If your router has multiple serial links all going to routers out on the internet...

StonedHitman

will you need a public ip address for each serial link? I assume so because each interface on a router is in it's own network.

tomtom1

Assuming the links need public subnets assigned to them, yes. You can't have overlapping subnets on different interfaces, unless you get into some complex stuff like VRF's. But in short, yes.