackhole=2 # IPv6 Security # For more info see http://www.fosslc.org/drupal/content/security-implications-ipv6 # Disable Node info replies # To see this vulnerability in action run `ping6 -a sglAac ::1` or `ping6 -w ::1` on unprotected node net.inet6.icmp6.nodeinfo=0 # Turn on IPv6 privacy extensions # For more info see proposal http://unix.derkeiler.com/Mailing-Lists/FreeBSD/net/2008-06/msg00103.html net.inet6.ip6.use_tempaddr=1 net.inet6.ip6.prefer_tempaddr=1 # Disable ICMP redirect net.inet6.icmp6.rediraccept=0 # Disable acceptation of RA and auto linklocal generation if you don't use them #net.inet6.ip6.accept_rtadv=0 #net.inet6.ip6.auto_linklocal=0 # Increases default TTL, sometimes useful # Default is 64 net.inet.ip.ttl=128 # Lessen max segment life to conserve resources # ACK waiting time in miliseconds # (default: 30000. RFC from 1979 recommends 120000) net.inet.tcp.msl=5000 # Max bumber of timewait sockets net.inet.tcp.maxtcptw=200000 # Don't use tw on local connections # As of 15 Apr 2009. Igor Sysoev says that nolocaltimewait has some buggy realization. # So disable it or now till get fixed #net.inet.tcp.nolocaltimewait=1 # FIN_WAIT_2 state fast recycle net.inet.tcp.fast_finwait2_recycle=1 # Time before tcp keepalive probe is sent # default is 2 hours (7200000) #net.inet.tcp.keepidle=60000 # Should be increased until net.inet.ip.intr_queue_drops is zero net.inet.ip.intr_queue_maxlen=4096 # Interrupt handling via multiple CPU, but with context switch. # You can play with it. Default is 1; #net.isr.direct=0 # This is for routers only #net.inet.ip.forwarding=1 #net.inet.ip.fastforwarding=1 # This speed ups dummynet when channel isn't saturated net.inet.ip.dummynet.io_fast=1 # Increase dummynet(4) hash #net.inet.ip.dummynet.hash_size=2048 #net.inet.ip.dummynet.max_chain_len # Should be increased when you have A LOT of files on server # (Increase until vfs.ufs.dirhash_mem becomes lower) vfs.ufs.dirhash_maxmem=67108864 # Note from commit http://svn.freebsd.org/base/head@211031 : # For systems with RAID volumes and/or virtualization envirnments, where # read performance is very important, increasing this sysctl tunable to 32 # or even more will demonstratively yield additional performance benefits. vfs.read_max=32 # Explicit Congestion Notification (see http://en.wikipedia.org/wiki/Explicit_Congestion_Notification) net.inet.tcp.ecn.enable=1 # Flowtable - flow caching mechanism # Useful for routers #net.inet.flowtable.enable=1 #net.inet.flowtable.nmbflows=65535 # Extreme polling tuning #kern.polling.burst_max=1000 #kern.polling.each_burst=1000 #kern.polling.reg_frac=100 #kern.polling.user_frac=1 #kern.polling.idle_poll=0 # IPFW dynamic rules and timeouts tuning # Increase dyn_buckets till net.inet.ip.fw.curr_dyn_buckets is lower net.inet.ip.fw.dyn_buckets=65536 net.inet.ip.fw.dyn_max=65536 net.inet.ip.fw.dyn_ack_lifetime=120 net.inet.ip.fw.dyn_syn_lifetime=10 net.inet.ip.fw.dyn_fin_lifetime=2 net.inet.ip.fw.dyn_short_lifetime=10 # Make packets pass firewall only once when using dummynet # i.e. packets going thru pipe are passing out from firewall with accept #net.inet.ip.fw.one_pass=1 # shm_use_phys Wires all shared pages, making them unswappable # Use this to lessen Virtual Memory Manager's work when using Shared Mem. # Useful for databases #kern.ipc.shm_use_phys=1 # ZFS # Enable prefetch. Useful for sequential load type i.e fileserver. # FreeBSD sets vfs.zfs.prefetch_disable to 1 on any i386 systems and # on any amd64 systems with less than 4GB of avaiable memory # For additional info check this nabble thread