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• Specific DNS sometimes resolves to wildcard, incorrectly

  - by Mojo

  I have an intermittent problem, and I'm not sure where to start trying to troubleshoot it. In our dev environment, we have two visible IP addresses on load balancers, one to the front-end, and one to a number of back-end service machines. The front-end is configured to take a wildcard DNS name to support generic "portals." dev.example.com A 10.1.1.1 *.dev.example.com CNAME dev.example.com The back-end servers are all specific names within the same space: core.dev.example.com A 10.1.1.2 cms.dev.example.com CNAME core.dev.example.com search.dev.example.com CNAME core.dev.example.com Here's the problem. Periodically a developer or a program trying to reach, say, cms.dev.example.com will get a result that points to the front-end, instead of the back-end load balancer: cms.dev.example.com is an alias to core.dev.example.com core.dev.example.com is an alias to dev.example.com (WRONG!) dev.example.com 10.1.1.1 The developers are all on Mac OS X machines, though I've seen the problem occur on an Ubuntu machine as well, using a local cloud host DNS resolver. Sometimes the developer is using a VPN, which directs the DNS to its own resolver, and sometimes he's on the local net using a DNS resolver assigned by the NAT router. Sometimes clearing the Mac OS X DNS cache, logging into the VPN, then logging out of the VPN, will make the problem go away. The origin authoritative server is on zerigo, and a dig directly to their name servers always seems to give the correct answer. The published DNS cache time for these records is 15 minutes, but the problem has been intermittent for about a week. Any troubleshooting suggestions?

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• Cisco ASA user authentication options - OpenID, public RSA sig, others?

  - by Ryan

  My organization has a Cisco ASA 5510 which I have made act as a firewall/gateway for one of our offices. Most resources a remote user would come looking for exist inside. I've implemented the usual deal - basic inside networks with outbound NAT, one primary outside interface with some secondary public IPs in the PAT pool for public-facing services, a couple site-to-site IPSec links to other branches, etc. - and I'm working now on VPN. I have the WebVPN (clientless SSL VPN) working and even traversing the site-to-site links. At the moment I'm leaving a legacy OpenVPN AS in place for thick client VPN. What I would like to do is standardize on an authentication method for all VPN then switch to the Cisco's IPSec thick VPN server. I'm trying to figure out what's really possible for authentication for these VPN users (thick client and clientless). My organization uses Google Apps and we already use dotnetopenauth to authenticate users for a couple internal services. I'd like to be able to do the same thing for thin and thick VPN. Alternatively a signature-based solution using RSA public keypairs (ssh-keygen type) would be useful to identify user@hardware. I'm trying to get away from legacy username/password auth especially if it's internal to the Cisco (just another password set to manage and for users to forget). I know I can map against an existing LDAP server but we have LDAP accounts created for only about 10% of the user base (mostly developers for Linux shell access). I guess what I'm looking for is a piece of middleware which appears to the Cisco as an LDAP server but will interface with the user's existing OpenID identity. Nothing I've seen in the Cisco suggests it can do this natively. But RSA public keys would be a runner-up, and much much better than standalone or even LDAP auth. What's really practical here?

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• Network to network VPN Centos 5

  - by Atul Kulkarni

  I am trying to follow "http://www.centos.org/docs/5/html/Deployment_Guide-en-US/ch-vpn.html#s1-ipsec-net2net" I have come up with the following On local router machine: in my ifcfg-ipsec0: ONBOOT=yes IKE_METHOD=PSK DSTGW=10.5.27.1 SRCGW=10.6.159.1 DSTNET=10.5.27.0/25 SRCNET=10.6.159.0/24 DST=205.X.X.X TYPE=IPSEC I have /etc/sysconfig/network-scripts/keys-ipsec0 file in place. On Remote Machine in the cloud if have /etc/sysconfig/network-scripts/ifcfg-ipsec1: TYPE=IPSEC ONBOOT=yes IKE_METHOD=PSK SRCGW=10.5.27.1 DSTGW=10.6.159.1 SRCNET=10.5.27.124/25 DSTNET=10.6.159.0/24 DST=38.x.x.x with its respective /etc/sysconfig/network-scripts/key-ipsec1 file. The DST in both cases are NAT'd external IPs. Is that a problem? I have made changes for port forwarding as well. When I try to bring the interfaces up it gives me output "RTNETLINK answers: Invalid argument". I am confused now and don't know what more to do? Any place I can digup what parameters were wrong? I really appreciate any help I can get. Thanks and Regards, Atul.

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• What is the IPv6 equivalent to IPv4 RFC1918 addresses?

