Noob Question On IP default-gateway

The ip default-gateway command differs from the other two commands. It should only be used when ip routing is disabled on the Cisco router.

I dont understand the above statement. I thought that all routers have to do routing? All routers interface have to be assigned an ip address for routing.

Why should someone disable ip routing? Doesnt it defeat the purpose of a router?
What is ip routing anyway?

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NetworkVeteran

hitmen wrote: »

I thought that all routers have to do routing?

Now you know better. IOS can be used to do bridging/switching instead of routing if one prefers. While it's customary for a router to do routing, its by no means mandatory. Cisco doesn't force you to do anything.

All routers interface have to be assigned an ip address for routing. Doesnt (no ip routing) defeat the purpose of a router?

Completely false. I have a router in front of me with "no ip routing" configured, and it's doing a great job routing IPv6 traffic. Without changing that configuration, it could similarly route IPX or CLNS traffic. Remember, IPv4 is not the only L3 protocol.

What is ip routing anyway?

I've covered the nuance of the "ip" (IPv4) bit at the beginning of that line. As for what routing in general is, I will say bridging is a L2 process and routing is a L3 process. Beyond that, I'll defer to Google or your textbook's explanation.

CodeBlox

I had a case where I disabled routing on a voice router at work and assigned it a default gateway since it's not to participate in routing (Doesn't have any routing protocols or static routes configured).