Re:[isp-bgp] isp-bgp digest: December 06, 2004

[FeatureBug <featurebug@...>]

Hi
  Load balancing in round-robin fashion will only be
possible with both links to a single AS. Other-wise
you will never achieve 50-50 load balancing. In your
case we have two different AS'es advertising your more
specific network prefix, and assuming shortest AS path
routing, incoming traffic may take either of your
upstream ISPs based on where it came from. 
Even for traffic coming in from another upstream AS
directly connected to both your ISPs, shortest path
IGP routing within that AS may dictate which BGP
speaker traffic will exit from,  and hence which ISP
it will choose downstream, on the way to your network.


For outgoing traffic even if your router has equal
destination prefixes from both AS'es advertised into
your network, then your BGP speaker will chooses a
single path based on router ID or peer. When multipath
is enabled both EBGP paths need to be learned from the
same AS - this is not the case here. 

So routing will always be asymmetric and not entirely
in your control. 

You can try adding two static default routes in your
routing table which will load balance your outgoing
traffic - instead of receiving updates from your ISP.
But incoming traffic will still be influenced upstream
and you can have no control over it. 

So like Kerwin below put simply - both links will have
to be into same AS.

Best Regards
Rahul Sawarkar


--- ISP-BGP Discussion List digest
<isp-bgp@...> wrote:

> ISP-BGP Digest for Monday, December 06, 2004.
> 
> 1. Re: load balancing with EBGP
> 
>
----------------------------------------------------------------------
> 
> Subject: Re: load balancing with EBGP
> From: kerwin m <anaconda.m@...>
> Date: Thu, 2 Dec 2004 03:27:40 -0800
> X-Message-Number: 1
> 
> It is possible if the peer you are peering with is
> the same (Upstream Provi=
> der)
> The BGP Multipath command should work.
> 
> 
> On Sun, 21 Nov 2004 21:15:05 -0800 (PST), suraj
> <suraj_rt@...> wrote:
> > Hi,
> >=20
> > Please provide me the solution to the following
> > problem;
> >=20
> > Protocol running :BGP
> > Scenario: We have a single router where two
> different
> > links of that router are terminated with two
> differnt
> > service providers.These links are used for
> internet to
> > ours users sitting in our Lan.Is it possible to
> make
> > utilize these two links simultaniously( Is it
> posible
> > to load balance these two links using the BGP,I
> > believe Load balancing is not possible with BGP as
> BGP
> > takes the best path).PLease let me know whether is
> > there any other way to acheive load sharing/load
> > balancing with BGP?
> >=20
> > Suraj
> > Consultant
> > ACC technologies
> >=20
> > __________________________________
> > Do you Yahoo!?
> > The all-new My Yahoo! - Get yours free!
> > http://my.yahoo.com
> >=20

> =07 ______________


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> 
> --=20
> T & R
> Kerwin
> 
> 
> 
> ---
> 
> END OF DIGEST
> 
>        
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