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  • Determine the time difference between two linux servers

    - by Paul
    I am troubleshooting a latency network issue on a network. It is probably a nic or cabling issue, but while I was going through the process of figuring it out, I was looking at the timings of a ping packet leaving a network card and arriving at another server. Both linux. So I have tcpdump running on both, and I issue a ping from one to the other, and back again, and looking at the timing differences might have shed light on where the latency is coming from. It is an academic exercise now, as I need to eliminate some more fundamental causes, but I was curious as to how this could be achieved. Given that ntpd is installed and running on two servers, how can I confirm the current time discrepency between the two servers, to whatever level of accuracy is possible - given that we are talking about latency on a local lan, which is ideally a millisecond or so. NTP itself is accurate to a couple of ms under good conditions, and as both servers are in the same environment, they should (presumably) achieve a similar level of accuracy, and so should have a time discrepency between them of a only few ms - but how can I check this?

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  • Windows Server 2008 R2 install reboots unexpectedly during "Completing installation" phase

    - by knda
    I am attempting to install Windows Server 2008 R2 onto a Cisco UCS C201 M2 rack mounted server but am having major difficulties and wondering if anyone has some insight or items they could recommend for me to look at to get this one resolved. Installation is being attempted via the Cisco remote console (using CIMC's Virtual dvd-rom).. following the first phase of Setup where the installation files are copied to the target hard drive, then a reboot occurs to load Setup from the HDD, mid-way in the "Completing Installation" phase the system then reboots unexpectedly. System configuration Cisco UCS C201 M2 (2RU rack mounted server) 16GB RAM, 2x 73GB 15K SAS, 4x 300GB 10k SAS Add-on cards - Intel quad-port GigE card (no fibre channel cards) Storage - LSI MegaRAID SAS 9261-8i. onboard SATA is disabled (no SATA drives connected) KVM - Belkin No physical DVD-ROM.. :( I have... Run memtest86+, no RAM faults Disabled/enabled SATA support (BIOS) Attempted install from USB DVD-ROM, no effect Attempted unattended install scripted via Cisco Configuration Manager DVD provided Removed Belkin KVM in case that was causing drama Discovered that the Cisco website is "awesome" for searching for PDFs/Drivers cough, reverted back to Google Downloaded latest LSI drivers from LSI's site and used during Server 2008 install checked Windows ISO against checksum's from MS site checked Windows ISO by using it for an install in a VM Running out of ways to troubleshoot this as I am not sure how to enable any sort of 'verbose' mode during the setup process. Next step I have planned is to remove the Intel NIC and try the installation again.. Edit: Problem was the "Cisco INTEL QUAD PT GBE" (1000/PT) .. will have to see if this card is faulty or if it's just drivers.. thanks for the help.

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  • Cisco Multi-DMZ firewall

    - by BParker
    I need to find a firewall that will give me 1 LAN port, and 5-7 DMZ ports. I have a requirement to replace some FreeBSD systems that are used to run some testing equipment. It is essential that the DMZ ports cannot communicate with each other, but the LAN port can communicate with everyone. That way a user on the LAN can connect to the test systems, but the test systems are isolated entirely and cannot interfere with each other. One of the DMZ's will be connected to a VMWare ESXi server, one to a standard server, and the rest to various types of equipment. The lan port will be connected to the corporate LAN switch. Sorry if i am a little vague, I am just trying to work all this out myself! Currently we have a FreeBSD configured, but the quad port NIC's are pretty expensive, and the PC itself is old, so i would prefer to replace it with a dedicate piece of kit which can do the same job, but more reliably! These test rigs are used all over the place, and get moved quite often, so i am aiming for Cisco kit for ease of configuration and reliability of the hardware itself. Thanks

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  • Split Tunnel VPN using incorrect Tunnel

    - by Brian Schmeltz
    Our company has a handful of field offices that have recently been setup with a regular internet connection after we removed the T1 and router that connected them directly to our network. Now, when the users are in the office, they log in to the VPN to be able to connect to the network. For the sake of them being able to print and scan from the local multi-function we have setup a split tunnel VPN. We currently have about 15-20 users using this setup around the country without any problems. Recently one of our users started having problems accessing internal programs/sites when connecting from both home and the office. There are three other users in the same office and they do not have this problem. I assumed that it was something with the computer and went ahead and replaced it with another of the same model. The computer worked fine in our home office; however, when the user received it, she had the exact same problem both at home and in the field office. Thinking it may be a NIC driver issue I sent her another computer, this time a different model, same problem occurred. If I update the host file to point to the correct paths, things will work, and if I connect via a normal VPN connection everything works, but the user cannot scan or print - which is a problem. Have tried to find ways to create another tunnel on a normal VPN and have tried to find ways to force the correct tunnel on the split tunnel VPN. It appears that there is something related to the ISP because if I connect to Comcast or Verizon it is fine but once she connects to Insite then she has problems. I have been unable to get any support from Insite as they don't feel the issue is with them. We use a Nortel VPN client. Any thoughts or ideas would be appreciated.

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  • Debian/OVH: How to configure multiple Failover IP on the same Xen (Debian) Virtual Machine?

