Regional AS model
graham at g-rock.net
Thu Mar 24 16:51:06 CDT 2011
Quoting Zaid Ali <zaid at zaidali.com>:
> I have seen age old discussions on single AS vs multiple AS for
> backbone and datacenter design. I am particularly interested in
> operational challenges for running AS per region e.g. one AS for US,
> one EU etc or I have heard folks do one AS per DC. I particularly
> don't see any advantage in doing one AS per region or datacenter
> since most of the reasons I hear is to reduce the iBGP mesh. I
> generally prefer one AS and making use of confederation.
What timing - this is fresh on my mind too as I am in the middle of
doing this myself with three locations, all with independent edges
with different transit providers. I actually do have a private Layer2
circuit between, with one site being in the middle. I only have one
public AS, but I have selected doing the confederation approach (which
some may consider to be overkill with only three edges).
Each site has their own set of IPs and would originate out of their
respective edge, and using EIGRP metric changes at each core to get
0.0.0.0/0 from another edge if the local fails. Each edge is then
announcing each others' subnets with an extra pad or two to keep the
asymmetrical routing down (the private L2 isn't as fast as my transits).
Good luck with your deployment!
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