From: Joe Chang (changjoe@earthlink.net)
Date: Thu Mar 13 2003 - 19:51:26 GMT-3
I couldn't find anything directly related to this issue in the RFCs.
Allowing multiple paths to EBGP routes can be acheived simply by setting the
"maximum-paths" value under the routing process (the default value is 1 for
BGP). Why it is assumed that a multihomed AS should "prejudice" the routes
it advertises to it's secondary provider may have to do more with economic
than technical considerations.
----- Original Message -----
From: "Anthony Pace" <anthonypace@fastmail.fm>
To: <ccielab@groupstudy.com>
Sent: Thursday, March 13, 2003 2:43 PM
Subject: BGP load balancing (via best path)
> All of the implementations I have seen, (as well as the examples in
> Halabi's book) use a Primary/Failover method for both INGRESS and EGRESS
> traffic when BGP is used. Outbound advertisements with AS-PREPEND'S to
> the backup to cause the "world" to come in via the Primary; and perhaps
> better local preference for routes learned on the PRimary to cause our
> outbound traffic to use the primary.
>
> There are many flavors of this,but the principle remains consistant. For
> any given route a primary and a failover.
>
> Here is my question:
>
> What is the detriment of taking in the all BGP routes from 2 providers
> and choosing the best path for outbound traffic; What is the detriment of
> advertising my own address space to 2 providers with no PREPENDS. Just
> let the traffic come in and go out based on the "end systems" proximity
> to either of my 2 providers?
>
> Without AS-PREPENDS to the BACKUP provider, I understand that if the
> PRIMARY provider gave me a block of their address space, I would wind up
> seeing the traffic all come in via the BACKUP link (as the backup
> provider would advertise a more specific, route and the PRIMARY would
> summarize my space into an aggrigate)
>
> Does that sound correct?
>
> If the address space belonged to neither provider, then couldn't I just
> advertise it to both and let the traffic find me through both?
>
> Am I overlooking something very obvious?
>
> Anthony Pace CCIE#10349
>
>
> --
> Anthony Pace
> anthonypace@fastmail.fm
>
> --
> http://www.fastmail.fm - One of many happy users:
> http://www.fastmail.fm/docs/quotes.html
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