    - by D.S.
    I have a problem on a Xen virtual machine (running latest Debian), when I try to configure a second failover IP address. OVH reports that my IP is misconfigured and they complaint they receive a massive quantity of ARP packets from this IPs, so they are going to block my IP unless I fix this issue. I suspect there's a routing issue, but I don't know (and can't find any useful info on the provider's website, and their support doesn't provide me a valid solution, just bounce me to their online - useless - guides). My /etc/network/interfaces look like this: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address AAA.AAA.AAA.AAA netmask 255.255.255.255 broadcast AAA.AAA.AAA.AAA post-up route add 000.000.000.254 dev eth0 post-up route add default default gw 000.000.000.254 dev eth0 # Secondary NIC auto eth0:0 iface eth0:0 inet static address BBB.BBB.BBB.BBB netmask 255.255.255.255 broadcast BBB.BBB.BBB.BBB And the routing table is: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 000.000.000.254 0.0.0.0 255.255.255.255 UH 0 0 0 eth0 0.0.0.0 000.000.000.254 0.0.0.0 UG 0 0 0 eth0 In these examples (true IP addresses are replaced by fake ones, guess why :)), 000.000.000.000 is my main server's IP address (dom0), 000.000.000.254 is the default gateway OVH recommends, AAA.AAA.AAA.AAA is the first IP Failover and BBB.BBB.BBB.BBB is the second one. I need both AAA.AAA.AAA.AAA and BBB.BBB.BBB.BBB to be publicly reachable from Internet and point to my domU, and to be able to access Internet from inside the virtual machine (domU). I am using eth0 and eth0:0 because due to OVH support, I have to assign both IPs to the same MAC address and then create a virtual eth0:0 interface for the second IP. Any suggestion? What am I doing wrong? How can I stop OVH complaining about ARP flood? Many thanks in advance, DS

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  • Hyper-V Virtual Machine Networking issues related to Max Ethernet Frame Size

    - by Goatmale
    I fixed an issue today earlier today but i'm interested in learning WHY it worked. We set up a new Hyper-V virtual machine only to discover that HTTP traffic wasn't working. HTTPS, pings, everything else was working fine. After months of prodding around I took a shot in the dark. On the Hyper-V host server, the physical NIC card had an advanced setting of "Max Ethernet Frame Size" set to 1500. After setting this setting to 1514 the issue was fixed. Alternatively, setting this to 1512 did not solve the issue; 1514 is the magic number. My best guess it that when this setting was set to 1500 it was allowing incoming pings because the data payload was a lot smaller of say, HTTP traffic. As far as HTTPS traffic, I read about something called "Path MTU discovery" which i'm going to assume why is HTTPs traffic was getting through fine, albeit slower. Looking at this post, people agree that 1518 is the max total frame size. Why didn't I need to change this to 1518 instead of 1514 bytes? Why is the default frame size 1500 if that's the max size of the Ethernet payload and not the max size.

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  • hadoop: port appears open locally but not remotelly

    - by miguel
    I am new to linux and hadoop and I am having the same issue as in this question. I think I understand what is causing it but I don't know how to solve it (Don't know what they mean by "Edit the Hadoop server's configuration file so that it includes its NIC's address."). The other post that they link says that the configuration files should refer to the machine's externally accessible host name. I think I got this right as every hadoop configuration file refers to "master" and the etc/hosts file lists the master by its private IP address. How can I solve this? Edit: I have 5 nodes: master, slavec, slaved, slavee and slavef all running debian. This is the hosts file in master: 127.0.0.1 master 10.0.1.201 slavec 10.0.1.202 slaved 10.0.1.203 slavee 10.0.1.204 slavef this is the hosts file in slavec (it looks similar in the other slaves): 10.0.1.200 master 127.0.0.1 slavec 10.0.1.202 slaved 10.0.1.203 slavee 10.0.1.204 slavef the masters file in master: master the slaves file in master: master slavec slaved slavee slavef the masters and slaves file in slavex has only one line: slavex

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  • KVM guest VLAN aware problems

    - by baraka
    Hi, We are using Centos 5.5. as KVM host. It has two nics. One for management and the other one for services. As we have services in multiple vlans this nic is configured as a 802.1Q trunk. Any VM must be able to have access to any vlan, so host trunk interface is bridged to its tap interface and vlan is configured inside VM. Everything works fine while there is not heavy traffic. I can not find any log on guest or host, but, after some certain sustained big file transfer (about 6Gb) bridging stop working. Other guest on the same host continue working without problems. tcpdump on bridge interface is Ok, but on guest tap inferface I can see only outgoing traffic. Restarting bridge or rejoining tap interface doesn't provide any clue. Rebooting guest turns on bridge again. Bridge configuration is minimal: just addbr and addif (no stp). Any idea welcome!