  - by Kumba

  Having a hard time wrapping my head around IPv6 here. A lot of the lingo seems targeted at enterprise-level IPv6 deployments, discussing link-local, site-local, global unicast, scopes, etc. Not a lot of solid information on really small networks, like home networks. I want to check my thinking and make sure I am getting the correct translations from IPv4-speak to IPv6-speak. The first question is, what's the equivalent of RFC1918 for IPv6? Initial searches suggested there was no equivalent. Then I stumbled upon Unique Local Addresses (RFC4193), and that states that all ULA's should be assigned the prefix fc00, followed by a 40-bit random number in the routing prefix. This random number is to "prevent collisions when two IPv6 networks are interconnected" -- again, another reference to an enterprise-level function. If I have a small local LAN at home, numbered using 192.168.4.0/24, what's my equivalent in IPv6's ULA scope? Assuming I will never, ever, tie that IPv6 address into the real internet (a router will NAT & firewall it), can I ignore the RFC to an extent and go with fc00::4:0/120? It also seems that any address in fc00::/7 are to be globally routable. Does this mean I'll need extra protections so my router would not automatically start advertising these private IPv6 addresses to the world? Second question, what's this link-local thing? Reading suggests a default-assigned address in the fe80::/10 range that has the last 64bits of the address comprised of the interface's MAC address. Seems to be required, too, but I'm annoyed by the constant discussion of it in relation to enterprise networks. Third question, what is scope id for? Seems to be yet another term tossed around in relation to enterprise networks, especially when interconnecting them, but almost no explanation on the smaller home network level. Can I see a scope ID AND CIDR notation used together? I.e., fc00::4:0/120%6, or are scope IDs only supposed to be applied to a single /128 IPv6 address?

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• How to set up port forwarding on a dedicated server running CentOS 5.4 to use Ubuntu 9.0.4

  - by mairtinh

  The basic situation that I have is a dedicated server running CentOS 5.4 At the moment I have one VM running Ubuntu 9.0.4. Later on, I will want to add another VM running Windows Server 2003 but at the moment I am focusing on getting Ubuntu up and running. The Ubuntu installation is working fine but I'm seriously struggling to get port forwarding working so that I can access websites to be hosted on the Ubuntu VM. As a newbie to Linux, I am confused about the relationship between IPTables and VMWare's own port forwarding. Here's what I've tried so far. The IP of my server is xxx.xxx.xxx.xxx and the provider support have told me that the subnet mask is 255.255.255.0, the gateway address is xxx.xxx.xxx.1 and the network address is xxx.xxx.xxx.0. (Those latter two surprise me a bit, I expected private gateway/network address rather than public ones.) First of all I tried Bridged Networking but had no success at all in communicating with the machine other than through the VMware console. I tried pinging it from the host (using ssh into the host) but no joy; also no Inernet access from the VM. I changed the interfaces configuration from DHCP to Static, using a static address of 192.168.1.100 and setting the gateway to xxx.xxx.xxx.1 as advised by the provider. No real difference, still cannot ping the guest from the host or vice versa and no Internet access from the guest. Then I tried NAT. The host automatically set the IP address to 192.168.132.128 with a gateway of 192.168.132.2 Now the guest has Internet access out and when I do a VNC to the host and open Firefox with 192.168.132.128 I can see the hosted website okay but I still cannot get into it from outside. I mentioned that I'm a bit confused about IPtables and VMware port forwarding, what I meant is that I'm not sure whether IPtable forwarding should be set to the IP address of the guest interface (192.168.132.128 in this case) or the gateway address 192.168.132.2 . I have a feeling that I'm missing something very simple here, can anybody tell me what it is?

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• SSH through standard Belkin router to Asus Tomato router

  - by Luke

  I've set up SSH on the Tomato firmware on an Asus N10, via port 22 with key authentication. I've tested the keys by connecting with putty directly to the router when connected to its network. That works OK. But this router is behind a Belkin (F5D7632-4) router which also acts as modem and when I try to connect through with the (dynamic) public IP it times out. I'm guessing it's something to do with the NAT? My putty settings are taken from various online tutorials, but it's set up for port 22, with the correct key as mentioned. The Belkin router has port forwarding to the Asus (192.168.2.3) for port 22 TCP and UDP set up. It's now tough to see what to do in order to connect to the Asus router with an external IP - if it's even possible. Ideally I would have liked to have only needed to use the Asus router, but as it doesn't act as a modem, I need to connect it to the Belkin to use Tomato's features. Perhaps there's a solution here too? Network: Internet -> Belkin modem/router -> Asus router (Tomato SSH) -> Devices

