I have a 2611 with c2600-ik9o3s3-mz.123-15.bin IOS.
It suports only ssh version 1.5 (I know only version 1 and 2 nothing in the middle). I built a VPN over it. Well it seems to me that VPN (remote as initiator) doesn't succeed. It only succeed if I try to connect via ssh to the router. I tried to turn on crypto debugging and every time I turn on it all tentatives succeed.
It seems to me that trying to contact the router via ssh or enabling crypto feature debugging wakes up crypto engine.
Has anyone of you experienced these problems?