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  • Split Tunnel VPN using incorrect Tunnel

    - by Brian Schmeltz
    Our company has a handful of field offices that have recently been setup with a regular internet connection after we removed the T1 and router that connected them directly to our network. Now, when the users are in the office, they log in to the VPN to be able to connect to the network. For the sake of them being able to print and scan from the local multi-function we have setup a split tunnel VPN. We currently have about 15-20 users using this setup around the country without any problems. Recently one of our users started having problems accessing internal programs/sites when connecting from both home and the office. There are three other users in the same office and they do not have this problem. I assumed that it was something with the computer and went ahead and replaced it with another of the same model. The computer worked fine in our home office; however, when the user received it, she had the exact same problem both at home and in the field office. Thinking it may be a NIC driver issue I sent her another computer, this time a different model, same problem occurred. If I update the host file to point to the correct paths, things will work, and if I connect via a normal VPN connection everything works, but the user cannot scan or print - which is a problem. Have tried to find ways to create another tunnel on a normal VPN and have tried to find ways to force the correct tunnel on the split tunnel VPN. It appears that there is something related to the ISP because if I connect to Comcast or Verizon it is fine but once she connects to Insite then she has problems. I have been unable to get any support from Insite as they don't feel the issue is with them. We use a Nortel VPN client. Any thoughts or ideas would be appreciated.

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  • OpenVPN Client timing out

