[c-nsp] Load Sharing multihomed BGP with two providers

[Dave Temkin]

In that scenario isn't it going to assume that those other routes are
received via iBGP and generally prefer the routes from that router's
locally connected peer?

-Dave

On Thu, 3 Aug 2006, Scott Granados wrote:

> Why don't you set up a session between router A and router B where you
> basically give each router the other's full view.  Say set up a common
> /30 between them or set the session up over some common network segment
> where both A and B touch.  Use OSPF and the like to distribute your loop
> backs and if you're taking full routes just remove the defaults.
>
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of andrew2 at one.net
> Sent: Thursday, August 03, 2006 11:48 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Load Sharing multihomed BGP with two providers
>
> Trying to figure the best way to accomplish this:
>
> I have two routers each connected to a different provider, each taking
> full routes from their respective providers.  Currently all outbound
> traffic is directed to Router A, so long as it is available and
> announcing itself via IGP.  Router A has a default route that points to
> Router B.  Since the routes learned from Provider A are more specific
> than the default route, currently 99.99% of outbound traffic goes out
> Provider A unless there is a problem with Router A or Provider A.  Which
> is how I wanted it.
>
> Now, however, I'd like to share some the outbound load with Provider B
> on Router B.  I'd like to get the full routes from both providers on
> both routers, turn on bgp multipath and see how things go.  I'm just
> unsure on what the best way to get those routes into the routers is.
> One idea I've been kicking around is to check with both providers and
> see if they'll allow a second BGP session via ebgp multihop sessions.
> In this scenario I'd be sure to inject the next_hop from each provider
> into IGP and limit the max hops so that if the circuit to a provider
> goes down the BGP session doesn't try to establish over the other
> provider's circuit.  Any major gotchas in this scenario?  Is this
> something the big "Tier 1's" typically permit?
>
> Any better way of doing this?  Route Reflector?  iBGP?  Redistributing
> the routes into an IGP seems evil, but technically possible...
>
> Thanks for any pointers,
>
> Andrew
>
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