Web Management Guide-R04

Table Of Contents
Chapter 15
| Basic IP Functions
Address Resolution Protocol
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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.
Also, if the switch receives a request for its own IP address, it will send back a
response, and also cache the MAC of the source device's IP address.
Basic ARP
Configuration
Use the Tools > ARP (Configure General) page to specify the timeout for ARP cache
entries, or to enable Proxy ARP for specific VLAN interfaces.
Command Usage
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 request by sending its own MAC address to the
requesting node. That node then sends traffic to the router, which in turn uses its
own routing table to forward the traffic to the remote destination.
Figure 440: Proxy ARP
Parameters
These parameters are displayed:
Timeout – Sets the aging time for dynamic entries in the ARP cache.
(Range: 300 - 86400 seconds; Default: 1200 seconds or 20 minutes)
The ARP aging timeout can be set for any configured VLAN.
The aging time determines how long dynamic entries remain in the cache. If
the timeout is too short, the router may tie up resources by repeating ARP
requests for addresses recently flushed from the table.
When a ARP entry expires, it is deleted from the cache and an ARP request
packet is sent to re-establish the MAC address.
no routing,
no default
gateway
Remote
ARP Server
Proxy ARP
ARP
request