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• RDP or SSH connection trough Windows 2008 server VPN hang after a while

  - by xt4fs

  I have been experiencing a very strange issue with our VPN setup on Windows Server 2008. That server is running as a Xen Virtual Machine. We use it for two purposes, permit our mobile workers to connect to another server hosted somewhere else that only allow that ip, and use it to RDP or ssh to many other virtual machine on the same server. The server has no performance issue and still a load of memory free. All other virtual machine has no problem whatsoever. Many of those virtual machine have public IP (web servers) and all their firewall are set to allow only ssh connection or RDP connection from their local interface. When I am connecting directly with either ssh or RDP to one of the other virtual machine everything run without any issues. However, when I am doing so through the VPN after some time the connection just hang, it usually continue after some time (5 or 10 minutes). It seems as more there is network usage more often it happen to a point where it is completely unusable. The worst thing I can do to hang it faster is to actually ping the vpn client IP from the local network, after some time the latency increase until it hang. This happen even if I do RDP to the local ip of the VPN server trough the VPN. The server report no problem and if I disconnect to the vpn and reconnect right away everything is alright. There is nothing wrong in the VPN server log. I have taught at the beginning that it could have been an issue with the Host server so I try to RDP,ssh directly to the guest and I have experience no issue while doing this, so it really seems to be a problem with the VPN server on Windows server 2008. Another very weird thing is it does not seems to be of any issue if you only do Internet (NAT) without trying to connect to any local ips.

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• asterisk extensions.conf & sip.conf

  - by Josh

  I'm trying to get my Dialplan to work. When I call, the only thing I get is a dial tone to enter extension "no Background(thanks-calling) is played". When extension 123 is dialed, busy signal is triggered and asterisk CLI get frozen. Any help will be appreciate it. Conf files below. ; PSTN on sip.conf [pstn] type=friend host=dynamic context=pstn username=pstn secret=password nat=yes canreinvite=no dtmfmode=rfc2833 qualify=yes insecure=port,invite disallow=all allow=ulaw ; PSTN on extensions.conf [pstn] exten => s,1,Answer exten => s,2,Wait,2 exten => s,4,DigitTimeout,5 exten => s,5,ResponseTimeout,10 exten => s,6,Background(thanks-calling) exten => 0,1,Goto(incoming,123,1) ; (Member Services) [incoming] exten => 123,1,NoOP(${CALLERID}) ; show the caller ID info in the console exten => 123,n,Ringing() exten => 123,n,Answer() exten => 123,n,Playback(silence/1) exten => 123,n,Playback(connecting1) exten => 123,n,Wait(3) exten => 123,n,Dial(SIP/line1,60) exten => 123,n,Congestion

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• RRAS Problem routing to central site from RRAS server only?

  - by TomTom

  Given is an office connected to headquarters using a RRAS bridge (2 virtual machines using RRAS to route between the two networks). Naming: The office is A, the RRAS on A is a-lnk. THe headquartters is B, b-lnk the RRAS machine there. The VPN works perfectly - machines can ping and work between the sites. Domain controllers on both ends replicating, DFS working, remote desktop working. All in all... everything is fine. EXCEPT: a-lnk itself can not reach any machine in B. This would normally not be troublesome (noone ever does anything on a-lnk), but there are two exceptions: * a-lnk is supposed to get it's license from a KMS in B, so not being able to reach B means it is not prolonging. * a-lnk is supposed to pull updates from a WSUS in B - and not being able to reach B means - no updates. Given that thigns work (and security is a minor issue - A-lnk is not reachable from the internet as it is behing a NAT hardware anyway) this got not handled for months. I just wan to get this item ticked off now. Anyone an idea what this is? It definitely is not a "dns does not work" or "routing in general is bad" item, as any computer in A can connect to any computer in B, and the other way arount - only the RRAS computer itself seems to do something really awkward. Platform for both: 2008 R2 standard.

