odd BGP Problem

Gary · Guest

We have a router connected to 2 x tier1 provider routers over a single
x-connect and we run BGP to them no problems. We have taken on a new client
that wants their own dedicated cable and BGP session to the same 2 routers
and a second x-connect is now in and 2 new BGP sessions are up to what are
actually the same tier1 routers.

The client wants his address space routed over his cable to the tier1
provider unless that cable fails in which case the traffic should failover
to our x-connect to the tier1 provider.

The question is how do I get the customers traffic to ONLY leave via his
x-connect cable/BGP sessions while it is up but failover to ours if his
fails. Also how do I get the inbound traffic to ONLY come down one set of
BGP sessions (the clients) as opposed to our BGP sessions while his are up.

An ASCI Diagram would look like

Our Router A x------------our x-connect------------------------x Tier1
Router A & B - This carries to BGP sessions on a small subnet which we use
for clients to transit generally
Our Router A x------------client x-connect----------------------x Tier 1
Router A & B- This should only carry client subnet in and out while up
otherwise failover to our cable and BGP sessions

Both cables carry 2 BGP peering sessions receivong full routing tables with
both Tier1 Router A and B so in total we now gave 4 full routing tables form
the same Tier1 provider on Our Router A.

Hope this makes sense.
Thanks
Gary

Barry Margolin · Guest

In article <%6Luj.3489$0M3.833@newsfe17.lga>,
"Gary" <gshine@netlink.info> wrote:

Yandy Ramirez · Guest

Well having the customer with a separate x-connect and bgp sessions directly
to the Transit providers should automatically have a shorter as-path from
cust-to-provider. But the customer can set a higher local-pref on the routes
received from those two neighbors and a lower local-pref to the prefixes
received from you.

Now controlling inbound traffic is a bit trickier you can try AS-PREPEND
(even though technically it should route automatically to his direct
connection) but that's beyond your control as the providers can set
LOCAL-PREF on their side and their goes that idea. So what you can really do
is.

1) BGP conditional advertisement (where you track a certain prefix) maybe a
loopback on the customer routers (2 in this case) and only advertise the
customers prefixes to the providers through your link if and only if both
loopbacks go down. That way the provider will really only see the customers
prefixes through their link unless it goes down, then you start advertising
The customers prefixes through your connection.

cya

On 2/19/08 11:51 PM, in article
barmar-D1A4BA.23512119022008@comcast.dca.giganews.com, "Barry Margolin"
<barmar@alum.mit.edu> wrote: