>This may take some explaining, so just bear with me. Also keep in mind that
>I've been having hardly any time to read Halabi's BGP book, but will
>probably go read some after this.
>
>We're connected to a few ISPs which allow BGP peering (which I should be
>settings up sometime soon).
I need to get clarification here. There are two meanings of the term
"peer" in the BGP context, the first being a simple establishment of
any BGP relationships, and the second being an economic relationship
of equals, where you exchange customer routes without financial
compensation. The alternative to the second is to buy transit from
an upstream ISP.
>We've also got two ISPs that will not peer, nor
>exchange customer routes with us. One is a free 1.5mbit SDSL connection as
>we're one of their VARs, the other is a lame T1 that we're stuck in a 3 year
>contract for a bit more.
>
>Right now, I just use static routes to send traffic out the SDSL connection
>as the provider only has a single class B. For the T1 to a much larger
>provider with address space all over, it's just not worth it to try and do
>much with it...
I don't understand what you mean by address space all over, or not
being worth it. Sometimes the whole motivation for BGP is to
exchange very specific and extensive address information with
adjacent AS, at the same time avoiding leaking large numbers of
irrelevant routes into the global routing system.
>
>Anyway, here is the thought: I happen to know the admins a at number of
>other ISPs that are connected to the T1 and some other sites that have SDSL
>access to the same provider as us.
>
>The catch is that of course we could set static routes out to these ISPs,
>but it's somewhat risky, especially with the SDSL as even though the
>ethernet interface it's connected to may still be up, the SDSL line itself,
>or perhaps something along the SDSL provider's backbone might be down
>between us and another of the SDSL customers, but the static routes to the
>SDSL link would stay up as the interface is still up. Same is true with the
>T1.
I don't think there's any way you can know there is a reachability
failure in a non-directly-connected link without running a routing
protocol. In the case of an ISP, that pretty well has to be BGP.
>
>Since neither of these ISPs will peer with us, could we still establish some
>routing protocol with the smaller ISPs like us that are connected off of
>them and want to transit traffic through these lesser used links.
Why not BGP to the smaller ISPs? There might be a need to coordinate
private AS numbers.
Remember that the BGP tunnels can be between loopback interfaces, so
as long as you can reach the loopback in the other AS, and
appropriately set ebgp multihop, you should be able to run a session
without the intervening ISP being aware of it. Can't promise what
the performance would be.
>Otherwise, the netblocks we have would route traffic back through the ISPs
>they belong to or that we're announcing them with BGP on.
>
>The biggest thing is that it needs to be dynamic. If the route over the
>common single upstream ISP is down, but the connections to these ISPs are
>up, routes out to our defaults/BGP peers might still get us connected.
>
>Thoughts? Comments? Am I just nuts?
>
>--
>Jason Roysdon, CCNP+Security/CCDP, MCSE, CNA, Network+, A+
>List email: [EMAIL PROTECTED]
>Homepage: http://jason.artoo.net/
>Cisco resources: http://r2cisco.artoo.net/
>
>
>
>
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