http://old.nabble.com/Samba-read-speed-performance-tuning-td27964534.html #vfs.zfs.prefetch_disable=0 # On highload servers you may notice following message in dmesg: # "Approaching the limit on PV entries, consider increasing either the # vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable" vm.pmap.shpgperproc=2048 loader.conf: # Accept filters for data, http and DNS requests # Useful when your software uses select() instead of kevent/kqueue or when you under DDoS # DNS accf available on 8.0+ accf_data_load="YES" accf_http_load="YES" accf_dns_load="YES" # Async IO system calls aio_load="YES" # Linux specific devices in /dev # As for 8.1 it only /dev/full #lindev_load="YES" # Adds NCQ support in FreeBSD # WARNING! all ad[0-9]+ devices will be renamed to ada[0-9]+ # 8.0+ only #ahci_load="YES" #siis_load="YES" # FreeBSD 8.2+ # New Congestion Control for FreeBSD # http://caia.swin.edu.au/urp/newtcp/tools/cc_chd-readme-0.1.txt # http://www.ietf.org/proceedings/78/slides/iccrg-5.pdf # Initial merge commit message http://www.mail-archive.com/[email protected]/msg31410.html #cc_chd_load="YES" # Increase kernel memory size to 3G. # # Use ONLY if you have KVA_PAGES in kernel configuration, and you have more than 3G RAM # Otherwise panic will happen on next reboot! # # It's required for high buffer sizes: kern.ipc.nmbjumbop, kern.ipc.nmbclusters, etc # Useful on highload stateful firewalls, proxies or ZFS fileservers # (FreeBSD 7.2+ amd64 users: Check that current value is lower!) #vm.kmem_size="3G" # If your server has lots of swap (>4Gb) you should increase following value # according to http://lists.freebsd.org/pipermail/freebsd-hackers/2009-October/029616.html # Otherwise you'll be getting errors # "kernel: swap zone exhausted, increase kern.maxswzone" # kern.maxswzone="256M" # Older versions of FreeBSD can't tune maxfiles on the fly #kern.maxfiles="200000" # Useful for databases # Sets maximum data size to 1G # (FreeBSD 7.2+ amd64 users: Check that current value is lower!) #kern.maxdsiz="1G" # Maximum buffer size(vfs.maxbufspace) # You can check current one via vfs.bufspace # Should be lowered/upped depending on server's load-type # Usually decreased to preserve kmem # (default is 10% of mem) #kern.maxbcache="512M" # Sendfile buffers # For i386 only #kern.ipc.nsfbufs=10240 # FreeBSD 9+ # HPET "legacy route" support. It should allow HPET to work per-CPU # See http://www.mail-archive.com/[email protected]/msg03603.html #hint.atrtc.0.clock=0 #hint.attimer.0.clock=0 #hint.hpet.0.legacy_route=1 # syncache Hash table tuning net.inet.tcp.syncache.hashsize=1024 net.inet.tcp.syncache.bucketlimit=512 net.inet.tcp.syncache.cachelimit=65536 # Increased hostcache # Later host cache can be viewed via net.inet.tcp.hostcache.list hidden sysctl # Very useful for it's RTT RTTVAR # Must be power of two net.inet.tcp.hostcache.hashsize=65536 # hashsize * bucketlimit (which is 30 by default) # It allocates 255Mb (1966080*136) of RAM net.inet.tcp.hostcache.cachelimit=1966080 # TCP control-block Hash table tuning net.inet.tcp.tcbhashsize=4096 # Disable ipfw deny all # Should be uncommented when there is a chance that # kernel and ipfw binary may be out-of sync on next reboot #net.inet.ip.fw.default_to_accept=1 # # SIFTR (Statistical Information For TCP Research) is a kernel module that # logs a range of statistics on active TCP connections to a log file. # See prerelease notes http://groups.google.com/group/mailing.freebsd.current/browse_thread/thread/b4c18be6cdce76e4 # and man 4 sitfr #siftr_load="YES" # Enable superpages, for 7.2+ only # Also read http://lists.freebsd.org/pipermail/freebsd-hackers/2009-November/030094.html