The ARP Table
20-6 IP Configuration
This example shows output from a successful ping to IP address 182.127.63.23:
C5(su)->router#ping 182.127.63.23
182.127.63.23 is alive
Use the traceroute command to display a hop-by-hop path through an IP network from the device
to a specific destination host. Three ICMP probes will be transmitted for each hop between the
source and the traceroute destination. The traceroute command is available in both switch and
routing command modes.
This example shows how to use traceroute to display a round trip path to host 192.141.90.183.
C5(su)->router#traceroute 192.141.90.183
Traceroute to 192.141.90.183, 30 hops max, 40 byte packets
1 10.1.56.1 0.000 ms 0.000 ms 0.000 ms
2 10.1.48.254 10.000 ms 0.000 ms 0.000 ms
3 10.1.0.2 0.000 ms 0.000 ms 0.000 ms
4 192.141.89.17 0.000 ms 0.000 ms 10.000 ms
5 192.141.100.13 0.000 ms 10.000 ms 0.000 ms
6 192.141.100.6 0.000 ms 0.000 ms 10.000 ms
7 192.141.90.183 0.000 ms 0.000 ms 0.000 ms
The ARP Table
Address Resolution Protocol (ARP) is the method for finding a MAC hardware address when only
the IP address is known. The fixed switch firmware allows you to configure Address Resolution
Protocol (ARP) table entries and parameters. ARP is used to associate IP addresses with MAC
addresses. Once determined, the IP address and MAC association is stored in an ARP cache for
rapid retrieval. An IP datagram is then encapsulated into a link-layer frame and sent over the
network.
ARP table entries can be temporary (dynamic) or permanent. A temporary ARP entry has a
timeout interval associated with it. The ARP entry expires at the end of the timeout interval.
You can configure an ARP entry in routing mode or in switch mode. If you set a static route in
router configuration mode, the IP address specified for the static ARP entry must fall within one
of the subnets or networks defined on the routed interfaces of the system. The system can then
match the IP address of the static ARP entry with the appropriate routed interface and associate it
with the correct VLAN.
Refer to the Router Capacities table in the Release Notes for your fixed switch product for a listing
of the number of static ARP entries supported by the product.
•In routing mode, use
–the arp command to configure a permanent static ARP entry. A multicast MAC address
can be used in a static ARP entry.
–the no arp command to remove a static ARP entry.
–the arp timeout command to set the duration in seconds for dynamically learned entries
to remain in the ARP table before expiring. The default value is 14,400 seconds.
–the show ip arp command to display ARP table entries.
–the clear arp-cache command to clear all non-static (dynamic) ARP entries from the ARP
table.
If you don't have routing configured, you can set a static ARP entry using the switch mode
command line.
•In switch mode, use
–the set arp command to add a mapping entry to the switch ARP table.
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