so if the WAN interface receives an address via DHCP I don't need a default route?

DHCP server will send you a default gateway.

ip route 0.0.0.0 0.0.0.0 Fastethernet0/0

In this case, the router generates an ARP request for each IP address that is not reachable through more specific routes, which practically means that the router generates an ARP request for almost every address on the Internet.

so it is a bad idea to use an interface as my default gateway?

Bad for broadcast networks.

You must use ip-address instead of interface.

[Pls RATE if HELPS]

It's a bad idea, but since it works anyway, most people doesn't realize the ARP havoc until looking into the router like you did.

Thanks for the appreciation and good luck!

Just a small clarification: it is not good to point a static route (especially a static default route) to an interface if the interface is a broadcast type interface which uses ARP. But if the interface is a point to point link (such as HDLC, PPP, or point to point Frame Relay) then it is not bad at all. In fact it is fairly good for the static route to point at point to point interfaces.

HTH

Rick

Hello Paolo,

there is another reason to avoid using this type of static route over a broadcast network: the trick works until someone disables the proxy-arp on the other router's interface.

I saw this on a production network some years ago.

Best Regards

Giuseppe