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