ARP command brief

ARP is an important TCP/IP protocol and is used to determine the physical address of the NIC corresponding to the IP address. Use the arp command to view the current contents of the ARP cache on the local or another computer. Further, by arp command, enter the static physical network card /IP address of a manually.

according to the default settings, the ARP cache item is dynamic, every time the transmission ARP automatically adds the data item at a specified location and the current item does not exist in the cache. Once the cached items are entered, they have begun to go to a failed state. For example, in a Windows NT/2000 network, if you do not use it further after entering the project, the physical/IP address pair will expire in 2 to 10 minutes. Therefore, if there are few or no items in the ARP cache, they can be added by a ping command from another computer or router. Therefore, when you need to view the contents of the cache through the arp command, you can ping this computer first (you cannot send the ping command locally).

ARP Common command options:


arp -a or arp -g

for viewing cache All items in . The results of the -a and -g parameters are the same. Over the years -g has been the option to display all the items in the ARP cache on UNIX platforms, while Windows uses arp -a (-a can be treated as all, That is all the meaning), but it can also accept the more traditional -g option.

arp -a IP

If we have more than one card, then use arp -a plus IP address of the interface, you can only Displays the ARP cache entries associated with this interface.


arp -s IP physical address

we can manually enter a static entry to the ARP cache. The project will remain active during the computer boot process, or the manually configured physical address will automatically update the project in the event of an error.


arp -d IP

can use this command to manually delete a static item.

Example:
interfaces to show all the ARP cache table, type:
arp -a
for the assigned IP address 10.0.0.99 interface, to show its ARP cache table, type:

arp -a -N 10.0.0.99
to add IP address 10.0.0.80 resolved to a physical address 00-AA-00 -4F-2A-9C Static ARP Cache entry, type:
arp -s 10.0.0.80 00-AA-00-4F-2A-9C