[c-nsp] Load balancing outbound traffic with BGP

[Jeff Chan]

Quoting oles at ovh.net:

> On Tue, Feb 26, 2008 at 10:07:56PM +0100, Matyas Koszik wrote:
>>
>>
>> You may want to try
>>
>> bgp bestpath as-path multipath-relax
>
> not available on 6509/sup720BXL
>
> Router(config-router)#bgp bestpath ?
>   compare-routerid  Compare router-id for identical EBGP paths
>   cost-community    cost community
>   med               MED attribute


Apparently it's a hidden command, and our IOS/hardware took it:

#sh ver
[...]
Cisco IOS Software, 7200 Software (C7200-PK9U2-M), Version 12.4(10),  
RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 16-Aug-06 07:33 by prod_rel_team

ROM: System Bootstrap, Version 12.3(4r)T3, RELEASE SOFTWARE (fc1)
BOOTLDR: 7200 Software (C7200-KBOOT-M), Version 12.3(15b), RELEASE  
SOFTWARE (fc1)

router01 uptime is 1 year, 18 weeks, 6 days, 10 hours, 19 minutes
System returned to ROM by power-on
System restarted at 16:56:45 CDT Wed Oct 18 2006
System image file is "disk2:c7200-pk9u2-mz.124-10.bin"
[...]

Cisco 7206VXR (NPE-G1) processor (revision B) with 983040K/65536K  
bytes of memory.
Processor board ID 21280913
SB-1 CPU at 700MHz, Implementation 1025, Rev 0.2, 512KB L2 Cache
6 slot VXR midplane, Version 2.1
[...]


#sh conf

router bgp xxxx
  no synchronization
  bgp always-compare-med
  bgp log-neighbor-changes
  bgp bestpath as-path multipath-relax
  bgp bestpath compare-routerid
  bgp dampening



Yet:

#bgp bestpath ?
   compare-routerid  Compare router-id for identical EBGP paths
   cost-community    cost community
   med               MED attribute


Jeff C.


>> to achieve load-sharing accross the providers, with different (but equal
>> length) as-paths. (Works for me like a charm in a situation similar to
>> yours.)
>>
>>
>>
>>
>> On Tue, 26 Feb 2008, Jeff Chan wrote:
>>
>> > Hi All,
>> > Given multiple, roughly equal upstreams (Sprint, ATT, Level3)
>> > providing full BGP tables to a small ISP, what's the best way to
>> > balance the outbound traffic?  The problem is that all else being
>> > equal (path length, local pref, etc.) BGP decides to take the one with
>> > the lowest peering IP address.  Given that the upstreams have
>> > many/most of the same customers and peers, the peer with the lowest IP
>> > address seems to win too often, meaning it does too much outbound
>> > compared to the others.
>> >
>> > I asked the same question some time ago and the common practice answer
>> > seemed to be prefer traffic for some other large networks (UUNet,
>> > Qwest, AOL, etc.) over the peers with higher IP address.  Is this
>> > still the case?  Seems kind of an ugly hack, but it works.
>> >
>> > Are there any other approaches?  How about jumbling up or staggering
>> > the local preferences:
>> >
>> > ISP S:
>> >
>> > customers: localpref 120
>> > peers:     localpref 110
>> > others:    localpref 100
>> >
>> > ISP A:
>> >
>> > customers: localpref 110
>> > peers:     localpref 100
>> > others:    localpref  90
>> >
>> > ISP L:
>> >
>> > customers: localpref 100
>> > peers:     localpref  90
>> > others:    localpref  80
>> >
>> > Where S has the highest IP address, A next highest, L lowest.  Haven't
>> > tried this; just a thought to try to compensate for the IP address
>> > decision.
>> >
>> > Cheers,
>> >
>> > Jeff C.
>> >
>> > _______________________________________________
>> > cisco-nsp mailing list  cisco-nsp at puck.nether.net
>> > https://puck.nether.net/mailman/listinfo/cisco-nsp
>> > archive at http://puck.nether.net/pipermail/cisco-nsp/
>> >
>>
>> _______________________________________________
>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/cisco-nsp
>> archive at http://puck.nether.net/pipermail/cisco-nsp/
>