I have two routers CISCO2801 (12.4(9)T6, ADVIPSERVICESK9) and a CISCO1841 (12.4(25f), ADVIPSERVICESK9).
IPv6 is configured on both routers and works fine over the internet. Now I had some some trouble to setup IPSec on the 1841 router. On the 2801 I configured the ipv6 peer as follows:
crypto isakmp key 0 12345 address ipv6 X:X:X:X::X/<0-128> Peer IPv6 prefix
on the 1841 I'm not able to configure the ipv peer. There is no address ipv6 option only for ipv4.
crypto isakmp key 0 12345 address A.B.C.D Peer IP address
Is this not a supported feature on the 1841?
IPv6 IPSec support wasn't added in IOS until 12.4(4)T, so 12.4(25f) (12.4 mainline code) does not have it. You will need to upgrade to 12.4T code before you can configure this. Please see: