Routing Assistance When Ip Routing Is Disabled; Proxy Arp; Default Gateway - Cisco IE-4000 Software Configuration Manual

Configuring IP Unicast Routing
Configuring IP Addressing
EXAMPLE
Switch# configure terminal
Enter configuration commands, one per line.
Switch(config)# interface gi0/2
Switch(config-if)# ip proxy-arp
Switch(config-if)# end

Routing Assistance When IP Routing is Disabled

These mechanisms allow the switch to learn about routes to other networks when it does not have IP routing enabled:

Proxy ARP, page 807

Default Gateway, page 807

ICMP Router Discovery Protocol (IRDP), page 808

Proxy ARP

Proxy ARP, the most common method for learning about other routes, enables an Ethernet host with no routing
information to communicate with hosts on other networks or subnets. The host assumes that all hosts are on the same
local Ethernet and that they can use ARP to learn their MAC addresses. If a switch receives an ARP request for a host
that is not on the same network as the sender, the switch evaluates whether it has the best route to that host. If it does,
it sends an ARP reply packet with its own Ethernet MAC address, and the host that sent the request sends the packet to
the switch, which forwards it to the intended host. Proxy ARP treats all networks as if they are local and performs ARP
requests for every IP address.
Proxy ARP is enabled by default. To enable it after it has been disabled, see
works as long as other routers support it.

Default Gateway

Another method for locating routes is to define a default router or default gateway. All nonlocal 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 switch 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.
DETAILED STEPS
Command
1. configure terminal
2. ip default-gateway ip-address
3. end
4. show ip redirects
5. copy running-config startup-config
Use the no ip default-gateway global configuration command to disable this function.
EXAMPLE
Switch# configure terminal
End with CNTL/Z.
Enabling Proxy ARP, page
Purpose
Enter global configuration mode.
Set up a default gateway (router).
Return to privileged EXEC mode.
Display the address of the default gateway router to verify
the setting.
(Optional) Save your entries in the configuration file.
807
806. Proxy ARP