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• How to diagnose remote assistance problem

  - by cantabilesoftware

  I have a long standing issue with remote assistance between a home and work PC. My wife and I both use MSN messenger and I used to be able to control her PC at home via MSN Remote Assistance. Some time ago however this stopped working and I don't know why. We're both running the latest versions of MSN Live Messenger and I've checked the appropriate firewall ports are open, but it still doesn't work and MSN just says something useless like "The person isn't responding". Any suggestions for how can I diagnose this? More info: I just tried direct Remote Desktop between work PC and home PC and it works fine - so I presume all the appropriate ports are open. Just Remote Assistance doesn't work. I'd like to get RA working so I can demonstrate how to do things remotely. With Remote Desktop the person at the other end gets booted off and can't see. With Remote Assistance they can follow along step by step. Some comments below suggest using other solutions, which is fine and do work, but there must be a way to diagnose RA and get it working. Experimenting with this some more, the notebook that I was using at work today that refused to connect works fine for remote assistance when I bring it home. So I guess this must be a problem with our network configuration at work. I've checked that 3389 is open on firewall on office router and remote desktop works both ways.... just not remote assistance. I've read that remote assitance won't work if client and server are both behind Non-UPnP/NAT routers. If one has UPnP it's supposed to work. Office router doesn't have UPnP enabled but my home one does. I've also scoured the event logs on both ends, nothing noteworthy - unless I'm looking in the wrong spot). Note (copied from comment): I've just tried ShowMyPC which is based on VNC and it works, but I'd still like to figure out what's wrong with RA - it's just bugging me. The question is only about Remote Assistance, no need to propose solutions based on other programs.[/edit by Gnoupi]

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• trying to figure out how to bridge two virtual networks together and in turn bridge that to the internet for a virtual inline IDS/IPS system

  - by Tony robinson

  I'm trying to figure out how to bridge two vmware (server or workstation, workstation) or virtualbox networks together with a linux IDS/IPS system transparently inline between both the virtual networks. How do I accomplish this? I understand how to bridge to virtual networks together, but how to I make the linux virtual machine sit between them and force traffic to go across the transparent bridge? I would like to have something along the lines of: vmnet a various vms host-only network ---- inline linux box vmnet a boxes forced to go through here to get to the internet --- vmnet b network with internet access configured as either NAT or bridged -- internet I know that basically the linux box needs two virtual nics, one on vmnet a and vmnet b, but other than that, I don't know how to force all the traffic to go across the "transparent" bridging linux box on its way to the internet. Do vmnet a and b have to be the same ip network with the same default route? does vmnet a not have a default route and vmnet b have a default route? I've read in vmware forums that on the linux host you need to change permissions on the vmnet files for promiscuous mode? is this true? how do you configure this scenario on a windows box?

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• Outbound mail issue during Exchange 2003 migration

  - by user27574

  Dear all, I am having an outbound email issue during the Exch 03 migration. Basically, we are migrating Exch03 to new hardware, both servers are Server 03 based. Everything runs smooth while setting up and installing Exch 03 on the new box. Public folders are all replicated. My issues are shown below.... 1) After starting to move users' mailboxes to new Exch 03, they receive some undeliverable mail and bounced back mail from some vendors, then I move few users back to test around, they have no problem at all after moving back to old Exch 03. 2) Another issue is our company has Blackberry users, we don't have BES. Under each user's mailboxes, we have forward rule setup, so that both user inbox and BB can receive email. User who is moved to the new Exch 03 server, they can only send email to the BB user's inbox, mail cannot be forwarded to BB at all, smtp queue stacks up and keep trying until the time is expired. Since not all emails that the users send out from the new Exch have problem, I am not able to narrow down what is the issue here. Can anyone give me some ideas? Could this be MX record / Reversed DNS relate? Or firewall NAT rule setting? Thanks.

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• How to make Virtualbox, OpenVPN, and Win2008 Web R2 like one another?

  - by Aquitaine

  Back with web developer guy wearing net admin hat. Hopefully this is an easy one. We have two servers on a public network at a hosted facility. Server A is our public-facing web server and server B is our database server. Both are running Windows 2008 Server R2 Web Edition. We want Server B isolated from everything except Server A, such that anyone who has to connect to server B goes through the VPN on Server A. It's not perfect since we have no access to do this on the router side, but it's what we've got. We've set up VirtualBox and OpenVPN Access Server on Server A. It has one network interface set to 'NAT' mode, such that OpenVPN gets its IP at 10.0.2.x, and to connect to the OpenVPN interface, I go to the local IP for the Virtualbox network adapter, 192.168.56.x, which works as I configured the appropriate ports using VBoxManage. My question is, do I need to be using Bridged Networking and give the VPN server its own IP, or is there some way to tell the server (either Windows or the Virtualbox OpenVPN) that 'any public connection on the real external IP on port X should be directed to this internal LAN address of 192.168.1.x on port Y'? OpenVPN itself doesn't seem to be aware of the server's real external IP unless we put it in Bridged networking mode; is that necessary or advisable? We're without RRAS since this is Web edition, but I feel like what we're going for is pretty simple. Thanks! Aq

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• When connecting to PPTP Centos via Windows 7 VPN, I get error 2147943625

