[Isis-wg] New version of draft-ietf-isis-domain-wide-02.txt

[Henk Smit]

> Henk Smit <hsmit@cisco.com> writes:
> 
> >   Here is the new draft for route-leaking with old-style TLVs.
> [...]
> >    Based on these assumptions, this document defines the following route
> >    preferences.
> > 
> >     1) L1 intra-area routes with internal metric
> >        L1 external routes with internal metric
> >     2) L2 intra-area routes with internal metric
> >        L2 external routes with internal metric
> >        L1->L2 inter-area routes with internal metric
> >        L1->L2 inter-area external routes with internal metric
> >     3) L2->L1 inter-area routes with internal metric
> >        L2->L1 inter-area external routes with internal metric
> >     4) L1 external routes with external metric
> >     5) L2 external routes with external metric
> >        L1->L2 inter-area external routes with external metric
> >     6) L2->L1 inter-area external routes with external metric
> 
> I believe that currently the draft doesn't specify how to leak routes
> derived from both types of reachability.  Since the reachability doesn't 
> play a part in route selection this could conceivably happen.
> 
> This is not described in rfc 1195 because level 1 wasn't defined to have 
> external reachability and level 2 didn't leak into level 1.
> 
> I think a perfectly reasonable action would be to always choose internal
> (i.e., TLV 128) if the route was derived in full or in part from a TLV
> 128 prefix.
> 
> Does this sound reasonable?

  Yes, this sounds reasonable.
 I will add some text to describe this.

  Note, if you see the same prefixes as both internal and external,
 your network already seems to be experiencing redistribution feedback.
 Not a good thing to begin with.

     Henk.


> Thanks,
> Chris.
>