We've seen forced renumbering already being done. I'll defer my remarks on whether this is good or bad. Thinking of scaling in the future why does the old ISP want the administrative burden of configuring "unreachable" and then offer the computational burden to the entire Internet of a "unclean" CIDR block. And the new ISP putting a standalone network number which needs to be computed upon. CIDR seems like a future lose-lose situation unless the blocks are clean. And the larger the blocks the bigger win. These should be the goals for the future. "Strongly urge" seems like the cows are out of the barn already for us old dirt farmers. Marty
If a component moves, and does not want to renumber, the old provider should announce an unreachable for the component (that is obviously more specific than the aggregate) and the new provider should announce the component that moved.
You should ask the customer to renumber and explain why and strongly urge then to do so. I don't think anyone is advocating forced renumbering (are they)?
Curtis