We know in browser inside input network address that are us, DNS server meeting automatic its analysis is IP address, what browser is sought actually is that IP address instead of network address. So, IP address how to change , is second layer physical address( MAC address)? In local area network, this is completed through ARP agreement. ARP agreement has important meaning safely for network. Through forging IP address and MAC address, realize ARP deception, producing plenty of ARP communication quantity in network make network block. So, network managements should understand ARP agreement further.
One and what
ARP agreement is " Address Resolution Protocol"( address analysis agreement) abbreviation. In local area network, in network, what reality transmit is " ", inside , it has the MAC address of goal host computer. In ethernet, a host computer is wanted , carry out direct communication with another host computer, must want to know the MAC address of goal host computer. But this goal MAC address is how to get? It is gotten through address analysis agreement. Claiming " address analysis" is host computer becomes goal IP address conversion before sending the process of goal MAC address. The basic skill of ARP agreement can be the MAC address of the IP address and inquiry goal equipment that passes through goal equipment , with guarantee communication go on smoothly.
The working principle
When each installation TCP / IP has a ARP in the computer
Subordinate
Ip address
192.168.1.100-aa-00-62-c6-09
192.168.1.200-aa-00-62-c5-03
192.168.1.303-aa-01-75-c3-06
. . . .
We send data with A of host computer( 192.168.1.5) to B of host computer( 192.168.1.1), is regular. When send data, in ARP of host computer of A meeting in self stores table slowly seek whether have goal IP address. If have found , have also known goal MAC address , directly write in goal MAC address inside sends may; Have not found if in ARP, storing table slowly relative should IP address, it is " FF.FF.FF.FF.FF.FF" that A of host computer will send a broadcasting, goal MAC address on network, this expression to same net part have host computer to send such inquiry: " 192.168, what is the MAC address of 1.1? " the other host computers on network do not respond ARP to inquire , only when B of host computer takes over this , just makes such response to A of host computer: " 192.168, the MAC address of 1.1 is 00-aa-00-62-c6-09 ". Is so, A of host computer has known MAC of B of host computer address, it may send message to B of host computer. At the same time, it has still updated own ARP to store table slowly , send message next time again to B of host computer in, directly store table slowly from ARP search may. ARP stores table slowly, have adopted ageing mechanism, in a time if the certain in table no use, will be deleted , may so reduce ARP greatly to store the length of table slowly , quickly inquire speed.
3, how to look
It may look over that ARP stores table slowly, may also add
May delete the content of the certain in ARP table with the order
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