  - by Charlie Dyason

  The remote computer refused the network connection. phrase has been my arch enemy for the past week now I recently "bought" a VPS server, I gave up trying to configure it with OpenVPN, all the issues were making me lose my mind, so I tried the easier way with pptp, but i figure, both are leading to a dead end... I followed this post (many others too but this is the unlucky one), http://blog.secaserver.com/2011/10/install-vpn-pptp-server-centos-6/ and it all goes well with the setup, however, I run into this error when connecting to the VPN in Windows 7 here is a pic of the error: Image So I do not know what I have done wrong... When connecting, Code: Select all netstat -apn | grep -w 1723 before connecting: netstat -apn |grep -w 1723 tcp 0 0 0.0.0.0:1723 0.0.0.0:* LISTEN 1137/pptpd after the error came I tried again: netstat -apn |grep -w 1723 tcp 0 0 0.0.0.0:1723 0.0.0.0:* LISTEN 1137/pptpd tcp 0 0 41.185.26.238:1723 41.13.212.47:49607 TIME_WAIT - iptables: # Generated by iptables-save v1.4.7 on Fri Nov 1 18:14:53 2013 *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [63:8868] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i eth0 -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 1723 -j ACCEPT -A INPUT -i eth0 -p gre -j ACCEPT -A FORWARD -i ppp+ -o eth0 -j ACCEPT -A FORWARD -i eth0 -o ppp+ -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT # Completed on Fri Nov 1 18:14:53 2013 # Generated by iptables-save v1.4.7 on Fri Nov 1 18:14:53 2013 *nat : PREROUTING ACCEPT [96:12732] : POSTROUTING ACCEPT [0:0] : OUTPUT ACCEPT [31:2179] -A POSTROUTING -o eth0 -j MASQUERADE COMMIT # Completed on Fri Nov 1 18:14:53 2013 options.pptpd the only changes was the require-mppe # BSD licensed ppp-2.4.2 upstream with MPPE only, kernel module ppp_mppe.o # {{{ refuse-pap refuse-chap refuse-mschap # Require the peer to authenticate itself using MS-CHAPv2 [Microsoft # Challenge Handshake Authentication Protocol, Version 2] authentication. require-mschap-v2 require-mppe # Require MPPE 128-bit encryption # (note that MPPE requires the use of MSCHAP-V2 during authentication) require-mppe-128 # }}} I check the iptables, everything is normal, all INPUTs, etc are before rejects, username and password I also checked in chap-secrets file, I am really puzzled...

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• Cisco IOS BVI ACL: Only allow established UDP

  - by George Bailey

  Related: Cisco IOS ACL: Don't permit incoming connections just because they are from port 80 I know we can use the established keyword for TCP.. but what can we do for UDP (short of replacing a Bridge or BVI with a NAT)? Answer I found out what "UDP has no connection" means. DNS uses UDP for example.. named (DNS server) is lisenting on port 53 nslookup (DNS client) starts listening on some random port and sends a packet to port 53 of the server and notes the source port in that packet. nslookup will retry 3 times if necessary. Also the packets are so small that it does not have to worry about them coming in the wrong order. If nslookup receives a response on that port that comes from the servers IP and port then it stops listening. If the server tried to send two responses (for example a response and a response to the retry) then the server would not care if either of them made it because the client has the job to retry. In fact.. unless ICMP 3/3 packet gets through the server would not know about a failure. This is different from TCP where you get connection closed or timed out errors. DNS allows for an easy retry from the client as well as small packets.. so UDP is an excellent choice because it is more efficient. In UDP you would see nslookup sends request named sends answer In TCP you would see nslookup's machine sends SYN named's machine sends SYN-ACK nslookup's machine sends ACK and the request named's machine sends the response That is much more than is necessary for a tiny DNS packet

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• DNS: how to get local server to superimpose results over authoritative server?

  - by growse

  I've got a domain for which the DNS I control, and is hosted on the internet. I also have a NAT'd internal network (192.168.0.0/24) which has internet access, and which I also control. On this internal network, I also have a DNS resolver. DNS software on both is PowerDNS. What I want to be able to do is for the DNS resolver on the internal network to be able to add/change records of queries and results that come down from the authoritative server. For example, the authoritative server might have a single record for animal.example.com: animal.example.com. IN AAAA 2001:140:283::1 However, I'd like it so that when internal clients do a dns lookup for animal.example.com, they might get back the following: animal.example.com. IN AAAA 2001:140:283::1 animal.example.com. IN A 192.168.0.2 Obviously, I could set up the internal DNS server to pretend to be authoritative for example.com, but that would require a fair bit of effort to keep the main DNS server and the internal DNS server in sync for the records which are the same between both. If the internal DNS server could somehow be made a slave of the main DNS server, but also have the provision to add its own results in, that would be ideal. Is this possible?

