IP Broadcast Settings
Fixed Switch Configuration Guide 20-7
–the clear arp command to delete a specific entry or all entries from the switch ARP table.
–the show arp command to display the link level ARP table.
Proxy ARP
This variation of the ARP protocol allows the router to send an ARP response on behalf of an end
node to the requesting host. Proxy ARP can be used to resolve routing issues on end stations that
are unable to route in the subnetted environment. The fixed switch will answer to ARP requests
on behalf of targeted end stations on neighboring networks.
Proxy ARP is disabled by default and can be enabled per interface with the ip proxy-arp
command in router interface configuration mode.
ARP Configuration
Procedure 20-4 on page 20-7 lists the commands used to configure the ARP table in router
configuration mode.
Refer to the CLI Reference for your platform for details about using the commands listed above.
The following example sets a static ARP entry in routing configuration mode, then displays the
ARP table.
C5(su)->router(Config)#arp 134.141.235.165 0002.1664.a5b3
C5(su)->router(Config)#show ip arp
Protocol Address Age (min) Hardware Addr Interface
------------------------------------------------------------------------------
Internet 134.141.235.251 0 0003.4712.7a99 Vlan1
Internet 134.141.235.165 - 0002.1664.a5b3 Vlan1
Internet 134.141.235.167 4 00d0.cf00.4b74 Vlan2
IP Broadcast Settings
Directed Broadcast
Directed broadcast is an efficient mechanism for communicating with multiple hosts on a network
while only transmitting a single datagram. A directed broadcast is a packet sent to all hosts on a
Procedure 20-4 Configuring the ARP Table
Step Task Command(s)
1. In router global configuration mode, add static
entries to the ARP table.
arp ip-address mac-address
2. Optionally, in global configuration mode, change
the duration that dynamic ARP entries will stay
in the ARP table before expiring.
arp timeout seconds
3. Optionally, in router interface configuration
mode, enable Proxy ARP on an interface.
ip proxy-arp
4. In any router mode, display the ARP table. show ip arp [ip-address]|[vlan vlan-
id]|[output-modifier]
5. Optionally, clear the ARP cache. clear arp cache
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