    - by Austin
    I recently installed OpenVPN on my Ubuntu VPS. Whenenver I try to connect to it, I can establish a connection just fine. However, everything I try to connect to times out. If I try to ping something, it will resolve the IP, but will time out after resolving the IP. (So DNS Server seems to be working correctly) My server.conf has this relevant information (At least I think it's relevant. I'm not sure if you need more or not) # Which local IP address should OpenVPN # listen on? (optional) ;local a.b.c.d # Which TCP/UDP port should OpenVPN listen on? # If you want to run multiple OpenVPN instances # on the same machine, use a different port # number for each one. You will need to # open up this port on your firewall. port 1194 # TCP or UDP server? ;proto tcp proto udp # "dev tun" will create a routed IP tunnel, # "dev tap" will create an ethernet tunnel. # Use "dev tap0" if you are ethernet bridging # and have precreated a tap0 virtual interface # and bridged it with your ethernet interface. # If you want to control access policies # over the VPN, you must create firewall # rules for the the TUN/TAP interface. # On non-Windows systems, you can give # an explicit unit number, such as tun0. # On Windows, use "dev-node" for this. # On most systems, the VPN will not function # unless you partially or fully disable # the firewall for the TUN/TAP interface. ;dev tap dev tun # Windows needs the TAP-Win32 adapter name # from the Network Connections panel if you # have more than one. On XP SP2 or higher, # you may need to selectively disable the # Windows firewall for the TAP adapter. # Non-Windows systems usually don't need this. ;dev-node MyTap # SSL/TLS root certificate (ca), certificate # (cert), and private key (key). Each client # and the server must have their own cert and # key file. The server and all clients will # use the same ca file. # # See the "easy-rsa" directory for a series # of scripts for generating RSA certificates # and private keys. Remember to use # a unique Common Name for the server # and each of the client certificates. # # Any X509 key management system can be used. # OpenVPN can also use a PKCS #12 formatted key file # (see "pkcs12" directive in man page). ca ca.crt cert server.crt key server.key # This file should be kept secret # Diffie hellman parameters. # Generate your own with: # openssl dhparam -out dh1024.pem 1024 # Substitute 2048 for 1024 if you are using # 2048 bit keys. dh dh1024.pem # Configure server mode and supply a VPN subnet # for OpenVPN to draw client addresses from. # The server will take 10.8.0.1 for itself, # the rest will be made available to clients. # Each client will be able to reach the server # on 10.8.0.1. Comment this line out if you are # ethernet bridging. See the man page for more info. server 10.8.0.0 255.255.255.0 # Maintain a record of client <-> virtual IP address # associations in this file. If OpenVPN goes down or # is restarted, reconnecting clients can be assigned # the same virtual IP address from the pool that was # previously assigned. ifconfig-pool-persist ipp.txt # Configure server mode for ethernet bridging. # You must first use your OS's bridging capability # to bridge the TAP interface with the ethernet # NIC interface. Then you must manually set the # IP/netmask on the bridge interface, here we # assume 10.8.0.4/255.255.255.0. Finally we # must set aside an IP range in this subnet # (start=10.8.0.50 end=10.8.0.100) to allocate # to connecting clients. Leave this line commented # out unless you are ethernet bridging. ;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100 # Configure server mode for ethernet bridging # using a DHCP-proxy, where clients talk # to the OpenVPN server-side DHCP server # to receive their IP address allocation # and DNS server addresses. You must first use # your OS's bridging capability to bridge the TAP # interface with the ethernet NIC interface. # Note: this mode only works on clients (such as # Windows), where the client-side TAP adapter is # bound to a DHCP client. ;server-bridge # Push routes to the client to allow it # to reach other private subnets behind # the server. Remember that these # private subnets will also need # to know to route the OpenVPN client # address pool (10.8.0.0/255.255.255.0) # back to the OpenVPN server. ;push "route 192.168.10.0 255.255.255.0" ;push "route 192.168.20.0 255.255.255.0" # To assign specific IP addresses to specific # clients or if a connecting client has a private # subnet behind it that should also have VPN access, # use the subdirectory "ccd" for client-specific # configuration files (see man page for more info). # EXAMPLE: Suppose the client # having the certificate common name "Thelonious" # also has a small subnet behind his connecting # machine, such as 192.168.40.128/255.255.255.248. # First, uncomment out these lines: ;client-config-dir ccd ;route 192.168.40.128 255.255.255.248 # Then create a file ccd/Thelonious with this line: # iroute 192.168.40.128 255.255.255.248 # This will allow Thelonious' private subnet to # access the VPN. This example will only work # if you are routing, not bridging, i.e. you are # using "dev tun" and "server" directives. # EXAMPLE: Suppose you want to give # Thelonious a fixed VPN IP address of 10.9.0.1. # First uncomment out these lines: ;client-config-dir ccd ;route 10.9.0.0 255.255.255.252 # Then add this line to ccd/Thelonious: # ifconfig-push 10.9.0.1 10.9.0.2 # Suppose that you want to enable different # firewall access policies for different groups # of clients. There are two methods: # (1) Run multiple OpenVPN daemons, one for each # group, and firewall the TUN/TAP interface # for each group/daemon appropriately. # (2) (Advanced) Create a script to dynamically # modify the firewall in response to access # from different clients. See man # page for more info on learn-address script. ;learn-address ./script # If enabled, this directive will configure # all clients to redirect their default # network gateway through the VPN, causing # all IP traffic such as web browsing and # and DNS lookups to go through the VPN # (The OpenVPN server machine may need to NAT # or bridge the TUN/TAP interface to the internet # in order for this to work properly). push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 8.8.8.8" # Certain Windows-specific network settings # can be pushed to clients, such as DNS # or WINS server addresses. CAVEAT: # http://openvpn.net/faq.html#dhcpcaveats # The addresses below refer to the public # DNS servers provided by opendns.com. ;push "dhcp-option DNS 8.8.8.8" push "dhcp-option DNS 8.8.4.4" # Uncomment this directive to allow different # clients to be able to "see" each other. # By default, clients will only see the server. # To force clients to only see the server, you # will also need to appropriately firewall the # server's TUN/TAP interface. ;client-to-client # Uncomment this directive if multiple clients # might connect with the same certificate/key # files or common names. This is recommended # only for testing purposes. For production use, # each client should have its own certificate/key # pair. # # IF YOU HAVE NOT GENERATED INDIVIDUAL # CERTIFICATE/KEY PAIRS FOR EACH CLIENT, # EACH HAVING ITS OWN UNIQUE "COMMON NAME", # UNCOMMENT THIS LINE OUT. ;duplicate-cn # The keepalive directive causes ping-like # messages to be sent back and forth over # the link so that each side knows when # the other side has gone down. # Ping every 10 seconds, assume that remote # peer is down if no ping received during # a 120 second time period. keepalive 10 120 # For extra security beyond that provided # by SSL/TLS, create an "HMAC firewall" # to help block DoS attacks and UDP port flooding. # # Generate with: # openvpn --genkey --secret ta.key # # The server and each client must have # a copy of this key. # The second parameter should be '0' # on the server and '1' on the clients. ;tls-auth ta.key 0 # This file is secret # Select a cryptographic cipher. # This config item must be copied to # the client config file as well. ;cipher BF-CBC # Blowfish (default) ;cipher AES-128-CBC # AES ;cipher DES-EDE3-CBC # Triple-DES # Enable compression on the VPN link. # If you enable it here, you must also # enable it in the client config file. comp-lzo # The maximum number of concurrently connected # clients we want to allow. ;max-clients 100 # It's a good idea to reduce the OpenVPN # daemon's privileges after initialization. # # You can uncomment this out on # non-Windows systems. ;user nobody ;group nogroup # The persist options will try to avoid # accessing certain resources on restart # that may no longer be accessible because # of the privilege downgrade. persist-key persist-tun # Output a short status file showing # current connections, truncated # and rewritten every minute. status openvpn-status.log # By default, log messages will go to the syslog (or # on Windows, if running as a service, they will go to # the "\Program Files\OpenVPN\log" directory). # Use log or log-append to override this default. # "log" will truncate the log file on OpenVPN startup, # while "log-append" will append to it. Use one # or the other (but not both). ;log openvpn.log ;log-append openvpn.log # Set the appropriate level of log # file verbosity. # # 0 is silent, except for fatal errors # 4 is reasonable for general usage # 5 and 6 can help to debug connection problems # 9 is extremely verbose verb 3 # Silence repeating messages. At most 20 # sequential messages of the same message # category will be output to the log. ;mute 20 I've tried on multiple computers by the way. The same result on all of them. What could be wrong? Thanks in advance, and if you need other information I'll gladly post it. Information for new comments root@vps:~# iptables -L -n -v Chain INPUT (policy ACCEPT 862K packets, 51M bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 3 packets, 382 bytes) pkts bytes target prot opt in out source destination 0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 4641 298K ACCEPT all -- * * 10.8.0.0/24 0.0.0.0/0 0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable Chain OUTPUT (policy ACCEPT 1671K packets, 2378M bytes) pkts bytes target prot opt in out source destination And root@vps:~# iptables -t nat -L -n -v Chain PREROUTING (policy ACCEPT 17937 packets, 2013K bytes) pkts bytes target prot opt in out source destination Chain POSTROUTING (policy ACCEPT 8975 packets, 562K bytes) pkts bytes target prot opt in out source destination 1579 103K SNAT all -- * * 10.8.0.0/24 0.0.0.0/0 to:SERVERIP Chain OUTPUT (policy ACCEPT 8972 packets, 562K bytes) pkts bytes target prot opt in out source destination

