From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Wed Aug 10 2005 - 04:17:05 GMT-3
2cents on this discussion.
For EIGRP connected to OSPF at 2 points, both performing mutual
redistribution, no tags, filters or admin distance manipulation is
required to stop route feedback, the EIGRP external distance takes care
of that. Before loking at these three methods it is best to understand
why none of them are necessary in this scenario first.
Regarding the area issue on ISIS, there was a thread on this a few weks
back ,where it was identified that the first byte is the AFI, with a
maximum value of 99. I asked a manager in the CCIE program about whether
we should configure area 17 (converting to hex) as
00.0011.aaaa.aaaa.aaaa.aaaa.bb or just go with 11.aaaa.aaaa.aaaa.aaaa.bb
and the answer came back that they are really looking at the routes in
the routing table more than how the raeas are configured at this point,
so given ISIS is leaving the exam, it's probably not a big deal how they
are chosen, as long as route exchange works.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
James Keane
Sent: Tuesday, August 09, 2005 8:47 AM
To: Rohan Grover (rohang); Group Study
Subject: Re: Some questions...
regarding ISIS, remeber your HEX so area 47 is 2F etc
regarding loops ...
the way I understand it, you only need to stop a loop in one place, so
if you tag it on one 'crossroads' you can enforce it on the other. so
your example
R1---------R2-------------R4
| OSPF EIGRP |
|-----------R3-------------|
We shall TAG on R2 in the redistribution so
router eigrp
redistribute ospf metric 1000 .(etc).. route-map O2E route-map O2E
permit 10 set tag 10
router ospf 1
redistribute eigrp subnets route-map E2O route-map E2O permit 10 set tag
20
on R3 we shall prevent feedback
we need to redistribute from O2E and PREVENT the eigrp (now ospf
externals) coming in, luckily we have taged them with 20.
so we
route-map O2E deny 10
match tag 20
route-map O2E permit 20
like wise on R3 we need to prevent the feedback the other way, so the
ospf routes (now external EIGRP with
10) need to be filtered
so
route-map E2O deny 10
match tag 10
route-map E2O permit 20
2: Tips, using the protocols admin distances like you did is bound to
lead to to confuse tags with admin distances, think of tagging like
colouring .. it does nothing by itself, but we can use the colours to
help identifiy the source of a route.
Hope it helps !
James
This archive was generated by hypermail 2.1.4 : Sun Sep 04 2005 - 17:01:18 GMT-3