vm.pmap.pg_ps_enabled=1 # Usefull if you are using Intel-Gigabit NIC #hw.em.rxd=4096 #hw.em.txd=4096 #hw.em.rx_process_limit="-1" # Also if you have ALOT interrupts on NIC - play with following parameters # NOTE: You should set them for every NIC #dev.em.0.rx_int_delay: 250 #dev.em.0.tx_int_delay: 250 #dev.em.0.rx_abs_int_delay: 250 #dev.em.0.tx_abs_int_delay: 250 # There is also multithreaded version of em/igb drivers can be found here: # http://people.yandex-team.ru/~wawa/ # # for additional em monitoring and statistics use # sysctl dev.em.0.stats=1 ; dmesg # sysctl dev.em.0.debug=1 ; dmesg # Also after r209242 (-CURRENT) there is a separate sysctl for each stat variable; # Same tunings for igb #hw.igb.rxd=4096 #hw.igb.txd=4096 #hw.igb.rx_process_limit=100 # Some useful netisr tunables. See sysctl net.isr #net.isr.maxthreads=4 #net.isr.defaultqlimit=4096 #net.isr.maxqlimit: 10240 # Bind netisr threads to CPUs #net.isr.bindthreads=1 # # FreeBSD 9.x+ # Increase interface send queue length # See commit message http://svn.freebsd.org/viewvc/base?view=revision&revision=207554 #net.link.ifqmaxlen=1024 # Nicer boot logo =) loader_logo="beastie" And finally here is KERNCONF: # Just some of them, see also # cat /sys/{i386,amd64,}/conf/NOTES # This one useful only on i386 #options KVA_PAGES=512 # You can play with HZ in environments with high interrupt rate (default is 1000) # 100 is for my notebook to prolong it's battery life #options HZ=100 # Polling is goot on network loads with high packet rates and low-end NICs # NB! Do not enable it if you want more than one netisr thread #options DEVICE_POLLING # Eliminate datacopy on socket read-write # To take advantage with zero copy sockets you should have an MTU >= 4k # This req. is only for receiving data. # Read more in man zero_copy_sockets # Also this epic thread on kernel trap: # http://kerneltrap.org/node/6506 # Here Linus says that "anybody that does it that way (FreeBSD) is totally incompetent" #options ZERO_COPY_SOCKETS # Support TCP sign. Used for IPSec options TCP_SIGNATURE # There was stackoverflow found in KAME IPSec stack: # See http://secunia.com/advisories/43995/ # For quick workaround you can use `ipfw add deny proto ipcomp` options IPSEC # This ones can be loaded as modules. They described in loader.conf section #options ACCEPT_FILTER_DATA #options ACCEPT_FILTER_HTTP # Adding ipfw, also can be loaded as modules options IPFIREWALL # On 8.1+ you can disable verbose to see blocked packets on ipfw0 interface. # Also there is no point in compiling verbose into the kernel, because # now there is net.inet.ip.fw.verbose tunable. #options IPFIREWALL_VERBOSE #options IPFIREWALL_VERBOSE_LIMIT=10 options IPFIREWALL_FORWARD # Adding kernel NAT options IPFIREWALL_NAT options LIBALIAS # Traffic shaping options DUMMYNET # Divert, i.e. for userspace NAT options IPDIVERT # This is for OpenBSD's pf firewall device pf device pflog # pf's QoS - ALTQ options ALTQ options ALTQ_CBQ # Class Bases Queuing (CBQ) options ALTQ_RED # Random Early Detection (RED) options ALTQ_RIO # RED In/Out options ALTQ_HFSC # Hierarchical Packet Scheduler (HFSC) options ALTQ_PRIQ # Priority Queuing (PRIQ) options ALTQ_NOPCC # Required for SMP build # Pretty console # Manual can be found here http://forums.freebsd.org/showthread.php?t=6134 #options VESA #options SC_PIXEL_MODE # Disable reboot on Ctrl Alt Del #options SC_DISABLE_REBOOT # Change normal|kernel messages color options SC_NORM_ATTR=(FG_GREEN|BG_BLACK) options SC_KERNEL_CONS_ATTR=(FG_YELLOW|BG_BLACK) # More scroll space options SC_HISTORY_SIZE=8192 # Adding