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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 22 Configuring IP Unicast Routing
Configuring IP Addressing
You can perform these tasks to configure address resolution:
•
Define a Static ARP Cache, page 22-11
•
Set ARP Encapsulation, page 22-12
•
Enable Proxy ARP, page 22-13
Define a Static ARP Cache
ARP and other address resolution protocols provide dynamic mapping between IP addresses and MAC
addresses. Because most hosts support dynamic address resolution, you usually do not need to specify
static ARP cache entries. If you must define a static ARP cache entry, you can do so globally, which
installs a permanent entry in the ARP cache that the switch uses to translate IP addresses into MAC
addresses. Optionally, you can also specify that the switch respond to ARP requests as if it were the
owner of the specified IP address. If you do not want the ARP entry to be permanent, you can specify a
timeout period for the ARP entry.
Beginning in privileged EXEC mode, follow these steps to provide static mapping between IP addresses
and MAC addresses:
To remove an entry from the ARP cache, use the no arp ip-address hardware-address type global
configuration command. To remove all nonstatic entries from the ARP cache, use the clear arp-cache
privileged EXEC command.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
arp ip-address hardware-address type
Globally associate an IP address with a MAC (hardware) address
in the ARP cache, and specify encapsulation type as one of
these:
•
arpa—ARP encapsulation for Ethernet interfaces
•
snap—Subnetwork Address Protocol encapsulation for
Token Ring and FDDI interfaces
•
sap—HP’s ARP type
Step 3
arp ip-address hardware-address type [alias]
(Optional) Specify that the switch respond to ARP requests as if
it were the owner of the specified IP address.
Step 4
interface interface-id
Enter interface configuration mode, and specify the interface to
configure.
Step 5
arp timeout seconds
(Optional) Set the length of time an ARP cache entry will stay in
the cache. The default is 14400 seconds (4 hours). The range is
0 to 2147483 seconds.
Step 6
end
Return to privileged EXEC mode.
Step 7
show interfaces [interface-id]
Verify the type of ARP and the timeout value used on all
interfaces or a specific interface.
Step 8
show arp
or
show ip arp
View the contents of the ARP cache.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
