From: Matt Smith (matt-n-donna@xxxxxxxxxxxxxx)
Date: Wed Nov 28 2001 - 23:01:16 GMT-3
It is designed to prevent a routing loop which could occur if you inject a
supernet to which all included routes arent accounted for I beleive. For
example
r1 -----------r2-----------r3
R1 has ip addresses 10.1.1.0 - 10.1.9.0 and neighbors with r2 in area 2
R2 enters an area 2 range 10.1.0.0 255.255.240.0 (summarizing 10.1.1.0 -
10.1.15.0) and neighbors with r3 in area 0
R3 issues default information originate so that r2 has a 0/0 route pointing
to r3
So...now R3 pings an address at 10.1.10.0 which doesnt really exist. Since
it falls within the summary r3 sends the packet to R2. R2 doesnt have a
route for the network 10.1.10.0 so it uses the 0/0 route back to
R3...and...boom..routing loop. Now you can see what the null route would
do. By creating this than it would bit bucket all routes not expicity in
the routing table thus preventing the loops.
Thats my understanding at any rate.
Experts please advise if I am mistaken
Luck to All
Matt Smith
----- Original Message -----
From: "Jaspreet Bhatia" <jasbhati@cisco.com>
To: <ccielab@groupstudy.com>
Sent: Wednesday, November 28, 2001 7:51 PM
Subject: OSPF Summarization
> While doing OSPF summarization on an ABR with the area range command ,
what
> is the function of including a static route pointing to the NULL interface
?
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