hardware crypto device device crypto device cryptodev # Useful network interfaces device vlan device tap #Virtual Ethernet driver device gre #IP over IP tunneling device if_bridge #Bridge interface device pfsync #synchronization interface for PF device carp #Common Address Redundancy Protocol device enc #IPsec interface device lagg #Link aggregation interface device stf #IPv4-IPv6 port # Also for my notebook, but may be used with Opteron device amdtemp # Same for Intel processors device coretemp # man 4 cpuctl device cpuctl # CPU control pseudo-device # Support for ECMP. More than one route for destination # Works even with default route so one can use it as LB for two ISP # For now code is unstable and panics (panic: rtfree 2) on route deletions. #options RADIX_MPATH # Multicast routing #options MROUTING #options PIM # Debug & DTrace options KDB # Kernel debugger related code options KDB_TRACE # Print a stack trace for a panic options KDTRACE_FRAME # amd64-only(?) options KDTRACE_HOOKS # all architectures - enable general DTrace hooks #options DDB #options DDB_CTF # all architectures - kernel ELF linker loads CTF data # Adaptive spining in lockmgr (8.x+) # See http://www.mail-archive.com/[email protected]/msg10782.html options ADAPTIVE_LOCKMGRS # UTF-8 in console (8.x+) #options TEKEN_UTF8 # FreeBSD 8.1+ # Deadlock resolver thread # For additional information see http://www.mail-archive.com/[email protected]/msg18124.html # (FYI: "resolution" is panic so use with caution) #options DEADLKRES # Increase maximum size of Raw I/O and sendfile(2) readahead #options MAXPHYS=(1024*1024) #options MAXBSIZE=(1024*1024) # For scheduler debug enable following option. # Debug will be available via `kern.sched.stats` sysctl # For more information see http://svnweb.freebsd.org/base/head/sys/conf/NOTES?view=markup #options SCHED_STATS If you are tuning network for maximum performance you may wish to play with ifconfig options like: # You can list all capabilities via `ifconfig -m` ifconfig [-]rxcsum [-]txcsum [-]tso [-]lro mtu In case you've enabled DDB in kernel config, you should edit your /etc/ddb.conf and add something like this to enable automatic reboot (and textdump as bonus): script kdb.enter.panic=textdump set; capture on; show pcpu; bt; ps; alltrace; capture off; call doadump; reset script kdb.enter.default=textdump set; capture on; bt; ps; capture off; call doadump; reset And do not forget to add ddb_enable="YES" to /etc/rc.conf Since FreeBSD 9 you can select to enable/disable flowcontrol on your NIC: # See http://en.wikipedia.org/wiki/Ethernet_flow_control and # http://www.mail-archive.com/[email protected]/msg07927.html for additional info ifconfig bge0 media auto mediaopt flowcontrol PS. Also most of FreeBSD's limits can be monitored by # vmstat -z and # limits PPS. variety of network counters can be monitored via # netstat -s In FreeBSD-9 netstat's -Q option appeared, try following command to display netisr stats # netstat -Q PPPS. also see # man 7 tuning PPPPS. I wanted to thank FreeBSD community, especially author of nginx - Igor Sysoev, nginx-ru@ and FreeBSD-performance@ mailing lists for providing useful information about FreeBSD tuning. FreeBSD WIP * Whats cooking for FreeBSD 7? * Whats cooking for FreeBSD 8? * Whats cooking for FreeBSD 9? So here is the question: What tunings are you using on yours FreeBSD servers? You can also post your /etc/sysctl.conf, /boot/loader.conf, kernel options, etc with description of its' meaning (do not copy-paste from sysctl -d). Don't forget to specify server type (web, smb, gateway, etc) Let's share experience!

