Brocade Communications Systems ICX 7250 series, Руководство по настройке

Страница: 25 / 483

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 variable 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ensures that the ARP cache does not retain learned entries that are no longer valid.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.
NOTE
Host devices connected to an ICX 7750 that also have a valid IP address and reply periodically to the arp request are not timed
out, even if no traffic is destined for the device. This behavior is restricted to only ICX 7750 devices.
To globally change the ARP aging parameter to 20 minutes, enter the ip arp-age command.
device(config)# ip arp-age 20
Syntax: [no] ip arp-age num
The num parameter specifies the number of minutes, which 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 the ip arp-age command followed by the new value at
the interface configuration level.
device(config-if-e1000-1/1/1)# ip arp-age 30
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.
Because 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 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.
ARP parameter configuration
Brocade FastIron Layer 3 Routing Configuration Guide
53-1003903-04 25