[j-nsp] eBGP with internet provider from DataCenters

[Dave Curado]

Hi Yham,

On the Pro side, you would conserve one ASN by using the same ASN for 
both data centers.
Also, if in the future the datacenters were to get some direct 
connectivity with each other, it
would be relatively straight forward to join the network control planes 
together.
I can't think of any other Pros, but perhaps there are some.

On the Con side, each data center would hear about the other's network 
blocks via bgp
advertisements to/from your providers. By default, each data center's 
peering routers would
not learn the routes from the other data center, as their own ASN would 
appear in the AS path.
The result: each data center would not have routes for the other.

There is a way to override that, by configuring the BGP sessions with a 
"allow one AS loop"
sort of syntax.  (I know JUNOS allows this for L3VPNs using BGP as the 
CE-PE protocol, so
I suspect Cisco does too.)  Or, you could do something with static routes.
There are probably several other solutions to this problem.

While I'm all for conserving ASN resources, I think that having each 
datacenter have its
own ASN is the cleaner way to do things.  But that's just IMHO.

HTHs,
Dave


On 11/15/13 8:18 AM, Yham wrote:
> Hi Guys,
>
> If we have two active/active DataCenters on different geographical
> locations and going to peer with the same provider for internet. What are
> the pros and cons of having same Autonomous Number on both data centers. In
> other word which is more scalable and practical, having both data cernter
> on single public ASN or should be two different when peering with same
> internet providers. Can you please share you thoughts on it.
>
> Regards
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