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  • Internet doesn't work when enable local network

    - by rakesh yadav
    We have the following network setup: A) Router IP 192.168.51.49 B) Windows Server 2008 R2 with dual NIC: Lan A) WAN interface (192.168.51.50) ( Used for internet) Lan B) LAN interface (192.168.30.228) ( used for local connectivity ) When I keep both LAN Enabled than my internet doesn't work, but if I disable my local LAN then internet works fine. How can I resolve this issue? Do I need to do routing on my server Please find the below attached route print result C:\Users\Administrator>route print =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.51.49 192.168.51.50 276 0.0.0.0 0.0.0.0 192.168.30.227 192.168.30.228 266 192.168.30.224 255.255.255.240 On-link 192.168.30.228 266 192.168.30.228 255.255.255.255 On-link 192.168.30.228 266 192.168.30.239 255.255.255.255 On-link 192.168.30.228 266 192.168.51.48 255.255.255.240 On-link 192.168.51.50 276 192.168.51.50 255.255.255.255 On-link 192.168.51.50 276 192.168.51.63 255.255.255.255 On-link 192.168.51.50 276 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 202.56.230.5 255.255.255.255 192.168.51.49 192.168.51.50 21 202.56.230.6 255.255.255.255 192.168.51.49 192.168.51.50 21 192.168.26.124 255.255.255.255 192.168.51.49 192.168.51.50 21 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 192.168.51.50 276 224.0.0.0 240.0.0.0 On-link 192.168.30.228 266 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 192.168.51.50 276 255.255.255.255 255.255.255.255 On-link 192.168.30.228 266 =========================================================================== Persistent Routes: Network Address Netmask Gateway Address Metric 0.0.0.0 0.0.0.0 192.168.30.227 Default 0.0.0.0 0.0.0.0 192.168.51.49 Default ===========================================================================

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  • Windows 7 network performance tuning for LAN

    - by Hubert Kario
    I want to tune Windows 7 TCP stack for speed in a LAN environment. Bit of background info: I've got a Citrix XenServer set up with Windows 2008R2, Windows 7 and Debian Lenny with Citrix kernel, Windows machines have Tools installed the iperf server process is running on different host, also Debian Lenny. The servers are otherwise idle, tests were repeated few times to confirm results. While testing with iperf 2008R2 can achieve around 600-700Mbps with no tuning what so ever but I can't find any guide or set of parameters that will make Windows 7 achieve anything over 150Mbps with no change in TCP window size using -w parameter to iperf. I tried using netsh autotuining to disabled, experimental, normal and highlyrestricted - no change. Changing congestionprovider doesn't do anything, just as rss and chimney. Setting all the available settings to same values as on Windows 2008R2 host doesn't help. To summarize: Windows 2008R2 default settings: 600-700Mbps Debian, default settings: 600Mbps Windows 7 default settings: 120Mbps Windows 7 default, iperf -w 65536: 400-500Mbps While the missing 400Mbps in performance I blame on crappy Realtek NIC in the XenServer host (I can do ~980Mbps from my laptop to the iperf server) it doesn't explain why Windows 7 can't achieve good performance without manually tuning window size at the application level. So, how to tune Windows 7?

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  • How to get gigabit network speeds on Windows XP?

    - by JB
    We've just installed gigabit switches at work, and things on the Linux side are going well. Our linux boxes, which use a Intel Corporation 82566DM-2 Gigabit nic (according to lspci), consistently get over 900 mbits/sec: iperf -c ipserver ------------------------------------------------------------ Client connecting to ipserver, TCP port 5001 TCP window size: 16.0 KByte (default) ------------------------------------------------------------ [ 3] local 192.168.40.9 port 39823 connected with 192.168.1.115 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.08 GBytes 929 Mbits/sec We have a bunch of Windows XP 64-bit machines that use Broadcom NetXtreme 57xx cards. I spent around a day trying to get equivalent speeds on them, but couldn't get above 200 Mbits/sec. I noticed the Windows iperf tests said that the TCP window size was 8 Kb by default (as opposed to 16 Kb on Linux, so I modified my test to reflect that. Still no love. I went to Broadcom's site, downloaded the latest drivers for the card and installed. Still no love. However, finally, I tried a 64 Kb window size with the new drivers, and finally an improvement! $ iperf -c ipserver -w64k ------------------------------------------------------------ Client connecting to ipserver, TCP port 5001 TCP window size: 64.0 KByte ------------------------------------------------------------ [ 3] local 192.168.40.214 port 1848 connected with 192.168.1.115 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 933 MBytes 782 Mbits/sec Much better, but still not really taking advantage of the full capabilities of the network. If the Linux box can reach 950 Mbits/sec consistently, this box should be able to as well. Also, if you're wondering about the medium, this is over the same cable...I'm switching back and forth. Any suggestion or ideas would be really welcome. Thanks!

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  • Very slow browsing shared folder XP client/host

    - by Ickster
    I have a pretty straightforward setup where I'm storing media files on an XP pro machine, and sharing the folder to be accessed by other XP pro machines around the house. (Typically, there's only one client accessing the share at a time, although there may be several with the share mounted.) It's been working just fine for years, but I've recently started having some problems. A couple of days ago, the host PC had power disconnected while it was running. It was restarted and everything seemed fine initially, but since then browsing the shared folder from client machines has been extremely slow and actually reading data is all but impossible. The problem exists in every access method I've tried: Windows Explorer, VLC dialogs, command line, etc. My first thought was that the disk was experiencing problems, but there are no problems viewing the files locally on the host machine. My second thought was that there was a network problem on the host machine, so I removed and reinstalled drivers for the NIC with no change. My third thought was that there might've been a problem elsewhere on the network, so I swapped out hardware to no avail. I'm regrouping and trying to come up with a methodical approach to figuring out what might be wrong. I would of course be thrilled if you can suggest specific problems (Microsoft KB articles, etc.) that I might check, but I'm not expecting a silver bullet. If you can help me outline an approach to identify the problem (including recommended tools, e.g., disk checkers, network analyzers, etc.) I'd greatly appreciate it.

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  • VMWare Guest Info - Wrong IP Returned

    - by Jon Bailey
    We're running a VDI environment with vSphere 4.0 and Oracle VDI 3.2.2 and are having a bit of a problem with users that connect to an IPSec VPN from within their VM. For some reason, once connected to the VPN, the VMWare API returns GuestInfo.ipAddress as the VPN IP rather than the primary IP of the only NIC on the system. The IP address shown in net[0].ipAddress is the correct address and is what vSphere client is reporting. Is there any way to get VMWare tools to report the net[0].ipAddress as GuestInfo.ipAddress? Below is sample output from the guestinfo.pl script. 172.16.1.2 is the example "bad" VPN address that our VDI software is seeing. VMXFLEX01 guestFamily: windowsGuest VMXFLEX01 guestFullName: Microsoft Windows XP Professional (32-bit) VMXFLEX01 guestId: winXPProGuest VMXFLEX01 guestState: running VMXFLEX01 hostName: VMXFLEX01 VMXFLEX01 ipAddress: 172.16.1.2 VMXFLEX01 toolsStatus: VMware Tools is running and the version is current. VMXFLEX01 toolsVersion: 8194 VMXFLEX01 Screen - Height: 600 VMXFLEX01 Screen - Width: 800 VMXFLEX01 Disk[0]: Capacity 42935926784 VMXFLEX01 Disk[0]: Path : C:\ VMXFLEX01 Disk[0]: freespace : 33272619008 VMXFLEX01 net[0] - connected : 1 VMXFLEX01 net[0] - deviceConfigId : 4000 VMXFLEX01 net[0] - macAddress : 00:50:56:95:1f:c9 VMXFLEX01 net[0] - network : VM Network VMXFLEX01 net[0] - ipAddress : 10.0.0.2

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  • Bad network performance on KVM guest

    - by Devator
    I have a dedicated server connected to a 1000 Mbit port. However, the Debian guest is only getting half to a 1/4 the speeds: On the node itself (Linux node 2.6.32-279.9.1.el6.x86_64 #1 SMP Tue Sep 25 21:43:11 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux): wget http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin -O /dev/null --2012-11-11 23:10:11-- http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin Resolving www.bbned.nl... 62.177.144.181 Connecting to www.bbned.nl|62.177.144.181|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 1048576000 (1000M) [application/octet-stream] Saving to: â/dev/nullâ 100%[====================================>] 1,048,576,000 100M/s in 10s 2012-11-11 23:10:21 (100 MB/s) - â/dev/nullâ On the guest (Debian 6.0.5, x64: Linux debian 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux): wget http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin -O /dev/null --2012-11-11 23:10:41-- http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin Resolving www.bbned.nl... 62.177.144.181 Connecting to www.bbned.nl|62.177.144.181|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 1048576000 (1000M) [application/octet-stream] Saving to: â/dev/nullâ 100%[=================================================================================================================================================================================================>] 1,048,576,000 16.5M/s in 42s 2012-11-11 23:11:23 (23.8 MB/s) - â/dev/nullâ I use the virtio NIC. I tried some more NICs: e1000 and the Realtek 8139 but those yield even worse results. Anyone has an idea how to improve these speeds?

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  • RRAS Public Address Pool on Windows Server 2008

    - by Art
    I have a Windows 2008 server with two NICs running RRAS and a small public website. It also does NAT for several other PCs on my network and everything works great. I have a block of 5 public static IPs from my ISP, one of which is bound to the public NIC in the Windows 2008 server. I would like to assign one of the remainging 4 public IPs to a machine on my private network. I thought I could do this by going into RRAS, selecting NAT under IPv4 and then adding the public IP address to the address pool and specifying a reservation for the machine I would like to use that address by adding its private ip address. When I do this, the machine I reserved the public IP address for seems to loose all outside network connectivity. I can still ping other PCs on my 192.168.0.* net, but anything outside is no longer reachable. When I remove the reservation, everything seems to work. After setting the reservation and right clicking on the external public interface and selecting 'Show Mappings' I can see outbound requests from my private address with the desired associated private address, however I do not see any inbound requests. What am I doing wrong/missing?

