From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Thu Jan 11 2001 - 02:20:43 GMT-3
Darren,
I understand what a summary route is and what it does, as well the
configuration commands required however, the question still stands as to
what is the meaning of the route that is in the table.
i su 172.16.0.0/16 [115/30] via 0.0.0.0, Null0
comapred to the average summary route...
O 182.18.0.0/16 is a summary, 10:01:24, Null0
Do you not see the difference...! Now this is working as far as I can tell
because all the routers in the ISIS domain get the summarized route to the
OSPF domain and can effectively ping and trace to all point therein. Could
this just simply be the way ISIS defines a summary route..? Not a whole lot
of examples to reference...:-)
Nigel..
It's seems quite logical that I move on to the next problem... Noted by some
of our newly minted CCIE's. Pratice makes perfect...:-)
>From: dward@ns.pla.net.au
>Reply-To: dward@ns.pla.net.au
>To: Chuck Larrieu <chuck@cl.cncdsl.com>
>CC: Nigel Taylor <nigel_taylor@hotmail.com>, cisco@groupstudy.com,
>ccielab@groupstudy.com
>Subject: RE: ISIS and OSPF redistribution Weirdness - Update
>Date: Thu, 11 Jan 2001 11:29:07 +1100 (EST)
>
>This is a generated summary route for the class which as a summary is
>routed via null0.
>
>Remember a route only gets entered into the table or advertised if it
>exists so all summaries get routed to null0 which is the bit bucket
>interface and that way the 'route' is active.
>
>If this is a problem turn off classful routing and/or remove auto-summary.
>
>This behaviour also occurs in EIGRP and you have to turn off auto-aummary
>or you'll advertise a summary route to other networks not part of the
>summary range.
>
>You can also see the same behaviour by manually configuring summarization
>such as 'ip summary-address eigrp 1 1.1.1.0 255.255.252.0'
>then look at the summary route as it it appears in the routing table.
>
>Darren
>
>On Wed, 10 Jan 2001, Chuck Larrieu wrote:
>
> > i su 172.16.0.0/16 [115/30] via 0.0.0.0, Null0
> >
> >
> > Nigel, the other interesting thing about this route as I see it, is the
>last
> > part of the line.
> >
> > The source is IS-IS, the su maybe we are guessing it is short for
>summary,
> > but we don't know, and then we get to that route via 0.0.0.0 comma null0
> > Without looking at some router output, this looks a bit unusual as well.
> > Want to call it one of those Cisco things?
> >
> > I did not see a route to 0.0.0.0 in either of your show ip route
>outputs.
> > IS-IS level one routers, if my recollection is correct, are analogous to
> > OSPF stub area. In fact, it seems to me that on one of tests, I actually
>saw
> > a 0.0.0.0 route generated by a level 1 router. did you spot anything
>like
> > this on any of your level 1's?
> >
> > I will certainly keep an eye out when I set up next time.
> >
> >
> > Chuck
> >
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:27:27 GMT-3