Splitting ARIN assignment

Thu May 22 17:45:47 UTC 2008

I I were you, I will advertise as following.

/21 Original ARIN allocation
/22 First half of ARIN allocation
/22 second half of ARIN allocation

In this case, you will have backup /21 route just in case of filtering
or something like that.
But in normal case, traffic will be routed based on more specific
routes, which are /22s.

In some case, upstream ISPs may filter based on strict filtering, which
means all BGP prefix announcement should be matched with registered CIDR
info including subnet size.
In most case, upstream ISP will accept any subnet size between
registered size (/21) and /24 size.

Because of load sharing and traffic engineering requirement, it is easy
to handle those situation with /22 size.

Make sure that your two location is inter-connected directly, and have
enough capacity when each of location upstream connection goes down.

Hyun

ames Kelty wrote:
> Hey all,
>
> I'm looking for an opinion from the group. I have an ARIN /21
> assignment and a new requirement for a second data center. Rather than
> ask for another assignment, I would like to advertise one /22 from one
> location and the other /22 from the second location both with the same
> asn. My apps will work that way, so I don't have an issue internally,
> but I'm looking for a broader base opinion on that.
>
> Thanks a lot!
>
> -James
>
>
>
>