RE: [isp-bgp] BGP Multihoming tips

["Darrell Hyde" <DHyde@...>]

This sounds like a pretty vanilla setup. Your first step should be to
contact ISP2 and check what their requirements are for allowing their
downstream peers to announce provider address space. Some require that
the ISP assigning the space SWIP the space to you, some require a letter
of authorization from the assigning provider, some don't care.

For inbound load-sharing, you should contact each of your ISPs to find
out what means they support for adjusting the local pref of routes you
announce to them. Most have communities that you can tag  your routes
with to affect this. That way you have some control over what inbound
path your routes take.

For outbound load-sharing, there are lot of options. Possibly the
simplest is to just use route-maps to adjust local pref of routes based
on their AS path or other attributes. On the other side of the spectrum
of complexity is Cisco OER (optimized edge routing). OER allows your
routers to make intelligent decisions about routing based on non-BGP
aware variables such as link utilization, throughput, and packet-loss. A
simple OER setup for example, would allow you to set the utilization
threshold on each of your links to say...50%. Once setup, OER would
dynamically adjust BGP local pref to keep each of you links within
threshold by moving flows between routers. In addition OER can be
configured to detect upstream peering problems and select a more optimal
exit link for the top X prefixes being affected.

The technology is really cool, but definitely still somewhat in its
infantile stages. I'd recommend opening a case with TAC to determine
what IOS version would be best for your deployment. 12.4 mainline seems
to be the best bet these days for stability.

- Darrell

> -----Original Message-----
> From: Praful Jaded [mailto:praful_jd@...] 
> Sent: Friday, May 13, 2005 3:17 PM
> To: isp-bgp@isp-bgp.com
> Subject: [isp-bgp] BGP Multihoming tips
> 
> Hi All,
> 
> I currently have to setup a network involving BGP
> multihoming to two different ISPs. I have a /24 IP
> space from ISP1 now.I would like to use it for my
> network involving DMZ.I have two Cisco 7200 routers
> which will run IBGP between them and the ISP1
> terminates on R1 and ISP2 on R2 running EBGP. I want
> to have inbound and outbound traffic load shared
> between the ISPs and redundancy when one ISP fails.
> Suggest me some good BGP multihoming tuning tips and
> what do I need to negotiate with my ISPs for better
> reachability of my network in the internet ?
> 
> Since I have the PA ( Provider Assigned)  /24 space
> from ISP1 , how do I go forward with ISP2 to advertise
> it . The two ISPs are peered directly.
> 
> Thank You
> Praful
> 
> 
> 
> 	
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