[c-nsp] Preventing IS-IS adjacencies over 1Q trunk

Bruce Pinsky bep at whack.org
Mon Aug 20 21:06:17 EDT 2007


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Oliver Boehmer (oboehmer) wrote:
> Bruce Pinsky <> wrote on Thursday, August 16, 2007 10:45 PM:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Justin Shore wrote:
>>> I have a situation with IS-IS that's perplexing me.  I have a pair of
>>> core routers connected via an etherchannel.  The etherchannel is
>>> also a 1Q trunk.  The core routers have both routed connections to
>>> other routers as well as common VLANs w/ HSRP for non-router
>>> devices.  My intention was to build and IS-IS adjacency over the
>>> native VLAN on the trunk.  However I noticed that both routers are
>>> building adjacencies over 3 different VLANs that are permitted over
>>> that trunk.  All 3 SVIs have IS-IS enabled on them. 
>>>
>>> I'm assuming that I probably shouldn't have IS-IS enabled on the SVIs
>>> but is redistributing connected interfaces that appropriate solution?
>>> I'm trying to eliminate as much redistribution as possible.  Is
>>> there a better way to handle this?  I do need L2 between the chassis
>>> for the non-routed links. 
> 
> passive-interface VlanX 
> passive-interface VlanY
> 
> But nothing necessarily wrong with redistributing the connected
> (possibly along with a route-map filter), both options would produce
> basically the same result.
> 

I personally don't like the externals, but that's me.

>> If your IOS version supports it, you could use the
>> "advertise-passive-only" option in IS-IS.
> 
> Bruce, what do you mean? This reduces the ISIS IP prefixes to a minimum,
> but not sure if it addresses Justin's goal..
> 

My bad Oli....I was thinking he only cared about the VLAN interfaces not
considering there were other active IS-IS speakers on the box.

- --
=========
bep

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.4 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFGyjqIE1XcgMgrtyYRAsj4AJ9XhwX8jpQ2rnVzzFSN8siS1fnVLACgs9L0
DDGeG0wgOgrYdS/WH1C2ong=
=lGX9
-----END PGP SIGNATURE-----


More information about the cisco-nsp mailing list