Configuring IP
December 2005 © Foundry Networks, Inc. 16 - 5
The software can learn an entry when the Layer 2 Switch or Layer 3 Switch receives an ARP request from another
IP forwarding device or an ARP reply. Here is an example of a dynamic entry:
Each entry contains the destination device’s IP address and MAC address.
Static ARP Table
In addition to the ARP cache, Layer 3 Switches have a static ARP table. Entries in the static ARP table are user-
configured. You can add entries to the static ARP table regardless of whether the device the entry is for is
connected to the Layer 3 Switch.
NOTE: The Layer 3 Switches have a static ARP table but Layer 2 Switches do not.
The software places an entry from the static ARP table into the ARP cache when the entry’s interface comes up.
Here is an example of a static ARP entry:
Index IP Address MAC Address Port
1 207.95.6.111 0800.093b.d210 1/1
Each entry lists the information you specified when you created the entry.
To display ARP entries, see the following:
• “Displaying the ARP Cache” on page 16-64 – Layer 3 Switch
• “Displaying the Static ARP Table” on page 16-65 – Layer 3 Switch only
• “Displaying ARP Entries” on page 16-75 – Layer 2 Switch
To configure other ARP parameters, see the following:
• “Configuring ARP Parameters” on page 16-25 – Layer 3 Switch only
To increase the size of the ARP cache and static ARP table, see the following:
• For dynamic entries, see the section “Displaying and Modifying System Parameter Default Settings” on
page 4-8. The ip-arp parameter controls the ARP cache size.
• Static entries, “Changing the Maximum Number of Entries the Static ARP Table Can Hold” on page 16-28 –
Layer 3 Switches only. The ip-static-arp parameter controls the static ARP table size.
IP Route Table
The IP route table contains paths to IP destinations.
NOTE: Layer 2 Switches do not have an IP route table. A Layer 2 Switch sends all packets addressed to another
sub-net to the default gateway, which you specify when you configure the basic IP information on the Layer 2
Switch.
The IP route table can receive the paths from the following sources:
• A directly-connected destination, which means there are no router hops to the destination
• A static IP route, which is a user-configured route
• A route learned through RIP
• A route learned through OSPF
• A route learned through BGP4
The IP route table contains the best path to a destination.
• When the software receives paths from more than one of the sources listed above, the software compares the
IP Address MAC Address Type Age Port
1 207.95.6.102 0800.5afc.ea21 Dynamic 0 6
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