Address Resolution Protocol(ARP) - Address Resolution Protocol (ARP) is a low-level network protocol use IP address to find MAC address.
· The Address Resolution Protocol (ARP) was developed to enable communications on a network.
· Each and every device who is work on IP need ARP to map IP addresses to MAC addresses so that IP packets can be sent across networks.
· ARP packet always broadcast on the network.
· ARP table use to creates a data-link header and trailer that encapsulates the packet,
· ARP cache use to storing MAC in memory for a period of time as the addresses are learned.
· There are two types of ARP cache entry
· 1)static ARP cache entries
· 2)dynamic ARP cache entries.
· Static entries are manually configured entry and kept in the cache table on permanent basis.
· Dynamic entries are added by Cisco software and its kept for a period of time and then removed.
· The ARP table is built and changed automatically
· The default time limit is 4 hours.
Take a look of ARP Cache Content: -
Protocol: - its define the TCP/IP Internet Layer.
Address: - Its define the Logical IP address that binding on define hardware address.
Age: - Its define MAC storage time in minutes
Hardware Address: - Its define the MAC address binding on Logical ip address.
Type: - In type field ARPA define the Ethernet frame which is currently used by the Internet Protocol.
Configure Static ARP Entry: -
Types of ARP: -
1) ARP : - It's mapping of Layer 3 address to a Layer 2 address.
2) Reverse ARP : - it is mapping of Layer 2 address to a Layer 3 address.
3) Proxy ARP : - Proxy ARP use to respond the ARP requests with wrong MAC Address for a destination which is not in same network.
4) Gratuitous ARP: - Gratuitous ARP use for Duplicate address detection.