From: Huan Pham (huan.pham@valuenet.com.au)
Date: Fri Mar 28 2008 - 08:58:09 ART
Hi Geert,
How about these three options:
Option1:
--------
Keep local prefences, AS path, Origin, MED for prefixes advertised by Site A
& B the same. Tweak the IGP to make Site1 closer to SiteA, and Site2 closer
to SiteB.
http://www.cisco.com/warp/public/459/25.shtml
"Prefer the path with the lowest IGP metric to the BGP next hop.
Continue, even if bestpath is already selected."
Option2:
--------
Use community to change the Local Preference.
Set routes advertised by siteA with community A & routes advertised by Site
B with community B. On Site 1 and all the intermediate sites from Site1 to
Site A, set a higher Local Preference for prefixes with community A.
Similarly On Site 2 and all the intermediate sites from Site2 to Site B, set
a higher Local Preference for prefixes with community B.
If you only manipulate Local Preference on site1 and site 2, you may get a
routing loop, if the intermediate sites do not agree on where to best route
traffic out.
Option3:
--------
Divide your AS into Confederations, where site 1 and SiteA belong to one
Confederation, and Site2 and Site B belong to another. You can then further
tweak best route selection within a confederation using Local Preference.
Cheers,
Huan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Geert Nijs
Sent: Friday, 28 March 2008 8:43 PM
To: ccielab@groupstudy.com
Subject: BGP Question
All,
Suppose i have one large BGP AS system with 10 sites (ie AS 65000) and two
main sites insert the same prefixes (ie. SITE_A and SITE_B).
I want to have some sort of predetermined load-balancing:
ie. SITE_1 chooses SITE_A as exit point to get to the prefixes.
however SITE_2 needs to choose SITE_B as exit point to get to the prefixes.
All are running in the same AS 65000
What are my options ?
Geert
#CCIE13729
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