A summary route to null0 can prevent a routing loop to form.
Imagine a situation where there is a default route as well in the routing table.
If a packet comes in destined for a subnet that resides in the summary range, and there is no specific prefix for it in the routing table and you don't have a summary route pointing to null0, what happens?
You guessed right:
It will go out on the default route.
And what if the default route directly or indirectly points back to the router where the packet came from? That router will route the packet back to this router again.
Well, this is a nice routing loop.
So, if you have a summary route pointing to the null0 interface, this packet will have a match on it and will be dropped (if there is no explicit route for the more specific subnet in the routing table).
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
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IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
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