Allied Telesis AT-S63 - Manual (Page 558)

Chapter 32: Internet Protocol Version 4 Packet Routing
558 Section VII: Internet Protocol Routing
The maximum storage capacity of the routing table in the AT-9400 Series
switch is:
ˆ 512 interface routes
ˆ 1024 static routes
ˆ 1024 RIP routes
Address
Resolution
Protocol (ARP)
Table
The switch maintains an ARP table of IP addresses and the matching
Ethernet MAC addresses. It refers to the table when routing packets to
determine the destination MAC addresses of the nodes, as well as
interfaces and ports from where the nodes are reached.
The ARP table can store both static and dynamic entries. Static entries are
entries you add yourself. This type of entry is never removed by the switch
from the ARP table, even when the corresponding nodes are inactive.
Dynamic entries are entries that the switch learns on it own. Dynamic
entries of inactive nodes are periodically removed from table to prevent
the table from filling with entries of inactive nodes.
The switch learns addresses by sending out ARP requests. It generates
an ARP request whenever it receives a packet that needs to be routed
across a subnet, but lacks the destination MAC address in its ARP table.
The switch, after receiving the ARP response from the destination node,
adds the IP address and MAC address of the node to its ARP table and
begins to route packets to the device. It should be noted that the switch
discards all packets intended to a destination node until it receives a
respond to its ARP request.
The switch can also learn addresses when it is the destination of an ARP
request from another node, such as when it is pinged by a management
station. The switch adds the source IP address and MAC address in the
request from the node to the table when it responds to the ARP request.
Dynamic ARP entries are aged from the table according to the ARP cache
timeout value to protect the table from filling with entries for hosts which
are no longer active. Old entries are deleted. The default setting for the
timeout value is 150 seconds. This value is adjustable with the SET IP
ARP TIMEOUT command. Static ARP entries are not aged and are
retained in the table even when the nodes are inactive.
The commands for managing the ARP table are “ADD IP ARP” on
page 571, “DELETE IP ARP” on page 580, “SET IP ARP” on page 588,
“SET IP ARP TIMEOUT” on page 589, and “SHOW IP ARP” on page 597.
Note
The switch does not support Proxy ARP.