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New Member

routing to Null0


What's the purpose of doing a ip route to null0 ?



  • Other Network Infrastructure Subjects
Cisco Employee

Re: routing to Null0

There is several reasons why one might want use a static route to null0. Here are a couple.

- You want to originate a summary route in BGP and you want to make sure that if a more specific exist doesn't exist in the routing table traffic will be dropped. This will also cause the BGP advertisement to be very stable since the static route to null0 will never go down.

- The static route to null0 is sometimes use to purposely drop traffic in DDOS attack scenarios.

Hope this helps,

New Member

Re: routing to Null0

for the 1st part, am i right to say like that :

Router A is publishing a summary route x.x.x.0/25 to Router B but at the Router B's end, i can route the part of the segment x.x.x.0/25 to NULL0 if there's none of that segment exist?

Cisco Employee

Re: routing to Null0

In this case, router A would be the one using the static route to null0, not router B. So router B would forward packets to router A and router A would drop the packets if it didn't have a more specific route for that /25.

Hope this helps,

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