[c-nsp] Load Balancing, Part II

[Roy]

Oliver Boehmer (oboehmer) wrote:

>>Thanks to all who responded on my load balancing question on different
>>protocols.  Now onto part II of the quiz :-)
>>
>>I have two routers R1 and R2 attached to a single customer C.  The
>>routers are connected via BGP with R1 and R2 as members of a
>>confederation.  I would like to load balance between the path R1-C and
>>R1-R2-C.
>>
>>show ip bgp 1.1.1.0
>>BGP routing table entry for 1.1.1.0/24, version 8665091
>>Paths: (2 available, best #1, table Default-IP-Routing-Table)
>>Multipath: eBGP iBGP
>>  4000
>>    1.2.0.1 from 1.2.0.1
>>      Origin IGP, metric 0, localpref 100, valid, external, best
>>  (65002) 4000
>>    1.3.0.1 (metric 20) from 1.3.0.1
>>      Origin IGP, metric 0, localpref 100, valid, confed-external
>>
>>BGP doesn't seem to want to install both routes.  The AS length is the
>>same since the confederation AS (65002) gets removed.  How can one
>>determine why it won't multipath?
>>    
>>
>
>I'm not entirely sure if we're supposed to do multi-path in this
>situation as confed paths are treated as "internal" in the comparison
>(see Step 7 in http://www.cisco.com/warp/public/459/25.shtml), and eiBGP
>multipath only works for vpnv4 paths.
>
>You could try to configure the hidden command "bgp bestpath
>multipath-relax as-path" (if it is available in the release you are
>running) to see if it makes a difference, but I don't think it will
>help.
>
>	oli
>
>  
>
I don't have the command.  I am on 12.2(15)T5.

I did look up

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml#bgpmpath

Which could seem to insinuate that confed-external paths are treated as 
external for multipath

"The path should be learned from an external or confederation-external 
neighbor (eBGP)."