I am still seeing this problem in 14.10, even installed fresh on a new laptop. I have found a workaround that takes care of the problem automatically, though. There is a 1412 mtu hardcoded in /etc/vpnc/vpnc- script, but that may not be relevant to network manager so I didn't mess with that script. The NetworkManager man page notes that any scripts placed in /etc/NetworkManager/dispatcher.d will run when network connections go up and down, and that they will receive the name of the interface and the action as parameters to the script. So I placed the following script in that directory under the name "70vpnMtuCorrection" (the scripts run in alpha order, and there was already one more there so I wanted this one to run later...but you can call it anything else you like and it should still work). The script needs to be owned by root and executable by all (so use sudo to save it and execute a "chmod a+x" on the file"). The script determines if the tun0 interface is coming up, if we have a wlan0 connection, calculates the necessary mtu value, and resets it if the MTU value needs to be decreased. This seems to be handling my issue, but I would still prefer to see that it is handled properly by network manager in the first place. But if you are having the same problem, this should remove a pesky annoyance like it is doing for me:
/etc/vpnc/vpnc-script/70vpnMtuCorrection: #!/bin/bash TUN0_INTERFACE_NAME="tun0" WLAN0_INTERFACE_NAME="wlan0" VPN_UP_ACTION_NAME="vpn-up" MTU_DIFFERENCE=78 INTERFACE_NAME=${1} ACTION=${2} if [ "${INTERFACE_NAME}" != "${TUN0_INTERFACE_NAME}" ] then exit 0 fi if [ "${ACTION}" != "${VPN_UP_ACTION_NAME}"] then exit 0 fi #Make sure we have a current TUN0 entry before we continue. CURRENT_TUN0_MTU=`sudo ip link list | grep "${TUN0_INTERFACE_NAME}:" | sed -r "s/.*mtu ([0-9]+).*/\1/"` if [ "${WLAN_MTU}" == "" } then exit 0 fi #Also make sure we have a current WLAN0 entry WLAN_MTU=`sudo ip link list | grep "${WLAN0_INTERFACE_NAME}:" | sed -r "s/.*mtu ([0-9]+).*/\1/"` if [ "${WLAN_MTU}" == "" } then exit 0 fi NEW_TUN0_MTU=$((${WLAN_MTU} - ${MTU_DIFFERENCE})) if [ ${NEW_TUN0_MTU} >= ${CURRENT_TUN0_MTU} ] then exit 0 fi ip link set ${TUN0_INTERFACE_NAME} mtu ${NEW_TUN0_MTU} -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1110787 Title: VPN tunnel connections are not properly setting MTU values To manage notifications about this bug go to: https://bugs.launchpad.net/network-manager/+bug/1110787/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs