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null 0

what is null 0? is it always 0?

6 REPLIES

Re: null 0

Hi Friend,

Null 0 is a black hole when routes checks this interface it will not find any route and will drop the traffic.

Lets take an example of a route

ip route x.x.x.x x.x.x.x null0

If this is the route and any packet matches that destination it will be dropped cause null 0 is not a valid interface.

Have a look at this link

http://www.cisco.com/univercd/cc/td/doc/product/software/iosxr3/int_c3/hc3loop.htm#wp1349080

HTH, if yes please rate the post.

Ankur

New Member

Re: null 0

whats HTH?

Re: null 0

Hi Friend,

HTH is hope that helps ;)

Regards,

Ankur

New Member

Re: null 0

I'm having problems with 'route null0' statics being propagated through our MPLS / EIGRP / BGP network even when I do not have default-info-originate commands under the routing protocols

Cisco80211

Chris Serafin

IT Security / Cisco VoIP Engineer

chris@chrisserafin.com

Re: null 0

Hi Friend,

Have you configured your EIGRP with summarization?

Regards,

Ankur

New Member

Re: null 0

Hi,

Static route pointing to an interface (in your case, Null0) is considered directly connected network.

E.g. if you have "ip route 10.0.0.0 255.0.0.0 Null0", then you'll see the following line when you do "show ip route":

S 10.0.0.0/8 is directly connected, Null0

If the "network" command of your EIGRP covers the above network, it will be advertised as internal EIGRP route (AD=90).

Hope this helps.

Thank you.

B.Rgds,

Lim TS

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