User's Manual

Table Of Contents
392
Users Manual of CS-6306R
the link layer from the IP address is called as Address Resolution Protocol (ARP). The process on how to
obtain the IP address from the local address of the link layer is called as Reverse Address Resolution
(RARP).
Our system adopts address resolution in two types: ARP and proxy ARP. The ARP and proxy ARP are
defined in RFC 860 and 1027 respectively.
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.