Re: The IESG Approved the Expansion of the AS Number Registry

* Chris L. Morrow:

...

| 6. Transition | | The scheme described in this document allows a gradual transition | from 2-octet AS numbers to 4-octet AS numbers. One can upgrade one | Autonomous System or one BGP speaker at a time.

Routers on stub ASs don't need upgrading at all, for instance.

but filter lists and such I imagine might :(

Only if you want to keep your fine-grained filters, which shouldn't be a problem over the next few years. From a purely BGP 4 perspective, the transition looks like a new tier 1 ISP entering the stage. (But if more than one of your peers switch, you better upgrade as well.)