Null 0

Unanswered Question
Feb 27th, 2007

I have a quick question when you do a static route what is the meaning of Null 0 at the end...eg:

ip route 65.219.101.0 255.255.255.0 Null0

I have this problem too.
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ahmednaas Tue, 02/27/2007 - 07:14

The trash can of cyberspace.

Those packets will be effectively discarded.

deilert Tue, 02/27/2007 - 07:26

Null 0 is generally used for summarization with the expectation that when the packet reaches the router generating the Null 0 route a more specific route will exist.

For example if you have a route

ip route 65.219.101.0 255.255.255.0 Null0

and you are trying to reach 65.219.101.66, you would want a route to 65.219.101.64/x to exist. That way the packet will not be dropped it will be routed to the more specific route.

shantharam.sury... Wed, 02/28/2007 - 01:59

Hi,

There are two things

1. 65.219.101.0/24 belongs to you, ip route 65.219.101.0 255.255.255.0 Null0 means you are advertising your IP block to internet

2. 65.219.101.0/24 does not belongs to you, ip route 65.219.101.0 255.255.255.0 Null0 means any packets coming from that block will be dropped at your wan interface.

Regards

S. Shantharam

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