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• Blocking an IP in Webmin

  - by Dan J

  I've been checking my /var/log/secure log recently and have seen the same bot trying to brute force onto my Centos server running webmin. I created a chain + rule in Networking - Linux Firewall: Drop If source is 113.106.88.146 But I'm still seeing the attempted logins in the log: Jun 6 10:52:18 CentOS5 sshd[9711]: pam_unix(sshd:auth): check pass; user unknown Jun 6 10:52:18 CentOS5 sshd[9711]: pam_succeed_if(sshd:auth): error retrieving information about user larry Jun 6 10:52:19 CentOS5 sshd[9711]: Failed password for invalid user larry from 113.106.88.146 port 49328 ssh2 Here is the contents of /etc/sysconfig/iptables: # Generated by webmin *filter :banned-ips - [0:0] -A INPUT -p udp -m udp --dport ftp-data -j ACCEPT -A INPUT -p udp -m udp --dport ftp -j ACCEPT -A INPUT -p udp -m udp --dport domain -j ACCEPT -A INPUT -p tcp -m tcp --dport 20000 -j ACCEPT -A INPUT -p tcp -m tcp --dport 10000 -j ACCEPT -A INPUT -p tcp -m tcp --dport https -j ACCEPT -A INPUT -p tcp -m tcp --dport http -j ACCEPT -A INPUT -p tcp -m tcp --dport imaps -j ACCEPT -A INPUT -p tcp -m tcp --dport imap -j ACCEPT -A INPUT -p tcp -m tcp --dport pop3s -j ACCEPT -A INPUT -p tcp -m tcp --dport pop3 -j ACCEPT -A INPUT -p tcp -m tcp --dport ftp-data -j ACCEPT -A INPUT -p tcp -m tcp --dport ftp -j ACCEPT -A INPUT -p tcp -m tcp --dport domain -j ACCEPT -A INPUT -p tcp -m tcp --dport smtp -j ACCEPT -A INPUT -p tcp -m tcp --dport ssh -j ACCEPT -A banned-ips -s 113.106.88.146 -j DROP COMMIT # Completed # Generated by webmin *mangle :FORWARD ACCEPT [0:0] :INPUT ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :PREROUTING ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] COMMIT # Completed # Generated by webmin *nat :OUTPUT ACCEPT [0:0] :PREROUTING ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] COMMIT # Completed

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• Isolate clients on same subnet?

  - by stefan.at.wpf

  Given n (e.g. 200) clients in a /24 subnet and the following network structure: client 1 \ . \ . switch -- firewall . / client n / (in words: all clients connected to one switch and the switch connected to the firewall) Now by default, e.g. client 1 and client n can communicate directly using the switch, without any packets ever arriving the firewall. Therefore none of those packets could be filtered. However I would like to filter the packets between the clients, therefore I want to disallow any direct communication between the clients. I know this is possible using vlans, but then - according to my understanding - I would have to put all clients in their own network. However I don't even have that much IP addresses: I have about 200 clients, only a /24 subnet and all clients shall have public ip addresses, therefore I can't just create a private network for each of them (well, maybe using some NAT, but I'd like to avoid that). So, is there any way to tell the switch: Forward all packets to the firewall, don't allow direct communication between clients? Thanks for any hint!

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• SSH connection problem - allowed from LAN but not WAN

  - by Kerem Ulutas

  I tried to setup my Arch Linux installation to be an SSH host, but here is the thing: I can ssh localhost, it fails to login via public key and asks for username and password, but still able to login. When I try ssh my_wan_ip it gives ssh_exchange_identification: Connection closed by remote host error. I've read all topics about this error and none helped me. By the way, just confirmed, it gives ssh: connect to host my_dyndns_hostname port 22: Connection refused from another machine (outside of my network, it has different wan ip). I have sshd: ALL in "hosts.allow", ALL:ALL in "hosts.deny". I am able to connect to my own pc via ssh, ping my own pc, but my ssh setup seems to be the problem, it gives that annoying error when I try to ssh from wan. /etc/ssh/ssh_config /etc/ssh/sshd_config And finally, here is the debug output for both sshd and ssh: (i ran ssh command and i took output to sshd debug after that): sshd debug ssh debug I can edit my question according to your needs. Just ask for any more information needed. BTW I have no iptables running. I have one cable dsl modem connected to a asus wl-330gE wireless access point, they both have their firewall disabled. I configured NAT so port 22 is directed to the pc I'm having this trouble. Any help appreciated, thanks..