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• Linux router: ping doesn't route back

  - by El Barto

  I have a Debian box which I'm trying to set up as a router and an Ubuntu box which I'm using as a client. My problem is that when the Ubuntu client tries to ping a server on the Internet, all the packets are lost (though, as you can see below, they seem to go to the server and back without problem). I'm doing this in the Ubuntu Box: # ping -I eth1 my.remote-server.com PING my.remote-server.com (X.X.X.X) from 10.1.1.12 eth1: 56(84) bytes of data. ^C --- my.remote-server.com ping statistics --- 13 packets transmitted, 0 received, 100% packet loss, time 12094ms (I changed the name and IP of the remote server for privacy). From the Debian Router I see this: # tcpdump -i eth1 -qtln icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 305, seq 7, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 305, seq 8, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 305, seq 8, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 305, seq 9, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 305, seq 9, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 305, seq 10, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 305, seq 10, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 305, seq 11, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 305, seq 11, length 64 ^C 9 packets captured 9 packets received by filter 0 packets dropped by kernel # tcpdump -i eth2 -qtln icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth2, link-type EN10MB (Ethernet), capture size 65535 bytes IP 192.168.1.10 > X.X.X.X: ICMP echo request, id 360, seq 213, length 64 IP X.X.X.X > 192.168.1.10: ICMP echo reply, id 360, seq 213, length 64 IP 192.168.1.10 > X.X.X.X: ICMP echo request, id 360, seq 214, length 64 IP X.X.X.X > 192.168.1.10: ICMP echo reply, id 360, seq 214, length 64 IP 192.168.1.10 > X.X.X.X: ICMP echo request, id 360, seq 215, length 64 IP X.X.X.X > 192.168.1.10: ICMP echo reply, id 360, seq 215, length 64 IP 192.168.1.10 > X.X.X.X: ICMP echo request, id 360, seq 216, length 64 IP X.X.X.X > 192.168.1.10: ICMP echo reply, id 360, seq 216, length 64 IP 192.168.1.10 > X.X.X.X: ICMP echo request, id 360, seq 217, length 64 IP X.X.X.X > 192.168.1.10: ICMP echo reply, id 360, seq 217, length 64 ^C 10 packets captured 10 packets received by filter 0 packets dropped by kernel And at the remote server I see this: # tcpdump -i eth0 -qtln icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 1, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 1, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 2, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 2, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 3, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 3, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 4, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 4, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 5, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 5, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 6, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 6, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 7, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 7, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 8, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 8, length 64 IP Y.Y.Y.Y > X.X.X.X: ICMP echo request, id 360, seq 9, length 64 IP X.X.X.X > Y.Y.Y.Y: ICMP echo reply, id 360, seq 9, length 64 18 packets captured 228 packets received by filter 92 packets dropped by kernel Here "X.X.X.X" is my remote server's IP and "Y.Y.Y.Y" is my local network's public IP. So, what I understand is that the ping packets are coming out of the Ubuntu box (10.1.1.12), to the router (10.1.1.1), from there to the next router (192.168.1.1) and reaching the remote server (X.X.X.X). Then they come back all the way to the Debian router, but they never reach the Ubuntu box back. What am I missing? Here's the Debian router setup: # ifconfig eth1 Link encap:Ethernet HWaddr 94:0c:6d:82:0d:98 inet addr:10.1.1.1 Bcast:10.1.1.255 Mask:255.255.255.0 inet6 addr: fe80::960c:6dff:fe82:d98/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:105761 errors:0 dropped:0 overruns:0 frame:0 TX packets:48944 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:40298768 (38.4 MiB) TX bytes:44831595 (42.7 MiB) Interrupt:19 Base address:0x6000 eth2 Link encap:Ethernet HWaddr 6c:f0:49:a4:47:38 inet addr:192.168.1.10 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::6ef0:49ff:fea4:4738/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:38335992 errors:0 dropped:0 overruns:0 frame:0 TX packets:37097705 errors:0 dropped:0 overruns:0 carrier:1 collisions:0 txqueuelen:1000 RX bytes:4260680226 (3.9 GiB) TX bytes:3759806551 (3.5 GiB) Interrupt:27 eth3 Link encap:Ethernet HWaddr 94:0c:6d:82:c8:72 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:20 Base address:0x2000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:3408 errors:0 dropped:0 overruns:0 frame:0 TX packets:3408 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:358445 (350.0 KiB) TX bytes:358445 (350.0 KiB) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.8.0.1 P-t-P:10.8.0.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:2767779 errors:0 dropped:0 overruns:0 frame:0 TX packets:1569477 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:3609469393 (3.3 GiB) TX bytes:96113978 (91.6 MiB) # route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.8.0.2 0.0.0.0 255.255.255.255 UH 0 0 0 tun0 127.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 lo 10.8.0.0 10.8.0.2 255.255.255.0 UG 0 0 0 tun0 192.168.1.0 0.0.0.0 255.255.255.0 U 1 0 0 eth2 10.