Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 55)

To limit the number of ARP packets the device will accept each second, enter the rate-limit-arp
command at the global CONFIG level of the CLI.
device(config)# rate-limit-arp 100
This command configures the device to accept up to 100 ARP packets each second. If the device
receives more than 100 ARP packets during a one-second interval, the device drops the additional ARP
packets during the remainder of that one-second interval.
Syntax:[no] rate-limit-arp num
The num parameter specifies the number of ARP packets and can be from 0 through 100. If you specify
0, the device will not accept any ARP packets.
NOTE
If you want to change a previously configured the ARP rate limiting policy, you must remove the
previously configured policy using the no rate-limit-arp command before entering the new policy.
Changing the ARP aging period
When the Layer 3 switch places an entry in the ARP cache, the Layer 3 switch 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no longer valid.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 Layer 3 switches, you can change the ARP age to a value from 0 through 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 globally change the ARP aging parameter to 20 minutes, enter the ip arp-age command.
device(config)# ip arp-age 20
Syntax: ip arp-age num
The num parameter specifies the number of minutes and can be from 0 through 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.
device(config-if-e1000-1/1)# ip arp-age 30
Syntax: [no] ip arp-age num
The num parameter specifies the number of minutes and can be from 0 through 240. The default is the
globally configured value, which is 10 minutes by default. If you specify 0, aging is disabled.
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 subnets, 10.10.10.0/24 and
10.20.20.0/24, 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 10.20.20.69. In standard ARP, a request from a device in the
Changing the ARP aging period
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