I'm just going multihome (connected to two providers via BGP). 'Cause I'm the end point there is no need that the updates from the one goes to another. So how to block it i.e.
AS100-------------| AS200------- ME --|
what about this :
neighbor AS200 filter-list 1 out ip as-aspath access-list 1 deny ^100 ip as-aspath access-list 1 permit .*
neighbor AS100 filter-list 1 out ip as-aspath access-list 1 deny ^200 ip as-aspath access-list 1 permit .*
You could probably do it more simple like this:
ip as-path access-list 1 permit ^$
that would permit sending only prefixes with NULL AS-path. (that are the ones that are sourced from your network.
Hi, you could also use communities: On all incoming neighbors use: neighbor External route-map SET-COMMUNITY in
and route-map SET-COMMUNITY permit 10 set community local-AS
That's all. The well known community "local-as" will prevent the so tagged prefixes to leave the local as.
Mathias
raptor schrieb:
Sorry for jumping in ("stealing the thread"?!?), but I have a question related to the above: besides the answer to the original question - how would one properly ballance two providers, from one having a DS3, and from one a T1? ... or is there a method that would let BGP tie - somehow - into line utilization?
Thx, Papi
Is there some reason why you couldn't start a new thread?
BGP doesn't provide any way to do proportional routing, and no routing protocols take load into account (EIGRP has an option for it, but it's not recommended). DS3 is so much faster than T1, I don't see why you would want to use the T1 at all when the DS3 is up, except perhaps to reach customers directly connected to the T1 ISP.
I suggest you have the T1 ISP send you just their customer routes and a default route, and the DS3 ISP send you a default route. Use weights so the DS3 route is preferred when both connections are up. When the DS3 connection dies, you'll fail everything over to the T1 (which will probably cause it to become totally saturated, since I assume your traffic will normally use a significant fraction of the DS3's bandwidth).
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