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  • vDS - vCenter Problem

    - by rbmadison
    We are implementing a vSphere farm and are using a distrubuted switch. The VC is a VM within the farm connected to the distrubuted switch. We had a SAN issue and all of our VMs were down. When the SAN recovered and we restarted the ESX host containing the VC the VC couldn't connect to the network through the vDS. We had to remove a NIC from the vDS on that host and create a regular vswitch and then connect the VC to that before the VC would connect to the network. Is this typical behavior? If the VC goes down does all vDS networking stop on all the hosts? That seems to be a very bad thing. I thought networking would work even though the VC is down because the hosts have the vDS configuration cached. Is there a better way to configure it to prevent this from happening. We want to keep the VC as a VM for HA and recoverabilty purposes. Can anyone offer suggestions or explanations? I appreciate the help. Thanks, Rick

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  • how does a computer know which IP address will route information to the internet? [closed]

    - by JohnMerlino
    Possible Duplicate: How does IPv4 Subnetting Work? For example, I have a computer with a Network Inteface Card (NIC) which is an Ethernet card that is connected by Ethernet cables to a router. There is also another computer with a cable that is connected in another port of the router. This is a Belkin router operating over an Ethernet in the LAN. When I connect to serverfault.com, it maps to an IP address. My computer now has a task of connecting to that IP address. But my computer itself cannot connect to the serverfault IP address. Only the router can. So the task of my computer is to find the IP address associated with the node that will do the routing to the public internet. How does my computer know that a particular IP address in the local network belongs to the router, and is not another computer connected to the network? Is this information configured manually in the operating system itself? Somehow my computer must know that it must send ethernet frames to the router with the expectation that the router will then send the packet to a public IP. How does it know to send it to the router? Is the router's ip address stored in my computer like a key/value pair e.g. "router"="192.168.2.6", so that when I put a public ip address, my computer first knows to connect to 192.168.2.6?

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  • How to remap IPs visible from local machine to IPs visible from a machine I have SSH access to?

    - by gooli
    I'm so far out of my depth I don't even know what to google for. There's a server I can connect to via SSH. Via that server I can access other server on its subnet via SSH. What I want to do is be able to access the machines that server has access to directly. Say the server IP is 192.168.7.7 and is the only one in the 192.168.x.x range I have access to. I'd like to configure things in such a way that when I to access say 192.168.7.100 on my machine, the connection will go through an SSH tunnel I open to 192.168.7.7 and out to 192.168.7.100. I would like this to work for any port if at all possible. I know I can set an HTTP proxy and even a SOCKS proxy, but I'm wondering is there is a way to actually remap some of the IP my machine sees to IP only visible from the remote machine. What would this configuration be called? IS this NAT, VPN, IP2IP or something else? How can I set up this on a Windows client box that connects via SSH to a Linux box? Sounds to me like I need to set up some kind of filtering on the network driver or possibly a virtual NIC, but I'm not sure where to go next.

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  • virtualisation with kvm: export services from guest to the host

    - by ascobol
    Hello, I would like to export some services from the guest os to the host os, via kvm, and by the same way learn some things about networking. I have tried the following commands: In the host (kubuntu 10.4): $ sudo tunctl -u ascobol Set 'tap0' persistent and owned by uid 2401 $ sudo ifconfig tap0 192.168.2.1 netmask 255.255.255.0 broadcast 192.168.2.255 The ifconfig command returns: $ /sbin/ifconfig tap0 Link encap:Ethernet HWaddr 3e:4e:e3:cc:bc:92 inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::3c4e:e3ff:fecc:bc92/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:17 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) $ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 tap0 Then I run the virtual machine (ubuntu server 10.4): $ sudo kvm -hda ubuntuserver104.qcow2 -net nic -net tap,name=tap0,script=no (I'm using sudo because without it fails with the following message:) warning: could not configure /dev/net/tun: no virtual network emulation With sudo the virtual machine boots, I just get this message: pci_add_option_rom: failed to find romfile "pxe-rtl8139.bin" In the virtual machine: $ ifconfig eth0 192.168.2.2 netmask 255.255.255.0 broadcast 192.168.2.255 Now if I run: $ ssh 192.168.2.2 I just get a No route to host What is wrong with this setup ? Thanks !

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  • How do I create a wifi network bridge with qemu on OS X?

