Welcome to TCP/IP Part 6

To further our use and understanding of our introduction of TCP/IP, we will continue on with some necessary protocols.  More importantly, Address Resolution Protocols.

Address Resolution Protocol (ARP) is the protocol which is used to find the address host from a known IP address.  ARP sends out a broadcast to the network asking for the machine with the specific IP address.  In essence, ARP translates the IP address into a hardware address.

ARP

Reverse Address Resolution Protocol (RARP) is the protocol used to discover the identity of the IP address for diskless machines and essentially requests for the IP address of itself through other equipment by sending out its MAC address.  Recall that DHCP is the protocol used to determine who is assigned what IP address (Welcome to TCP/IP Part 2).  On a side note, most home networks set their routers up to assign the IP addresses to their equipment throughout their home.

RARP

Proxy Address Resolution Protocol (PARP) is the protocol used to help machines on a subnet reach remote subnets without configuring routing or a default gateway.  The detriment to using Proxy ARP is that it will severely increase the traffic on your network.  And you thought a slow network was bad?  Most medium to large businesses can handle the traffic, home networks not so easily.  It is configured on all Cisco routers by default.

PrARP

This is what would be shown in the ARP cache memory of Host A.

IP Address

MAC Address

172.16.20.200 00-00-0c-94-36-ab
172.16.20.100 00-00-0c-94-36-ab
172.16.10.99 00-00-0c-94-36-ab
172.16.10.200 00-00-0c-94-36-bb

Next week, we will discuss IP Addressing, until then…

See also:  Part 1, Part 2, Part 3, Part 4, Part 5

Works Cited

Cisco Systems, Inc. (2008, January 28). Document ID: 13718. Retrieved January 08, 2013, from Cisco: http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094adb.shtml

Lammle, T. (2007). CCNA Cisco Certified Network Associate Study Guide. Indianapolis: Wiley Publishing, Inc.

Odom, W. (2012). Official Cert Guide ICND1 640-822. Indianapolis, IN: Cisco Press.

Odom, W. (2011). Official Cert Guide ICND2 640-816. Indianapolis, IN: Cisco Press.

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