TCP IP Illustrated

49 summary arp is a basic protocol in almost every

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Unformatted text preview: administrator being aware. The ARP cache is fundamental to its operation, and we've used the arp command to examine and manipulate the cache. Each entry in the cache has a timer that is used to remove both incomplete and completed entries. "The arp command displays and modifies entries in the ARP cache. We followed through the normal operation of ARP along with specialized versions: proxy ARP (when a router answers ARP requests for hosts accessible on another of the router's interfaces) and gratuitous ARP (sending an ARP request for your own IP address, normally when bootstrapping). Exercises 4.1 In the commands we typed to generate the output shown in Figure 4.4, what would happen if, after verifying that the local ARP cache was empty, we type the command bsdi % rsh svr4 arp -a to verify that the ARP cache is also empty on the destination host? (This command causes the arp -a command to be executed on the host svr4.) 4.2 Describe a test to determine if a given host handles a received gratuitous ARP request correctly file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/arp_addr.htm (11 of 12) [12/09/2001 14.46.39] Chapter 4. ARP: Address Resolution Protocol 4.3 Step 7 in Section 4.2 can take a while (milliseconds) because a packet is sent and ARP then waits for the response. How do you think ARP handles multiple datagrams that arrive from IP for the same destination address during this period? 4.4 At the end of Section 4.5 we mentioned that the Host Requirements RFC and Berkeley-derived implementations differ in their handling of the timeout of an active ARP entry. What happens if we're on a Berkeley-derived client and keep trying to contact a server host that's been taken down to replace its Ethernet board? Does this change if the server issues a gratuitous ARP when it bootstraps? file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/arp_addr.htm (12 of 12) [12/09/2001 14.46.39] Chapter 5. RARP: Reverse Address Resolution Protocol RARP: Re...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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