    - by a paid nerd
    I grabbed a small FreeBSD live CD and QEMU, and I'm trying to bridge my Mac OS X 10.8 wifi connection so that the guest OS is available on my LAN. However, the guest OS never gets a DHCP lease. This works perfectly with VirtualBox in their "bridged" network mode, so I know it can be done. I need to get it working with QEMU because VirtualBox doesn't support the architecture that I need for this project. Here's what I've done so far based on hours of googling: Installed TUNTAP for OS X Told OS X to supposedly forward all packets, even ARP: (NOTE: This doesn't appear to work.) $ sudo sysctl -w net.inet.ip.forwarding=1 $ sudo sysctl -w net.link.ether.inet.proxyall=1 $ sudo sysctl -w net.inet.ip.fw.enable=1 Created a bridge: $ sudo ifconfig bridge0 create $ sudo ifconfig bridge0 addm en0 addm tap0 $ sudo ifconfig bridge0 up $ ifconfig bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 ether ac:de:xx:xx:xx:xx Configuration: priority 0 hellotime 0 fwddelay 0 maxage 0 ipfilter disabled flags 0x2 member: en0 flags=3<LEARNING,DISCOVER> port 4 priority 0 path cost 0 member: tap0 flags=3<LEARNING,DISCOVER> port 8 priority 0 path cost 0 tap0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500 ether ca:3d:xx:xx:xx:xx open (pid 88244) Started tcpdump with -I in the hopes that it enables promiscuous mode on the wifi device: $ sudo tcpdump -In -i en0 Run QEMU using the bridged network instructions: $ qemu-system-x86_64 -cdrom mfsbsd-9.2-RELEASE-amd64.iso -m 1024 \ -boot d -net nic -net tap,ifname=tap0,script=no,downscript=no But the guest system never gets a DHCP lease: If I tcpdump -ni tap0, I see lots of traffic from the wireless network. But if I tcpdump -ni en0, I don't see any DHCP traffic from the QEMU guest OS. Any ideas? Update 1: I tried sudo defaults write "/Library/Preferences/SystemConfiguration/com.apple.Boot" "Kernel Flags" "net.inet.ip.scopedroute=0" and rebooting per this mailing list suggestion, but this didn't help. In fact, it made VirtualBox bridged mode stop working.

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  • Internet doesn't work when enable local Lan

    - by rakesh yadav
    We have the following network setup: A) Router IP 192.168.51.49 B) Windows Server 2008 R2 with dual NIC: B1) WAN interface (192.168.0.2) ( Used for internet) B2) LAN interface (192.168.1.2) ( used for local connectivity) when i keep both LAN Enabled than my internet doesn't work, but if I disabled my local Lan than internet working fine. so please help me how can resolved this issue or should i need to do routing on my server Please find the below attached route print result C:\Users\Administrator>route print =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.51.49 192.168.51.50 276 0.0.0.0 0.0.0.0 192.168.30.227 192.168.30.228 266 192.168.30.224 255.255.255.240 On-link 192.168.30.228 266 192.168.30.228 255.255.255.255 On-link 192.168.30.228 266 192.168.30.239 255.255.255.255 On-link 192.168.30.228 266 192.168.51.48 255.255.255.240 On-link 192.168.51.50 276 192.168.51.50 255.255.255.255 On-link 192.168.51.50 276 192.168.51.63 255.255.255.255 On-link 192.168.51.50 276 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 202.56.230.5 255.255.255.255 192.168.51.49 192.168.51.50 21 202.56.230.6 255.255.255.255 192.168.51.49 192.168.51.50 21 192.168.26.124 255.255.255.255 192.168.51.49 192.168.51.50 21 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 192.168.51.50 276 224.0.0.0 240.0.0.0 On-link 192.168.30.228 266 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 192.168.51.50 276 255.255.255.255 255.255.255.255 On-link 192.168.30.228 266 =========================================================================== Persistent Routes: Network Address Netmask Gateway Address Metric 0.0.0.0 0.0.0.0 192.168.30.227 Default 0.0.0.0 0.0.0.0 192.168.51.49 Default ===========================================================================

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  • Troubleshooting loss of network connectivity in Windows 2003 - What else to check?

    - by Benny
    We are facing a weird problem in our data center. Our Backup server (running EMC Networker) loses network connection every alternate day around 3:00 AM (Backup schedule starts at midnight). After 2 hours of outage, the network connectivity recovers automatically and back to normal. What we observed: It is unlikely to be network issue, since it is directly connected to server farm switch (layer 2 connection without any intermediate hops). Further, the server is connected to two different switches for Load balancing using Broadcomm Teaming. a) If it were a switch related issue it is unlikely that both the network ports go down, since they are connected to different switch. b) A possibility Vlan wide issue is also ruled out since other devices in the same Vlan are fine. c) Switch interface status is always up. But there are lot of packet drops during the outage period - Can be attributed to high interface utilization of the backup server (near 100%) d) Connectivity is restored without any change on network. Next suspect is resource utilization on Windows server. Both CPU and Memory have rarely exceeded 80%, but NIC card utilization is alarmingly high (near 100%) Not really sure how to investigate this?

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  • Resolve another domain from current AD domain

    - by faulty
    We have 2 AD domain setup in our office. First is the primary domain for our office and exchange. The 2nd one is for development use to simulate production environment of our clients. Both domain are hosted on Windows 2008 R2 Enterprise. We, the development team has no access to the office domain other than login and email purpose. DNS is running on PDC of both domain. Both domain does not use public domain name. Now, our machines are joined to the development domain and we use outlook to access our office's exchange. We've added DNS entries for both the domain. From time to time we are having problem resolving our office domain (i.e. during outlook login), which we need to edit our NIC's DNS to have only DNS server from our office and then flush DNS. After that switch back once it's able to resolve. Is there a permanent solution for this scenario like specifying that the office domain be resolve with another DNS server when requested from the development domain? Thanks

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