TCP IP Illustrated

000 1402521332 gateway 1402521335 127001 140252129

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Unformatted text preview: all datagrams for 224.0.0.0 are sent to the Ethernet: sun % netstat -rn Routing tables file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/igmp_int.htm (4 of 7) [12/09/2001 14.47.02] Chapter 13. IGMP: Internet Group Management Protocol Destination 140.252.13.65 127.0.0.1 140.252.1.183 default 224.0.0.0 140.252.13.32 Gateway 140.252.13.35 127.0.0.1 140.252.1.29 140.252.1.183 140.252.13.33 140.252.13.33 Flags UGH UH UH UG U U Refcnt 0 1 0 0 0 8 Use 32 381 6 328 66 5581 Interface le0 lo0 sl0 sl0 le0 le0 If you compare this routing table to the one shown in Section 9.2 for the router sun, you'll see that the multicast entry is the only change. We now run a test program that lets us join a multicast group on an interface. (We don't show any output for our use of this test program.) We join the group 224.1.2.3 on the Ethernet interface (140.252.13.33). Executing netstat shows that the kernel has joined the group, and again the Ethernet address is what we expect. We show the changes from the previous netstat output in a bold font: sun % netstat -nia Address Name Mtu Network lpkts le0 1500 140.252.13. 140.252.13.33 4374 224.1.2.3 224.0.0.1 08:00:20:03:f6:42 01:00:5e:01:02:03 01:00:5e:00:00:01 140.252.1.29 sl0 552 140.252.1 13862 224.0.0.1 127.0.0.1 lo0 1536 127 1360 224.0.0.1 lerrs Opkts Oerrs Coll 0 0 4929 0 0 15943 0 0 0 1360 0 0 We have shown the output again for the other two interfaces, sl0 and lo0, to reiterate that the multicast group is joined only on one interface. Figure 13.4 shows the tcpdump output corresponding to the process joining the multicast group. 1 0.0 2 6.94 (6.94) 8:0:20:3:f6:42 1:0:5e:1:2:3 ip 60: sun > 224.1.2.3: igmp report 224.1.2.3 [ttl 1] 8:0:20:3:f6:42 1:0:5e:1:2:3 ip 60: sun > 224.1.2.3: igmp report 224.1.2.3 [ttl 1] Figure 13.4 tcpdump output when a host joins a multicast group. Line 1 occurs when the host joins the group. The next line is the delayed report that we said is sent at some random time up to 10 seconds afterwar...
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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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