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• iptables configuration under ubuntu

  - by aioobe

  I'm following a tutorial on setting up a dns-tunnel. I've run into the following instruction: Now you need to enable forwarding on this server. I use iptables to implement masquerading. There are many HOWTOs about this (a simple one, for example). On Debian, the configuration file for iptables is in /var/lib/iptables/active. The relevant bit is: *nat :PREROUTING ACCEPT [6:1596] :POSTROUTING ACCEPT [1:76] :OUTPUT ACCEPT [1:76] -A POSTROUTING -s 10.0.0.0/8 -j MASQUERADE COMMIT Restart iptables: /etc/init.d/iptables restart The problem is that I don't have any /var/lib/iptables/active. (I'm on ubuntu.) How can I accomplish this? I suspect that I should just interact with the iptables command somehow but I have no clue what to write. Best would probably be if I could put the commands in a script somehow I suppose. (A side-note. If I execute a few iptables-commands it wont be there for ever, right? The rules will be discarded on reboot?)

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• Server 2003 and XP Client; Why are HTTP connections being silently dropped.

  - by Asa Yeamans

  On my network, my edge-router, a windows 2003 r2 server router with all the latest updates, will drop packets, but only under specific circumstances. I have troubleshot and isolated it down to the most simple configuration i can. There is NO NAT involved. Only fully-public IP addresses. No Firewalls are running either, all ahve been disabled. no packet filters on any interfaces anywhere either. I have a single Windows XP virtual machine and my edge-router(the windows 2003 r2 server, and also a virtual machine) running on a windows 2008 x64 r2 system (running virtual server 2005 as i dont have Intel-VT compatible chip yet). The edge router can access any external http site just fine, no issues. However the windows XP machine is only able to access certain sites. These work: www.google.com www.txstate.edu www.workintexas.com www.thedailywtf.com . These Dont: www.yahoo.com www.utexas.edu en.wikipedia.org slashdot.org www.bing.com. I have removed all possibility of DNS issues by connecting with net-cat from the XP box and sending GET /\r\nHost: \r\n\r\n and that connection replicates the issue as well. The network setup: My statically assigned IP block: x.x.x.168/29 DSL Modem -----PPPoE Connection---- x.x.x.169[EdgeRouter] [EdgeRouter]x.x.x.170 -----Virtual Ethernet----- x.x.x.174 [Test2] Test2's Default gateway is x.x.x.170 and test2 can ping any and every valid, accessible, public IP address with no packet loss what-so-ever. If i connect directly over PPPoE from test2 (the XP box) everything works just fine... Im at my wits end, i have NO IDEA whats causing this.

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• iptables to block non-VPN-traffic if not through tun0

  - by dacrow

  I have a dedicated Webserver running Debian 6 and some Apache, Tomcat, Asterisk and Mail-stuff. Now we needed to add VPN support for a special program. We installed OpenVPN and registered with a VPN provider. The connection works well and we have a virtual tun0 interface for tunneling. To archive the goal for only tunneling a single program through VPN, we start the program with sudo -u username -g groupname command and added a iptables rule to mark all traffic coming from groupname iptables -t mangle -A OUTPUT -m owner --gid-owner groupname -j MARK --set-mark 42 Afterwards we tell iptables to to some SNAT and tell ip route to use special routing table for marked traffic packets. Problem: if the VPN failes, there is a chance that the special to-be-tunneled program communicates over the normal eth0 interface. Desired solution: All marked traffic should not be allowed to go directly through eth0, it has to go through tun0 first. I tried the following commands which didn't work: iptables -A OUTPUT -m owner --gid-owner groupname ! -o tun0 -j REJECT iptables -A OUTPUT -m owner --gid-owner groupname -o eth0 -j REJECT It might be the problem, that the above iptable-rules didn't work due to the fact, that the packets are first marked, then put into tun0 and then transmitted by eth0 while they are still marked.. I don't know how to de-mark them after in tun0 or to tell iptables, that all marked packet may pass eth0, if they where in tun0 before or if they going to the gateway of my VPN provider. Does someone has any idea to a solution? Some config infos: iptables -nL -v --line-numbers -t mangle Chain OUTPUT (policy ACCEPT 11M packets, 9798M bytes) num pkts bytes target prot opt in out source destination 1 591K 50M MARK all -- * * 0.0.0.0/0 0.0.0.0/0 owner GID match 1005 MARK set 0x2a 2 82812 6938K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 owner GID match 1005 CONNMARK save iptables -nL -v --line-numbers -t nat Chain POSTROUTING (policy ACCEPT 393 packets, 23908 bytes) num pkts bytes target prot opt in out source destination 1 15 1052 SNAT all -- * tun0 0.0.0.0/0 0.0.0.0/0 mark match 0x2a to:VPN_IP ip rule add from all fwmark 42 lookup 42 ip route show table 42 default via VPN_IP dev tun0

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• Redirection of outbound UDP port NTP.

