Re: Ebgp Loadbalancing Issue

Hi Eshed,

This is the most complicated scenario, but it can be tuned a little bit to
have some kind of load sharing, perfect load balancing is impossible
though. Check the "bgp bestpath as-path multipath-relax" hidden command,
this will circumvent the need for the AS-Path to be identical for load
sharing to be conducted between routes from different upstream providers
(but still the AS-Path needs to have an identical length), this will tune
your upload traffic, as for your download you'll need to distribute your
advertised prefixes over the two ISPs with redundancy in mind (for example,
advertise subset of more specifics + a prepended summary over one link,
and another summary without prepending over the other). On the other hand
the BGP Link Bandwidth (bgp dmzlink-bw) feature is used for unequal
bandwidth load sharing, and it will affect only the upload traffic (needs
the eBGP sessions to be configured with the directly connected IP
addresses).

Have a nice day.

BR,
Mohammed Mahmoud.

W&#144;W)W W&#144;WWW W <eshedalonie_at_gmail.com> wrote on 8 Apr 2009,
07:56 AM:
Subject: Ebgp Loadbalancing Issue
>Narbik, All
>
> EBGP
> I (R) -----------> ISP1
> B |
> G | EBGP
> P (R) -----------> ISP2
>
>Can I Use Load balancing between ebgp with two routers that connected
>between them with IBGP and the two routers are connected to two Different
>ISP's With Maximum-Paths 2 + DMZ-BWLINK ?
>
>If I Understand correctly
>From Nil website - it says that load balance can only work with one router
>that connects to two other routers in the Same AS.
>And their path calculation should be the same (AS-PATH, LOCAL-PREFERENCE,
>MED)...
>
>http://www.nil.com/ipcorner/LoadBalancingBGP/
>
>Nil Says :
>The only applicability of EBGP load balancing is thus the design where a
>single BGP router has two EBGP sessions into the same autonomous system
>(Figure 4).
>
>
>Can Anyone clarify this ?
>
>Thanks, Eshed.
>
>
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Received on Wed Apr 08 2009 - 09:09:00 ART