Foundry Networks Switch and Router Installation And Configuration Manual page 473

The ARP age affects dynamic (learned) entries only, not static entries. The default ARP age is ten minutes. On
Layer 3 Switches, you can change the ARP age to a value from 0 – 240 minutes. You cannot change the ARP
age on Layer 2 Switches. If you set the ARP age to zero, aging is disabled and entries do not age out.
To change the ARP age on a Layer 3 Switch, use either of the following methods.
USING THE CLI
To modify the ARP aging parameter to 20 minutes, enter the following command:
BigIron(config)# ip arp-age 20
Syntax: ip arp-age <num>
The <num> parameter specifies the number of minutes and can be from 0 – 240. The default is 10. If you specify
0, aging is disabled.
USING THE WEB MANAGEMENT INTERFACE
1. Log on to the device using a valid user name and password for read-write access. The System configuration
panel is displayed.
2. Click on the plus sign next to Configure in the tree view to display the list of configuration options.
3. Click on the plus sign next to IP to display the list of IP configuration options.
4. Select the General link to display the IP configuration panel.
5. Enter a value from 0 – 240 into the ARP Age field.
6. Click the Apply button to save the change to the device's running-config file.
7. Select the Save link at the bottom of the dialog. Select Yes when prompted to save the configuration change
to the startup-config file on the device's flash memory.
Enabling Proxy ARP
Proxy ARP allows a Layer 3 Switch to answer ARP requests from devices on one network on behalf of devices in
another network. Since ARP requests are MAC-layer broadcasts, they reach only the devices that are directly
connected to the sender of the ARP request. Thus, ARP requests do not cross routers.
For example, if Proxy ARP is enabled on a Layer 3 Switch connected to two sub-nets, 10.10.10.0/24 and
20.20.20.0/24, the Layer 3 Switch can respond to an ARP request from 10.10.10.69 for the MAC address of the
device with IP address 20.20.20.69. In standard ARP, a request from a device in the 10.10.10.0/24 sub-net
cannot reach a device in the 20.20.20.0 sub-net if the sub-nets are on different network cables, and thus is not
answered.
NOTE: An ARP request from one sub-net can reach another sub-net when both sub-nets are on the same
physical segment (Ethernet cable), since MAC-layer broadcasts reach all the devices on the segment.
Proxy ARP is disabled by default on Foundry Layer 3 Switches. The feature is not supported on Foundry Layer 2
Switches.
To enable Proxy ARP, use either of the following methods.
USING THE CLI
To enable IP proxy ARP, enter the following command:
BigIron(config)# ip proxy-arp
To again disable IP proxy ARP, enter the following command:
BigIron(config)# no ip proxy-arp
Syntax: [no] ip proxy-arp
December 2000
Configuring IP
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