  - by pboin

  For my residential service, I changed ISPs to Zoom/Armstrong. Just after that, my NTP daemons stopped working. I dug deep and diagnosed the problem: Unprivileged ports are getting out. When i run 'ntpdate' for example, I go out on a high, unprivleged port, and get a response on UDP 123. That's fine. The 'ntpd' daemon though, expects to go out on 123 and get its reply there as well. This must be a common problem, because it's directly addressed in the NTP troubleshooting guide. Just to see what would happen, I wrote a detailed email to the general support address at Armstrong. They replied almost immediately with a complete technical answer! They have everything <1024 blocked, except for a few ports to support outbound VPN. So, the question: Can I use IPtables to essentially re-write my outbound UDP 123 up to 2123 or something like that? If I do, does there need to be a corresponding 2123-123 rule to translate the reply? This seems like NAT, but with ports, not addresses. True, I could run ntpdate from cron, but that loses all of the adjustment smarts of NTP.

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• Road Warrior VPN Setup

  - by wobblycogs

  I apologise up front for the rather open ended nature of this question but I've got well out of my depth and could really do with some pointers. I need to set up a road warrior VPN solution which will allow our customers to securely access a number of services we provide for them. Customer machines will be running a variety of Windows versions from XP onwards with a variety of patch levels. Typically they will connect from the clients main offices but not always. It is safe to assume that all clients will be behind NATs but we may occasionally see a connection that isn't NAT'ed. Typical connection situation is therefore: Customer Laptop -- Router (NAT) -- Internet -- VPN Server + Firewall -- Server (Win 2008 R2, Non-routable IP) There will initially be a dozen or so people that could connect but that will grow quickly to around 100. It's unlikely that we'll see that many concurrent connections though, I imagine our total VPN throughput would be <50Mbps peak. What are my options for setting this up? I've been trying to set up a system like this using a MikroTik router for a few days but have struggled to get it working correctly, particularly with NAT'ed clients. I've had a quick look at OpenVPN and liked what I saw but I think it's unlikely our customers IT departments would allow the client to be installed. Finally I've looked at the Cisco ASA range but I'm on a fairly tight budget so this is less preferable but it looks like it would work pretty much out of the box. My fall back position is to connect the server directly and use the provided VPN + Firewall facilities but that is far from ideal as the number of servers is likely to grow over time.

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• CLOSE_WAIT sockets burst - perhaps because of iptables settings?

  - by Fabrizio Giudici

  I have an Ubuntu 12.04 server virtual box where basically the installed software and configuration are the default ones, plus the installation of a jetty 6 server which servers a few websites. To keep things simple I didn't install apache httpd and used iptables for exposing jetty (which runs on the 8080 port) to the port 80. These are the results of /sbin/iptables -t nat -L Chain PREROUTING (policy ACCEPT) target prot opt source destination REDIRECT tcp -- anywhere localhost tcp dpt:http redir ports 8080 REDIRECT tcp -- anywhere Ubuntu-1104-natty-64-minimal tcp dpt:http redir ports 8080 Chain INPUT (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination REDIRECT tcp -- anywhere localhost tcp dpt:http redir ports 8080 REDIRECT tcp -- anywhere Ubuntu-1104-natty-64-minimal tcp dpt:http redir ports 8080 Chain POSTROUTING (policy ACCEPT) target prot opt source destination I must confess I have a shallow comprehension of how iptables works, in particular for the different kind of chains. This thing works, but sometimes I have an explosion of sockets that stay permanently in CLOSE_WAIT state. I know about what this state means, but since I didn't write the code that manages servlets (they are handled by jetty) I can't fix the problem by patching my code. Eventually the amount of CLOSE_WAIT sockets builds up and makes the server not responsive, so I have to restart jetty. I've looked around for similar problems wth CLOSE_WAIT, and only found cases related to the programmer's code, or problems with Tomcat, not Jetty. I was wondering whether they could be related to a partially broken iptables configuration (the alternative is a bug in Jetty 6, but I first want to exclude other possible causes). Thanks.

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