Unable to create interface null0

Unanswered Question
May 5th, 2008

Hey guys,

I keep getting the

% route-map:can not set interface.

% Use P2P interfaces for set interface clause

every time I try to set ("set interface null0") a null interface inside a route map.

Has anyone seen this?

My route map is:

route-map MY-LOCAL-POLICY permit 10

match ip address 150

set ip next-hop 98.98.98.98

In this route map, I want to add the set interca null0 command but it gives me those errors messages.

thanks

I have this problem too.
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Paolo Bevilacqua Mon, 05/05/2008 - 19:54

Hi, why do you want to use null0 in route-map ? Null0 can be used only for certain purposes, eg permanent static routes for bgp, or packet discard.

guruprasadr Tue, 05/06/2008 - 02:25

HI, [Pls Rate if HELPS]

If your requirement is to block certain IP @ Address: The below is the Example Config:

Create an ACL:

R2(config)#access-list 30 permit host 20.2.2.2

R2(config)#access-list 31 permit host 20.3.3.3

Perhaps if you want to specifically block traffic sourced from 20.3.3.3 or 20.4.4.4. You can use multiple match statements in one single route map, and have packets matching those two addresses sent to the bit bucket - the interface null0.

R2(config)#route-map EXAMPLE permit 30

R2(config-route-map)#match ip address 31

R2(config-route-map)#match ip address 32

R2(config-route-map)#set interface null0

Any traffic matching ACLs 31 or 32 will be sent to null0, resulting in its being discarded by the router. Any traffic that didn't match any of the route map statements will be returned to the routing engine for normal processing.

Hope I am Informative.

Pls RATE if HELPS

Best Regards,

Guru Prasad R

Giuseppe Larosa Tue, 05/06/2008 - 11:35

Hello,

if you want traffic matching the access-list 150 to be sent to null0 why you want also to set an ip next-hop at the same time ?

I guess that if you remote the set ip next-hop you will be able to use the set interface null0 in this route-map clause.

there is no sense in setting an ip next hop if you want to discard traffic.

Of course I may be wrong, but experience says that it is not possible to use any combination of commands inside a route-map.

In this case if you set a next hop the IOS code treats the outgoing interface as multiaccess and does not allow you to use set interface that can be used for serial point-to-point interface only.

null0 is a logic interface for a waste bin.

hope to help

best regards

Giuseppe

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