Hi,
Currently I have a wholesale connection to customer's through a 3rd party internet service provider. I use several vpdn-groups to the 3rd part company over an ATM connection.
Problem is we had a customer get onto to our wholesale DSL, and his L2TP VPN connection would not work, PPTP VPN connections work fine. After doing research I found that the MTU and ip tcp adjust-mss needed to be re-configured. I added ip mtu 1460 and ip tcp adjust-mss 1420 onto a virtual-template we use for each vpdn-group. After that the customer worked fine for a month, but suddenly his connection stopped working. After doing some ping tests we couldn't pass anything larger than 1432, which is too small. I played with the settings, but we'd lose connectivity to our other customers, so I ended up setting it back to what I had set it to before (ip mtu 1460 and ip tcp adjust-mss 1420) and suddenly I can pass 1452 size packets, and the customer's L2TP VPN conneciton is working again. It worked for another two weeks, and then it stopped working again.
The router I am using is a Cisco 7206VXR (NPE400) and the system image file is "disk0:c7200-js-mz.124-25e.bin".
Here is an example of our vpdn-groups:
vpdn-group 82
description XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
accept-dialin
protocol l2tp
virtual-template 1
terminate-from hostname XXXXXXXXX
local name XXXXXXXXXX
lcp renegotiation always
l2tp tunnel password 7 XXXXXXXXXXXXXXXXXXXXXXXXXX
...and the vritual-template looks like this:
interface Virtual-Template1
mtu 1460
ip unnumbered Loopback1
no ip redirects
no ip unreachables
no ip proxy-arp
ip tcp adjust-mss 1420
no snmp trap link-status
peer default ip address pool local1
keepalive 60
ppp authentication chap pap interface
Does anyone know if this is a Hardware problem, or a Software bug? Or is this some kind of negotiation issue with the MTU sizes?? Can anyone help me on this?
Thanks.
Christopher.
