D-Link DES-3052 Product Manual - Page 300
ARP Packet Content ACL
UPC - 790069305351
View all D-Link DES-3052 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 300 highlights
Appendix E ARP Packet Content ACL Address Resolution Protocol (ARP) is the standard method for finding a host's hardware address (MAC address) when only its IP address is known. This protocol is vulnerable so hackers can spoof the IP and MAC information in the ARP packets to attack a LAN (known as ARP spoofing). This document is intended to introduce ARP protocol, ARP spoofing attacks, and the countermeasure devised by D-Link to put an end to ARP spoofing attacks. How Address Resolution Protocol works In the process of ARP, PC A will, firstly, issue an ARP request to query PC B's MAC address. The network structure is shown in Figure-1. Figure - 1 In the mean time, PC A's MAC address will be written into the "Sender H/W Address" and its IP address will be written into the "Sender Protocol Address" in ARP payload. As PC B's MAC address is unknown, the "Target H/W Address" will be "00-00-0000-00-00" while PC B's IP address will be written into the "Target Protocol Address", shown in Table-1. H/W Protocol H/W Protocol Operation type type address address length length Sender H/W address ARP request 00-20-5C-01-11-11 Table - 1 (ARP Payload) Sender protocol address 10.10.10.1 Target H/W address 00-00-00-00-00-00 Target protocol address 10.10.10.2 The ARP request will be encapsulated into the Ethernet frame and sent out. As can be seen in Table-2, the "Source Address" in the Ethernet frame will be PC A's MAC address. Since the ARP request is sent via a broadcast method, the "Destination address" is in the format of Ethernet broadcast (FF-FF-FF-FF-FF-FF). Destination address FF-FF-FF-FF-FF-FF Source address 00-20-5C-01-11-11 Ether-type ARP FCS Table - 2 (Ethernet frame format)