** Package changed: ubuntu => network-manager (Ubuntu) ** Tags added: quantal
-- You received this bug notification because you are a member of Desktop Packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1110787 Title: VPN tunnel connections are not properly setting MTU values Status in “network-manager” package in Ubuntu: New Bug description: I regularly connect to a cisco anyconnect vpn using vpnc through the network manager. I am often at various different location using wifi, including connecting via wifi to a cellular hotspot. Usually, when connecting to a WIFI connection the MTU value (on the wifi connection) is 1500. When connecting to the vpn, the MTU value of the tun0 connection is set automatically and it usually sets itself to something like 1412. This works with no problem. When the wifi connection has a lower MTU value (and the cellular hotspot usually has an MTU of 1430, as do connections in various coffee shops), the tun0 connection still sets itself to 1412. For read-intensive operations (e.g. accessing websites and downloading pages, pulling from a subversion repository) there is no apparent problem. But when attempting to post to a web page (for instance, writing a bug report in bugzilla) or commit to a repository over the VPN, the connection will fail. The MTU value for a VPN connections seems to want to be 78 less than the MTU value of the connection that it is working over, and having MTU greater than this causes the upload failures. I use the VPN via the network manager (using network-manager-vpnc and network-manager-vpnc-gnome). I am able to work around the issue by setting the MTU value of the VPN connection manually from the command line after connecting with the following command: sudo ifconfig tun0 mtu 1330 It is tedious to do this each time, but it does allow me to successfully upload or commit when connected. (I also find that RDP connections fail much less often when the MTU is set correctly.) I should note that I pick an MTU value that is 100 less than the MTU value of the WIFI connection--it should be 78 but I opt for the easier math and don't really notice the difference. And for those that don't know, you can find the current MTU value of your connections by issuing the "ifconfig" command. If you do not have access to a cellular hotspot or other wifi connection that has a low MTU value, it is likely you can replicate this issue by manually setting the primary network connection's MTU value to 1430 (using the above command) though I have not tried to replicate it under these conditions. Ideally, the VPN connection would properly calculate an appropriate MTU value to use with the network adapter it will be communicating over. Perhaps it is trying that and simply cannot identify the proper connection--while writing this it occurs to me that the eth0 connection has an MTU value of 1500 even though I don't have a network cable plugged in, but lowering the eth0 MTU value had no effect on the tun0 MTU value chosen when I connected to VPN over the WIFI connection. To replicate the error: * connect to a wifi connection that gives you an MTU value of 1430 * connect to VPN using vpnc via network manager * verify that the MTU value of your tun0 connection was set to 1412 * Attempt a large upload (a large file, a large bugzilla comment or other html form submission, or a sizeable svn commit) and it should fail Important version info requested: Ubuntu 12.10 vpnc is 0.5.3r512-2ubuntu1 network-manager, network-manager-vpnc, and network-manager-vpnc-gnome are all 0.9.6.0-ubuntu1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1110787/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
