TCP IP Illustrated

Htm 9 of 17 12092001 144653 chapter 10 dynamic routing

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Unformatted text preview: ments%20and%20Settings/bigini/Docu.../homenet2run/tcpip/tcp-ip-illustrated/dynamic.htm (9 of 17) [12/09/2001 14.46.53] Chapter 10. Dynamic Routing Protocols 17.02187 gateway.tuc.noao.edu -> 140.252.1.255 RIP R (15 destinations) 20.68009 R10.tuc.noao.edu -> BROADCAST RIP R (4 destinations) 29.87848 R6.tuc.noao.edu -> 140.252.1.255 RIP R (1 destinations) 34.50209 R4.tuc.noao.edu -> 140.252.1.255 RIP R (1 destinations) 36.32385 R2.tuc.noao.edu -> 140.252.1.255 RIP R (1 destinations) 41.34565 R7.tuc.noao.edu ~> 140.252.1.255 RIP R (1 destinations) 46.19257 R8.tuc.noao.edu -> 140.252.1.255 RIP R (1 destinations) 46.52199 R3.tuc.noao.edu -> 140.252.1.255 RIP R (1 destinations) 47.01870 gateway.tuc.noao.edu -> 140.252.1.255 RIP R (15 destinations) 50.66453 R10.tuc.noao.edu -> BROADCAST RIP R (4 destinations) Figure 10.8 RIP broadcasts captured at solaris over a 60-second period. The -P flag captures packets in nonpromiscuous mode, -tr prints the relative time-stamps, and udp port 520 captures only UDP datagrams with a source or destination port of 520. The first six packets, from R6, R4, R2, R7, R8, and R3, each advertise just one network. If we looked at the packets we would see that R6 advertises a route to 140.252.6.0 with a hop count of 1, R4 advertises a route to 140.252.4.0 with a hop count of 1, and so on. The router gateway, however, advertises 15 routes. We can run snoop with the -v flag and see the entire contents of the RIP message. (This flag outputs the entire contents of the entire packet: the Ethernet header, the IP header, the UDP header, and the RIP message. We've deleted everything except the RIP information.) Figure 10.9 shows the output. Compare these advertised hop counts on the 140.252.1 network with the topology shown in Figure 10.7. A puzzle in the output in Figure 10.8 is why R10 is advertising four networks when Figure 10.7 shows only three. If we look at the RIP packet with snoop we see the following advertised routes: file:///D|/Documen...
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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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