Please Whitelist This Site?
I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)
If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.
If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.
Thanks for your understanding!
Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide
NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.
Reverse Address Resolution and the TCP/IP Reverse Address Resolution Protocol (RARP)
(Page 2 of 4)
The Reverse Address Resolution Protocol (RARP)
The first method devised to address
the bootstrapping problem in TCP/IP was the backwards use of ARP I mentioned
above. This technique was formalized in RFC 903, A Reverse Address
Resolution Protocol (RARP), published in 1984. Where ARP allows
device A to say I am device A and I have device
B's IP address, device B please tell me your hardware
address, RARP is used by device A to say I am device
A and I am sending this broadcast using my hardware address,
can someone please tell me my IP address?.The two-step
operation of RARP is illustrated in Figure 52.
Figure 52: Operation of the Reverse Address Resolution Protocol (RARP)
RARP, as the name suggests, works like ARP but in reverse, so this diagram is similar to Figure 47. Here, instead of Device A providing the IP address of another device and asking for its hardware address, it is providing its own hardware address and asking for an IP address it can use. The answer, in this case, is provided by Device D, which is serving as an RARP server for this network.
The next question then
is: who knows A's IP address if device A doesn't? The
answer is that a special RARP server must be configured to listen
for RARP requests and issue replies to them. Each physical network where
RARP is in use must have RARP software running on at least one machine.
RARP is not only very similar to
ARP, it basically is ARP. What I mean by this is that
RFC 903 doesn't define a whole new protocol from scratch, it just describes
a new method for using ARP to perform the opposite of its normal function.
RARP uses ARP messages in exactly
the same format as ARP, but uses different
opcodes to accomplish its reverse function. Just as in ARP, a request
and reply are used in an exchange. The
meaning of the address fields is the same
too: the sender is the device transmitting a message while the target
is the one receiving it.
Key Concept: The Reverse Address Resolution Protocol (RARP) is the earliest and simplest protocol designed to allow a device to obtain an IP address for use on a TCP/IP network. It is based directly on ARP and works in basically the same way, but in reverse: a device sends a request containing its hardware address and a device set up as an RARP server responds back with the devices assigned IP address.
|If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!|
Table Of Contents - Contact Us
The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.