Routing Assistance When IP Routing is Disabled These mechanisms allow the device to learn about routes to other networks when it does not have IP routing that is enabled: • Proxy ARP • Default Gateway • ICMP Router Discovery Protocol (IRDP) Proxy ARP Proxy ARP is enabled by default. To enable it after it has been disabled, see the “Enabling Proxy ARP” section. Proxy ARP works as long as other routers support it. Configuring Default Gateway Another method for locating routes is to define a default router or default gateway.
All non-local packets are sent to this router, which either routes them appropriately or sends an IP Control Message Protocol (ICMP) redirect message back, defining which local router the host should use. The device caches the redirect messages and forwards each packet as efficiently as possible. A limitation of this method is that there is no means of detecting when the default router has gone down or is unavailable. To configure default gateway, perform this procedure: Procedure Configuring IP Unicast Routing Routing Assistance When IP Routing is Disabled Command or Action Purpose Step 1 enable Example: Device>enable Enables privileged EXEC mode. Enter your password if prompted.
Step 2 configure terminal Example: Device#configure terminal Enters global configuration mode. Step 3 ip default-gateway ip-address Example: Device(config)#ip default gateway 10.1.5.1 Sets up a default gateway (router). Step 4 end Example: Returns to privileged EXEC mode. Configuring IP Unicast Routing 19