TCP IP Illustrated

004 224123 224004 224999 figure 135 tcpdump output

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Unformatted text preview: 4.0.0.4: 224.9.9.9: 224.0.0.1: 224.9.9.9: 224.1.2.3: 224.0.0.4: 224.0.0.1: 224.1.2.3: 224.0.0.4: 224.9.9.9: igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp igmp report query report query report report report query report report report query report report report 224.0.0.4 224.9.9.9 224.1.2.3 224.0.0.4 224.9.9.9 224.9.9.9 224.1.2.3 224.0.0.4 224.1.2.3 224.0.0.4 224.9.9.9 Figure 13.5 tcpdump output while multicast routing daemon is running. We have not included the Ethernet addresses in this output, because we've already verified that they are what we expect. We've also deleted the notation that the TTL equals 1, because again that's what we expect. Line 1 is output when the routing daemon starts. It sends a report that it has joined the group 224.0.0.4. Multicast address 224.0.0.4 is a well-known address used by DVMRP (Distance Vector Multicast Routing Protocol), the protocol currently used for multicast routing. (DVMRP is defined in RFC 1075 [Waitzman, Partridge, and Deering 1988].) When the daemon starts it also sends out a query (line 2). The destination IP address of the query is 224.0.0.1 file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/igmp_int.htm (6 of 7) [12/09/2001 14.47.02] Chapter 13. IGMP: Internet Group Management Protocol (all-hosts), as shown in Figure 13.3. The first report (line 3) is received about 5 seconds later, for group 224.9.9.9. This is the only report received before another query is sent (line 4). These two queries (lines 2 and 4) occur rapidly when the daemon starts up, as it tries to build its multicast routing table. Lines 5, 6, and 7 are what we expect: one report from the host sun for each group to which it belongs. Notice that the group 224.0.0.4 is reported, in addition to the two groups that we explicitly joined, because as long as the routing daemon is running, it belongs to this group. The next query on line 8 occurs about 2 minutes after the previous query. Again it elicits the three reports we expect (lines 9, 10, a...
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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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