I am planning to migrate an /22 Subnet into a other datacenter. Currently i have announced every /24er seperatly.

My plan is, that i create a /22 subnet with the AS from the new datacenter on ripe. After i have migrated a /24 block i unannounce that /24 announcement and migrate the next ip block.

Does i understand it correctly, that when i stop the announcement of the /24 subnet, it will fall back to the less specific announcement and the IPs will be routed into the new datacenter?

  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 7 '17 at 19:34

You can use aggregate routes, and announce only those, or you can announce the aggregate and individual routes. As long a one of the individual routes in an aggregate are in your routing table, the aggregate route will be announced.

Creating an aggregate route will also create a route to Null0, so that any traffic coming in for that aggregate which doesn't match any of the individual routes, will be dropped.

Simply announcing a less specific route, rather than using an aggregate will not work, unless you have the aggregate route in your routing table, since BGP only announces routes to which it has a path.

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