We're currently running a configuration that uses an IP address on the FastEthernet port, ip unnumbered on the Serial pointing to FE0/0, and OSPF. It works well but I am aware of the problems involved if we lose the FE connection so I am planning to move to a loopback interface.
Which should be simple enough, but I'm not positive of what I can get away with. The obvious setup I came up with was: R1: FE0/0: 10.1.1.254/24 Loopback0: 10.10.1.1/30 Serial: ip unnumbered Loopback0 R2: FE0/0: 10.1.2.254/24 Loopback0: 10.10.1.5/30 Serial: ip unnumbered Loopback0
But the question that came up was whether, instead, I could use
10.10.1.1/30 and 10.10.1.2/30 on Loopback0, or to put it another way, can the two be on the same subnet?Then I wondered, could I use a single address for the whole router, in other words: R1: Loopback0: 10.1.1.254/24 Serial: ip unnumbered Loopback0 FE0/0: ip unnumbered Loopback0 R2: Loopback0: 10.1.2.254/24 Serial: ip unnumbered Loopback0 FE0/0: ip unnumbered Loopback0
Or is that too simple?