Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 781)

Multi-Service IronWare Switching Configuration Guide 751
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Configuring ARP parameters
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Changing the ARP aging period
When the Brocade device places an entry in the ARP cache, the Brocade device also starts an
aging timer for the entry. The aging timer ensures that the ARP cache does not retain learned
entries that are no longer valid. An entry can become invalid when the device with the MAC address
of the entry is no longer on the network.
The ARP age affects dynamic (learned) entries only, not static entries. The default ARP age is ten
minutes. On the Brocade device, you can change the ARP age to a value from 0 – 240 minutes. If
you set the ARP age to zero, aging is disabled and entries do not age out.
To globally change the ARP aging parameter to 20 minutes, enter the following command.
Brocade(config)# ip arp-age 20
Syntax: [no]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.
To override the globally configured IP ARP age on an individual interface, enter a command such as
the following at the interface configuration level.
Brocade(config-if-e1000-1/1)# ip arp-age 30
Enabling proxy ARP
Proxy ARP allows the Brocade device 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 the Brocade device connected to two subnets,
10.10.10.0/24 and 10.20.20.0/24, the Brocade device can respond to an ARP request from
10.10.10.69 for the MAC address of the device with IP address 10.20.20.69. In standard ARP, a
request from a device in the 10.10.10.0/24 subnet cannot reach a device in the 10.20.20.0
subnet if the subnets are on different network cables, and thus is not answered.
NOTE
An ARP request from one subnet can reach another subnet when both subnets 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.
To enable IP proxy ARP, enter the following command.
Brocade(config)# ip proxy-arp
To again disable IP proxy ARP, enter the following command.
Brocade(config)# no ip proxy-arp
Syntax: [no] ip proxy-arp