Dell PowerConnect B-RX Configuration Manual page 261

Enabling proxy ARP
Proxy ARP allows the 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 device connected to two subnets, 10.10.10.0/24 and
20.20.20.0/24, the device 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 subnet cannot reach a device in the 20.20.20.0 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.
BigIron RX(config)# ip proxy-arp
To again disable IP proxy ARP, enter the following command.
BigIron RX(config)# no ip proxy-arp
Syntax: [no] ip proxy-arp
Creating static ARP entries
The device has a static ARP table, in addition to the regular ARP cache. The static ARP table
contains entries that you configure.
Static entries are useful in cases where you want to pre-configure an entry for a device that is not
connected to the device, or you want to prevent a particular entry from aging out. The software
removes a dynamic entry from the ARP cache if the ARP aging interval expires before the entry is
refreshed. Static entries do not age out, regardless of whether the Brocade device receives an ARP
request from the device that has the entry's address.
You can increase the number of configurable static ARP entries. Refer to
number of entries the static ARP table can hold"
To display the ARP cache and static ARP table, see the following:
•
•
To create a static ARP entry for a static MAC entry, enter a command such as the following.
BigIron RX(config)# arp 1 192.53.4.2 1245.7654.2348 e 1/2
The command adds a static ARP entry that maps IP address 192.53.4.2 to MAC address
1245.7654.2348. The entry is for a MAC address connected to port 1/2 of the device.
Syntax: arp <ip-addr> <mac-addr> ethernet <slot/port>
The <ip-addr> command specifies the IP address of the device that has the MAC address of the
entry.
BigIron RX Series Configuration Guide
53-1001986-01
To display the ARP table, refer to
To display the static ARP table, refer to
Configuring ARP parameters
on page 190.
"Displaying the ARP cache"
"Displaying the static ARP table"
"Changing the maximum
on page 222.
on page 224.
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