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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter22 Configuring IP Unicast Routing
Configuring IP Addressing
This is an example of output from the show arp privileged EXEC command.
Switch# show arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.1.2.3 - 0002.4b29.2e00 ARPA GigabitEthernet0/10
Internet 172.20.136.9 120 0030.19c6.54e1 ARPA Vlan1
Internet 172.20.250.42 149 0030.19c6.54e1 ARPA Vlan1
Internet 120.20.30.1 - 0002.4b29.2e00 ARPA Vlan27
Internet 172.20.139.152 101 0030.19c6.54e1 ARPA Vlan1
Internet 172.20.139.130 205 0030.19c6.54e1 ARPA Vlan1
Internet 172.20.141.225 186 0030.19c6.54e1 ARPA Vlan1
Internet 172.20.135.204 169 0002.4b29.4400 ARPA Vlan1
Internet 172.20.135.202 - 0002.4b29.2e00 ARPA Vlan1
Internet 172.20.135.197 172 0002.4b28.ce80 ARPA Vlan1
Internet 172.20.135.196 156 0002.4b28.ce00 ARPA Vlan1
Note For the Catalyst 3550 switch, the output from the show arp privileged EXEC command and the show
ip arp privileged EXEC command are usually the same.
Set ARP Encapsulation
By default, Ethernet ARP encapsulation (represented by the arpa keyword) is enabled on an IP interface.
You can change the encapsulation methods to SNAP if required by your network.
Beginning in privileged EXEC mode, follow these steps to specify the ARP encapsulation type:
To disable an encapsulation type, use the no arp arpa or no arp snap interface configuration command.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Enter interface configuration mode, and specify the Layer 3
interface to configure.
Step3 arp {arpa | snap} Specify the ARP encapsulation method:
arpaAddress Resolution Protocol
snapSubnetwork Address Protocol
Step4 end Return to privileged EXEC mode.
Step5 show interfaces [interface-id] Verify ARP encapsulation configuration on all interfaces or
the specified interface.
Step6 copy running-config startup-config (Optional) Save your entries in the configuration file.