38-12
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
OL-12247-04
Chapter 38 Configuring IP Unicast Routing
Configuring IP Addressing
Enable Proxy ARP
By default, the switch uses proxy ARP to help hosts learn MAC addresses of hosts on other networks or
subnets.
Beginning in privileged EXEC mode, follow these steps to enable proxy ARP if it has been disabled:
To disable proxy ARP on the interface, use the
no ip proxy-arp
interface configuration command.
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:
•
•
•
ICMP Router Discovery Protocol (IRDP), page 38-13
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. The host that sent the request then 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 the
. Proxy ARP 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 returns an IP Control Message Protocol
(ICMP) redirect message, identifying the local router that the host should use. The switch caches the
redirect messages and forwards each packet as efficiently as possible. This method cannot detect when
the default router has failed or is unavailable.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface
interface-id
Enter interface configuration mode, and specify the Layer 3
interface to configure.
Step 3
ip proxy-arp
Enable proxy ARP on the interface.
Step 4
end
Return to privileged EXEC mode.
Step 5
show ip interface
[
interface-id
]
Verify the configuration on the interface or all interfaces.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
