Re: Outbound Route Filtering

 Hi,

ORF is a capability by which your router, R1 as per your diagram advertises
which prefix it want to recieve from R2 or in other words AS 1 is "sending"
a prefix-list of what routes it wants, while AS 2 is "receiving" the
prefix-list of what the downstream neighbor wants.

As per your scenario R2 (AS2), the only additional command required is
"capability orf prefix-list receive".
And of course at R1(AS1) we need to specify what prefix we want, in your
case 172.16.1.0/24 and you send the prefix list which you want with
"capability orf prefix-list send".

Without send prefix list at R1, R2 will advertise all the networks to R1.

If you configure capabilty orf prefix-list both, then the router will have
the capability to send and recieve prefixes.(two-way)

If i remember theres a wonderful article in INE blog on this, dont miss that
!

Tharak Abraham

On Sun, May 17, 2009 at 8:38 PM, CCIE Hunter <cisco.ccie.guru_at_gmail.com>wrote:

> Hi group,
> R1(AS1)-------------------R2(AS2).
>
> R2 have prefix that need to advertise to R1. Then i configured R1 as send
> mode & prefix-list in & R2 as received mode. Everything working fine &
> config as follow.
>
> R1#sh run | b router bgp
> router bgp 1
> no synchronization
> bgp log-neighbor-changes
> neighbor 10.1.1.2 remote-as 2
> neighbor 10.1.1.2 capability orf prefix-list send
> neighbor 10.1.1.2 prefix-list 20 in
> no auto-summary
> !
> ip prefix-list 20 seq 5 permit 172.16.1.0/24
>
> *****
>
> R2#sh run | b router bgp
> router bgp 2
> no synchronization
> bgp log-neighbor-changes
> network 172.16.1.0 mask 255.255.255.0
> network 192.168.1.0
> neighbor 10.1.1.1 remote-as 1
> neighbor 10.1.1.1 capability orf prefix-list receive
> no auto-summary
> !
>
> But is it possible R2 will advertise prefix & control what prefix to be
> advertise with ORF feature. means without touching anything at R1(even
> don't
> configure send mode) ???
>
> And when do we need to use " neighbor x.x.x.x capability orf prefix-list
> both" ???
>
> I already browse at cco doc but still confusing send&receive mode.
>
> Please, and appreciate for advice
> Regards
>
>
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>
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Received on Mon May 18 2009 - 00:12:13 ART