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Lectures notes for 2010 - KTH

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RARP: Reverse Address Resolution Protocol<br />

(RFC 903)<br />

How do you get you own IP address, when all you know is your link address?<br />

• Necessary if you don’t have a disk or other stable store<br />

• RARP request - broadcast to every host on the network<br />

(i.e., EtherDST=0xFFFFFFFFFFFF), TYPE=0x8035<br />

• RARP server: “I know that address!” and sends an RARP reply<br />

• Source host - receives the RARP reply, and now knows its own IP addr<br />

EtherDST EtherSRC<br />

6 6<br />

TYPE<br />

2<br />

OP=Request½≡3, Reply≡4<br />

hardware<br />

type<br />

protocol<br />

type<br />

hardware<br />

length<br />

protocol<br />

length<br />

OP<br />

sender<br />

ether addr<br />

sender<br />

IP<br />

2 2 1 1 2 6 4 6<br />

Figure 8: Format of RARP request/reply packet<br />

target<br />

ether addr target<br />

IP<br />

Note: You can now see what the “publish” aspect of the arp command is <strong>for</strong>.<br />

4<br />

Maguire RARP: Reverse Address Resolution Protocol (RFC 903) 2: 30 of 52<br />

maguire@kth.se <strong>2010</strong>.03.21 Internetworking/Internetteknik

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