Re: OER External interface Null0

Marko,
Thank you for your response.

I did find one reference of the null interface as a next hop with an
OER-map
http://www.cisco.com/en/US/docs/ios-xml/ios/oer/configuration/12-4t/oer-cfg-apply.html#GUID-5592C6F1-2C89-4197-A6DD-ABF807025579
but for this feature to work I don't think you have to setup Null0 to be an
*external interface*. Basically they are saying this is a black hole policy
for a specified prefix traffic-class.

Config from the link:

enable
configure terminal
ip prefix-list PREFIX_BLACK_HOLE seq 10 permit 10.1.5.0/24
oer-map BLACK_HOLE_MAP 10
 match ip address prefix-list PREFIX_BLACK_HOLE
 set interface null0
 end

Regards,

Tom

On Mon, Mar 26, 2012 at 9:46 PM, Marko Milivojevic <markom_at_ipexpert.com>wrote:

>
> That's a good question. If you have only one external interface, what's
> the point of PfR to begin with? So, I'm thinking that the reasons are not
> just making 2nd interface appear, even though I might be wrong. I'm more
> thinking of a possibility to use that as an exit interface to drop certain
> traffic if a condition is met. I'd struggle coming up with a scenario to
> use it in real life though.
>
> --
> Marko Milivojevic - CCIE #18427 (SP R&S)
> Senior CCIE Instructor - IPexpert
>
> On Mon, Mar 26, 2012 at 18:27, Tom Kacprzynski <tom.kac_at_gmail.com> wrote:
>
>> Hello,
>> I noticed that you can specify a Null0 interface as an external interface
>> in OER. Does anyone know where you would use that?
>>
>> The only thing I could see that being used for is if you have to shutdown
>> one of the border routers and your total number of external interfaces
>> drops below 2 (which causes the master controller to become inactive). By
>> configuring a null0 interface as an external interface, the master
>> controlled comes up as active.
>>
>> Are there any other instance where that would make sense to configure a
>> null0 as an external interface?
>>
>> r3(config-oer-mc-br)#interface null0 external
>>
>>
>> Thanks
>>
>> Tom
>>
>>
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Received on Mon Mar 26 2012 - 22:08:31 ART