Proxy Arp - SMC Networks SMC6724L3 Management Manual

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ONFIGURING THE
appropriate field in the frame header, and forwards the frame on to the
next hop. IP traffic passes along the path to its final destination in this way,
with each routing device mapping the destination IP address to the MAC
address of the next hop toward the recipient, until the packet is delivered
to the final destination.
If there is no entry for an IP address in the ARP cache, the router will
broadcast an ARP request packet to all devices on the network. The ARP
request contains the following fields similar to that shown in this example:
When devices receive this request, they discard it if their address does not
match the destination IP address in the message. However, if it does
match, they write their own hardware address into the destination MAC
address field and send the message back to the source hardware address.
When the source device receives a reply, it writes the destination IP
address and corresponding MAC address into its cache, and forwards the
IP traffic on to the next hop. As long as this entry has not timed out, the
router will be able forward traffic directly to the next hop for this
destination without having to broadcast another ARP request.

Proxy ARP

When a node in the attached subnetwork does not have routing or a
default gateway configured, Proxy ARP can be used to forward ARP
requests to a remote subnetwork. When the router receives an ARP
request for a remote network and Proxy ARP is enabled, it determines if it
has the best route to the remote network, and then answers the ARP
3-158
S
WITCH
destination IP address
destination MAC
address
source IP address
source MAC address
10.1.0.19
?
10.1.0.253
00-00-ab-cd-00-00