OSPF router ID

Quency

I have a question about OSPF router ID here. Anyone could help me?
Question: What factor determines the OSPF router ID? the highest IP address of any logical interface or physical interface (assmume both interfaces are configured) ? lookback interface is logical interface? subinterface is logical interface? I am confused by these concepts.

Thanks for your help.

kplab

OSPF chooses the highest IP address among all loopback interfaces as the RID. If no loopback interface is present, the highest IP address among the physical interfaces is chosen.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfospf.htm#wp1001369

Yankee

And don't forget that if for some reason that address is removed OSPF will not forget it without a router reload.

Yankee

Nocturnal

You have logical interfaces and hardware interfaces. Hardware is an actual piece of hardware, like a serial interface. Sub-interfaces are logical interfaces. A loopback interface is logical because it doesn't refer to a piece of hardware. A multilink interface is logical. The thing you plug a cable into is hardware...physical. Logical is a software representation. Even though you plug a cable into a serial interface with three logical interfaces, the logical interfaces are defined in software and aren't the actual piece of hardware, so they are logical. That's how I understand it. Correct me if I'm wrong.