Just wanted to commend Brian on an excellent explanation.
Whenever you start studying BGP (and advanced interior routing), and
things start getting confused, it's a good idea always to stop and
think:
am I dealing with TRAFFIC flow or ROUTING UPDATE flow?
>On Sat, 9 Dec 2000, Jennifer Mellone wrote:
>
>> BGP Local Pref is used to control outbound traffic. MED/Metric is used to
>> control inbound traffic. Why is it that you do an inbound route map (vs
>> outbound) when setting local pref and an outbound route map (vs. inbound)
>> when setting MED? It seems opposite.
>
>ok.......here we go:
>
>to get OUT of a router you follow one of the routes in the routing table.
>These routes come IN to the router from say a peer or upstream. So you
>need to modify them as they come IN so that they are changed before they
>are added to the routing/bgp table. Inbound routes effect outbound
>traffic.
>
>for traffic to get IN to your router, its going to follow one of the
>routes that came OUT of your router. Your router announces its routes to
>its BGP peers. On their way out you can modify these routes, such as
>setting med etc. Outbound routes effect inbound traffic.
>
>
>For local pref:
>
>1. route comes from our peer into your router
>2. your router can set the local pref of this route coming into your
>router
>3. your router adds this route to its bgp/routing tables
>
>now your router will use this route for outbound traffic.
>
>For MED:
>
>1. a route is in your router
>2. you announce this route to a BGP peer
>3. on its way out to the peer, you can modify the metric (MED)
>4. The route is added to the peers routing/bgp tables
>5. the peer may use this route to get traffic into you
>
>Brian
>
>
>>
>> - Jennifer Mellone
>>
>> _________________________________
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>
>-----------------------------------------------
>Brian Feeny, CCNP+ATM, CCDP [EMAIL PROTECTED]
>Network Administrator
>ShreveNet Inc. (ASN 11881)
>
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