User Manual

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Users Manual of XGS-6350-24X4C
ARP is used to map IP addresses to media or MAC address. When the IP address is known, ARP will find the
corresponding MAC address. When the MAC address is known, the mapping relationship between IP address
and MAC address is saved in ARP cache for rapid access. The IP message is then packaged in the message
at the link layer and at last is sent to the network.
 Defining a static ARP cache
ARP and other address resolution protocols provide a dynamic mapping between IP address and MAC
address. The static ARP cache item is generally not required because most hosts support dynamic address
resolution. You can define it in global configuration mode if necessary. The system utilizes the static ARP
cache item to translate the 32-bit IP address into a 48-bit MAC address. Additionally, you can specify the
routing switch to respond to the ARP request for other hosts.
You can set the active period for the ARP items if you do not want the ARP item to exist permanently. The
following two types show how to configure the mapping between the static IP address and the MAC address.
Run one of the following commands in global configuration mode:
Run… To…
arp ip-address hardware-address
Globally map an IP address to a MAC
address in the ARP cache.
arp ip-address hardware-address
alias
Specify the routing switch to respond
to the ARP request of the designated
IP address through the MAC address
of the routing switch.
Run the following command in interface configuration mode:
Run… To…
arp timeoutseconds
Set the timeout time of the ARP cache
item in the ARP cache.
Run show interfaces to display the ARP timeout time of the designated interface. Run the show arp to check
the content of the ARP cache. Run clear arp-cache to delete all items in the ARP cache.
 Activating proxy ARP
The system uses the proxy ARP (defined by RFC 1027) to obtain the host’s MAC address on other networks
for the hosts without corresponding routes. For example, when the routing switch receives an ARP request
and finds that the source host and the destination host are not connected to the same interface and all the
routes that the routing switch reaches the destination host are not through the interface that receives the ARP
request, it will send a proxy ARP response that contains its address of the link layer. The source host then
sends the message to the routing switch and the switch forwards it to the destination host. The proxy ARP is
activates by default.