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth2 # arp -n # Note: Here I have changed all the different MACs except the ones corresponding to the Ubuntu box (on 10.1.1.12 and 192.168.1.12) Address HWtype HWaddress Flags Mask Iface 192.168.1.118 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.72 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.94 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.102 ether NN:NN:NN:NN:NN:NN C eth2 10.1.1.12 ether 00:1e:67:15:2b:f0 C eth1 192.168.1.86 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.2 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.61 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.64 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.116 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.91 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.52 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.93 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.87 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.92 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.100 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.40 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.53 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.1 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.83 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.89 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.12 ether 00:1e:67:15:2b:f1 C eth2 192.168.1.77 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.66 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.90 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.65 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.41 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.78 ether NN:NN:NN:NN:NN:NN C eth2 192.168.1.123 ether NN:NN:NN:NN:NN:NN C eth2 # iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination # iptables -L -n -t nat Chain PREROUTING (policy ACCEPT) target prot opt source destination Chain POSTROUTING (policy ACCEPT) target prot opt source destination MASQUERADE all -- 10.1.1.0/24 !10.1.1.0/24 MASQUERADE all -- !10.1.1.0/24 10.1.1.0/24 Chain OUTPUT (policy ACCEPT) target prot opt source destination And here's the Ubuntu box: # ifconfig eth0 Link encap:Ethernet HWaddr 00:1e:67:15:2b:f1 inet addr:192.168.1.12 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::21e:67ff:fe15:2bf1/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:28785139 errors:0 dropped:0 overruns:0 frame:0 TX packets:19050735 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:32068182803 (32.0 GB) TX bytes:6061333280 (6.0 GB) Interrupt:16 Memory:b1a00000-b1a20000 eth1 Link encap:Ethernet HWaddr 00:1e:67:15:2b:f0 inet addr:10.1.1.12 Bcast:10.1.1.255 Mask:255.255.255.0 inet6 addr: fe80::21e:67ff:fe15:2bf0/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:285086 errors:0 dropped:0 overruns:0 frame:0 TX packets:12719 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:30817249 (30.8 MB) TX bytes:2153228 (2.1 MB) Interrupt:16 Memory:b1900000-b1920000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:86048 errors:0 dropped:0 overruns:0 frame:0 TX packets:86048 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:11426538 (11.4 MB) TX bytes:11426538 (11.4 MB) # route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 0.0.0.0 10.1.1.1 0.0.0.0 UG 100 0 0 eth1 10.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 10.8.0.0 192.168.1.10 255.255.255.0 UG 0 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0 # arp -n # Note: Here I have changed all the different MACs except the ones corresponding to the Debian box (on 10.1.1.1 and 192.168.1.10) Address HWtype HWaddress Flags Mask Iface 192.168.1.70 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.90 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.97 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.103 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.13 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.120 (incomplete) eth0 192.168.1.111 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.118 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.51 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.102 (incomplete) eth0 192.168.1.64 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.52 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.74 (incomplete) eth0 192.168.1.94 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.121 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.72 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.87 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.91 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.71 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.78 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.83 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.88 (incomplete) eth0 192.168.1.82 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.98 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.100 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.93 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.73 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.11 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.85 (incomplete) eth0 192.168.1.112 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.89 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.65 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.81 ether NN:NN:NN:NN:NN:NN C eth0 10.1.1.1 ether 94:0c:6d:82:0d:98 C eth1 192.168.1.53 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.116 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.61 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.10 ether 6c:f0:49:a4:47:38 C eth0 192.168.1.86 (incomplete) eth0 192.168.1.119 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.66 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.1 ether NN:NN:NN:NN:NN:NN C eth0 192.168.1.1 ether NN:NN:NN:NN:NN:NN C eth1 192.168.1.92 ether NN:NN:NN:NN:NN:NN C eth0 # iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination # iptables -L -n -t nat Chain PREROUTING (policy ACCEPT) target prot opt source destination Chain INPUT (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain POSTROUTING (policy ACCEPT) target prot opt source destination Edit: Following Patrick's suggestion, I did a tcpdump con the Ubuntu box and I see this: # tcpdump -i eth1 -qtln icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 1, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 1, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 2, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 2, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 3, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 3, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 4, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 4, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 5, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 5, length 64 IP 10.1.1.12 > X.X.X.X: ICMP echo request, id 21967, seq 6, length 64 IP X.X.X.X > 10.1.1.12: ICMP echo reply, id 21967, seq 6, length 64 ^C 12 packets captured 12 packets received by filter 0 packets dropped by kernel So the question is: if all packets seem to be coming and going, why does ping report 100% packet loss?

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