Re: Question about BGP Aggregate with AS-SET

With your /7, both candidate routes have the same AS Path.

With the /5, there is variety and therefore a concatenation (AS
Sequence/Set) needs to be performed.

Same, but different. ;)

HTH,

Scott

mohmmad imran wrote:
> Hi Experts,
>
> I have three router in AS 100
>
> R1=Fa0/0-----------------Fa0/0=R2
> |
> |
> Fa0/0
> |
> R3
>
>
> R1 is getting the route 112.0.0.0/8 to 119.0.0.0/8 from as-path 54 50 60 and advertsie it to R3
>
> R1 SH IP BGP Output:-
>
> *> 112.0.0.0 1.1.1.254 0 0 54 50 60 i
> *> 113.0.0.0 1.1.1.254 0 0 54 50 60 i
> *> 114.0.0.0 1.1.1.254 0 0 54 i
> *> 115.0.0.0 1.1.1.254 0 0 54 i
> *> 116.0.0.0 1.1.1.254 0 0 54 i
> *> 117.0.0.0 1.1.1.254 0 0 54 i
> *> 118.0.0.0 1.1.1.254 0 0 54 i
> *> 119.0.0.0 1.1.1.254 0 0 54 i
>
>
> R3 SH IP BGP Output:-
>
> *>i112.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> *>i113.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> *>i114.0.0.0 1.1.1.254 0 100 0 54 i
> *>i115.0.0.0 1.1.1.254 0 100 0 54 i
> *>i116.0.0.0 1.1.1.254 0 100 0 54 i
> *>i117.0.0.0 1.1.1.254 0 100 0 54 i
> *>i118.0.0.0 1.1.1.254 0 100 0 54 i
> *>i119.0.0.0 1.1.1.254 0 100 0 54 i
>
>
> If try to aggregate above subnets into one prefix on R1 with:-
>
> router bgp 100
> aggregate-address 112.0.0.0 248.0.0.0 summary-only as-set
>
> I can see that the router is setting up the AS-SET in BGP table, as per below output:-
>
> s>i112.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> *> 112.0.0.0/5 0.0.0.0 100 32768 {54,50,60} i
> s>i113.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> s>i114.0.0.0 1.1.1.254 0 100 0 54 i
> s>i115.0.0.0 1.1.1.254 0 100 0 54 i
> s>i116.0.0.0 1.1.1.254 0 100 0 54 i
> s>i117.0.0.0 1.1.1.254 0 100 0 54 i
> s>i118.0.0.0 1.1.1.254 0 100 0 54 i
> s>i119.0.0.0 1.1.1.254 0 100 0 54 i
>
> but instead of aggregating all route,if I try to aggregate 112.0.0.0/8 and 113.0.0.0/8 into on 112.0.0.0/7 prefix, router generate the aggregate prefix in BGP table instead of showing the AS-SET it shows the AS-PATH-SEQ on aggregated prefix.
>
> router bgp 100
> aggregate-address 112.0.0.0 254.0.0.0 summary-only as-set
>
> s>i112.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> *> 112.0.0.0/7 0.0.0.0 100 32768 54 50 60 i
> s>i113.0.0.0 1.1.1.254 0 100 0 54 50 60 i
> *>i114.0.0.0 1.1.1.254 0 100 0 54 i
> *>i115.0.0.0 1.1.1.254 0 100 0 54 i
> *>i116.0.0.0 1.1.1.254 0 100 0 54 i
> *>i117.0.0.0 1.1.1.254 0 100 0 54 i
> *>i118.0.0.0 1.1.1.254 0 100 0 54 i
> *>i119.0.0.0 1.1.1.254 0 100 0 54 i
>
>
> I tried it on two differenet IOS version with same result,I am missing something here?
>
> -Imran
>
>
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Received on Sun Apr 18 2010 - 03:32:43 ART