> Is there a Cisco's IS-IS mailing list.
> If so how can I subscribe to it.
Nope, there is no such list.
> It seems to me that there is some interesting discussion going on
> in IS-IS outside this mailing list.
Not that I know of.
There is the SIF forum (Sonet Interoperability Forum).
For the rest all progress is reported to this list, and discussed
at the IETF ISIS WG meetings.
Henk.