From: Debashis Kundu (dkundu@xxxxxxxxx)
Date: Sun Sep 16 2001 - 21:59:52 GMT-3
Sorry I think you misunderstood. I am talking about the range command(ABR)
not summary-address(ASBR).
Please check the original problem.
In the ABR whenever summary routes are configured using range command it's
better to add a static route with null interface also because if you have
default route advertised by some other area this will avoid creating a
routing loop.
Please let me know if you need more explanation.
Deb
At 08:28 PM 9/16/2001 -0400, Nigel Taylor wrote:
>Debashis,
> See Inline...
>
>----- Original Message -----
>From: "Debashis Kundu" <dkundu@cisco.com>
>To: "Cade Wagner" <cwagner@logosinc.com>; <ccielab@groupstudy.com>
>Sent: Sunday, September 16, 2001 7:34 PM
>Subject: Re: OSPF Area Summary Question
>
>
> > Whenever summary routes are configured within an OSPF domain, be sure to
> > add a static route for
> > the summary address pointing to the null interface.
> >This is done to avoid
> > routing loops because it may happen that you don't have all the summary
> > addresses in your area so this is just design practise.
>
>Why would you add a static route to the null0 interface? Typically when the
>summary-address command is used it is done to pass/inform the OSPF
>routing domain about an external network. For the summary-route to be
>generated the router(typically an ASBR) must have a route for the network
>being summarized in it's local RIB. When the summary route(a type 5 LSA) is
>generated a route to null0 is placed into the local RIB to maintain the
>integrity of the routing information. Hence no need to create static
>routes.
>
> >This is done to avoid
> > routing loops because it may happen that you don't have all the summary
> > addresses in your area so this is just design practise.
>
>Short of being a stub, totally-stubby and a NSSA If all routers in the OSPF
>domain does not have the summary-route generated form the ASBR performing
>the summarization then you may a bigger problem in that all OSPF routers
>within normal/typical areas should synchronize and have identical Link-State
>databases. I think placing static routes to null0 in this case could
>complicate things for not so experienced network personnel. Now it will
>happen that if the router(ASBR) performing the summarization for some reason
>or another loses the route for the network being summarized then, yes the
>issue you mentioned would exist in which case none of the routers within the
>ospf domain will have a route for the specific network. In this case a
>typical 0/0 (default route or static route to the specified network) could
>possibly provide the connectivity to this otherwise reachable network.
>
>Anyone care to make any suggestions...or share possible experiences.
>
>Nigel
>
> >
> >
> > At 01:44 PM 9/16/2001 -0400, you wrote:
> > > Not sure what I am doing wrong, but I can never get the area 1
>range
> > >10.1.1.0 255.255.255.0 command to work.
> > >
> > > Many of the examples that I have seen have a route to Null0 for
>what
> > >is summarized. Is this necessary like in BGP for advertised networks?
>Will
> > >a route from another protocol like EIGRP work in its place? I have tried
>it
> > >all three ways with no success. Probably just overlooking something
>simple.
> > >Thanks for the help in advance.
> > >
> > > Cade Wagner
> > >**Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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