[cisco-bba] IOS upgrade kills Linksys

[Krzysztof Adamski]

I upgrade my LNS from 12.2(12f) to 12.2(15)T14, and now some LinkSys boxes
are showing weird behaviour. The LNS is doing PPPoE aggregation.
 All the normal web access is working, but a VPN access to an exchange
server is not. The VPN software is running on a PC behind the LinkSys. The
VPN packets are encapsulated in UDP.
 Not all VPN is the problem just the exchange traffic. Snooping the
traffic it appears that the exchange is sending a 18k size UDP packet that
is being fragmented. The size of each fragment is 1492 bytes. For some
strange reason the MTU on the virtual-interface is 1464, this is how my
virtual-template looks:

interface Virtual-Template1
 ip unnumbered FastEthernet1/0
 no ip proxy-arp
 mtu 1492
 ip tcp adjust-mss 1300
 no logging event link-status
 peer default ip address pool ADSL
 ppp authentication pap

I have tried ip mtu 1492, mtu 1500, mtu 1464, even changing the MTU on the
LinkSys to 1464 nothing helped.

Any ideas what can be wrong?

K