can anyone help with my understanding (or lack of !) as to how an IOS host calculates or determines the path mtu (ip mtu) as is reported by "show crypto ipsec sa"
the observed behaviour is one of values that seem to vary over time, and also with values not necessarily the same at each end
i suspect perhaps issues of inconsistency between different IOS versions at each end;
c1700-advsecurityk9-m (version 12.4(3) c837-k903sy6-m (version 12.3(2)
also for ref we are running both connection on PPPoA (broadband supplied by BT) on both ends so i assume the physical network characteristics to be the same.
Thanks