UMN:CLI
User Manual
V8102
278
The host A needs the MAC address of the host D to reach the host D. Therefore, the host
A broadcasts an ARP request on the subnet A, including the V8102
’s br1 interface, but
does not reach the host D. By default, the V8102 does not forward broadcasts. Since the
V8102 knows that the target address (the host D
’s IP address) is on another subnet and
can reach the host D, it will reply with its own MAC address to the host A.
The proxy ARP replies that the V8102 sends to the host A. The proxy ARP reply packet is
encapsulated in an Ethernet frame with its MAC address as the source address and the
host A
’s MAC address as the destination address. The ARP replies are always unicast to
the original requester. On receiving this ARP reply, the host A updates its ARP table.
From now on, the host A will forward all the packets that it wants to reach the host D to
the MAC address of the V8102. Since the V8102 knows how to reach the host D, the
router forwards the packet to the host D. The ARP cache on the hosts in the subnet A is
populated with the MAC address of the V8102 for all the hosts on the subnet B. Hence,
all packets destined to the subnet B are sent to the router. The V8102 forwards those
packets to the hosts in the subnet B.
To configure the interface to accept and respond to proxy ARP, use the following com-
mand on
Interface Configuration
mode.
Command
Mode
Description
ip proxy-arp
Interface
[VLAN]
Enables the proxy ARP function on specific interface.
no ip proxy-arp
Disables the proxy ARP function.
