From: robbie (robbie@packetized.org)
Date: Sun Jul 11 2004 - 11:40:06 GMT-3
Hello again,
I understand how it works - and it's a super cool feature. But you can
use ip prefix-lists for things other than ORF, right? So in the
configuration example in the Cisco documentation, the prefix-list is
never specifically applied to a neighbor or ORF configuration, as far as
I can tell - can someone explain this in greater detail? EX:
RouterA#
ip prefix-list FILTER seq 10 permit 192.168.1.0/24
!
router bgp 100
address-family ipv4 unicast
neighbor 172.16.1.2 remote-as 200
neighbor 172.16.1.2 ebgp-multihop
neighbor 172.16.1.2 capability orf prefix-list send
exit
RouterB#
router bgp 200
address-family ipv4 unicast
neighbor 10.1.1.1 remote-as 100
neighbor 10.1.1.1 ebgp-multihop 255
neighbor 10.1.1.1 capability orf prefix-list receive
end
clear ip bgp 192.168.1.2 in prefix-filter
!
Where in this configuration is the prefix-list FILTER told that it is to
be used as part of the ORF configuration? It seems to me that you could
configure a prefix-list that's to be applied 'in' on one neighbor and
'out' on the other, but what if you set ORF capabilities to 'both' on
these, thus not clearly specifying what's to be filtered by your peer?
Just a bit confusing to me, and I've not yet had the chance to test this
in my lab. Thanks in advance. :)
Robbie
Joe Deleonardo wrote:
> Hi Robbie
>
> That was kind of my original question... by the way thanks Howard.
>
> If you configure the prefix list on one end it automagically by way of the
> ORF config, tells the sending router what should be sent.
>
> It's a pretty cool feature, saving CPU cycles on both routers, the only
> problem in the real world is that you have to have the eBGP peers'
> cooperation.
>
> Not a problem in the lab though. :)
>
> Have a good one,
>
> Joe
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> robbie
> Sent: Saturday, July 10, 2004 4:36 PM
> To: ccielab@groupstudy.com
> Subject: Re: BGP ORF
>
> I'm just now reading about the wonderful world that is ORF - something
> that I'm not at all familiar with. In the article mentioned, most of it
> makes sense, except for how the prefix-list 'FILTER' is applied to the
> ORF peering arrangement - can anyone clarify that for me? It doesn't
> seem too intuitive that one would create a prefix-list that's just
> automagically applied to the ORF instance in the address-family
> configuration without being mentioned.
>
> Thanks in advance,
> Robbie
>
> Howard C. Berkowitz wrote:
>
>
>>At 2:30 PM -0700 7/10/04, Joe Deleonardo wrote:
>>
>>
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120
>
>
>>>limit/120st/120st11/bgpbporf.htm
>>>
>>>Does anyone understand what's really going on here. At first glance it
>>>seems
>>>like a filter would do the same job.
>>>
>>>When I read into it, it almost seems like a peer that wants to accept
>>>limited routes from an eBGP peer sends a message that says "only send me
>>>these prefixes." Otherwise, if that's not the case, I don't see the
>>>benefit
>>>of doing this. You might as well use a regular filter.
>>>
>>>Can anyone confirm my suspicions about what's going on with this feature?
>>
>>
>>Sure. ORF causes your peer router to block routes it would otherwise
>>transmit and you would reject. At the first level, this saves bandwidth
>>that would be otherwise consumed by your inbound filter.
>>
>>When ORF is implemented widely, it lowers the overall filtering load on
>>all routers, since only desired traffic will be received.
This archive was generated by hypermail 2.1.4 : Sun Aug 01 2004 - 10:11:52 GMT-3