[c-nsp] BGP Routing Failover for multiple classes of customers

[Gert Doering]

Hi,

On Tue, Sep 06, 2005 at 10:19:17PM -0700, Richard J. Sears wrote:
> Customer 1 we would like to only get to provider_1 (this works)

Unless you do VRF things, this will only "work" for certain definitions
of "work".

The main problem is the BGP decision process - you cannot have two
best path routes in your system, so the router will pick one, and then
evaluate whether to send this route to its peers (= your customers).

If for a given prefix, like "4.0.0.0/8", your router selects provider_2
as "best path", your customer 1 will *not* receive "4.0.0.0/8 via 
provider_1", but "no route to 4.0.0.0/8 at all".

So customer 1 isn't getting a full BGP table "via provider_1", but
just those prefixes that happen to have a best path via provider_1, 
which almost all the time will be a very much incomplete BGP table.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
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