Null Routes- And when it's safe to remove

From: Chris Hugo (chrishugo@yahoo.com)
Date: Sat Sep 07 2002 - 07:37:52 GMT-3

Hi Folks,

I have a quick question that somebody can probably clarify in a heartbeat.

Let's say you have two routers:

routera------routerb

routerb has the following routes in it's routing table:

192.168.100.0/24

192.168.200.0/24

192.168.300.0/24

Now on routerb I want to create A summary route using any IGP routing protocol.

The summary route is:

192.168.0.0/16

By default a routing protocol will summarize that route and propagate the summarized route.

Now what also happens is a null route is also from that specific routing protocol into the router that originated the route. Of course this makes cent$ to avoid a routing loop.

Now if routerb has a default route to router and routerb happens to lose ONE route to 192.168.1.0 a routing loop will easily form without a null route on routerb to 192.168.0.0.

OK, now let's eliminate the default route on routerb but the summary route is still propagated from routerb. Is it totally safe to say I can remove the summary route without creating Possible routing loop if one route happens to fail. I know how to remove this route that is not my concern.

I want to know if it is safe to remove this null route in this condition....

Thank U..

chris hugo

 

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