Note: the Catalyst switch also has an immediate leave option which was not enabled. Immediate leave assumes that there are no downstream hubs or switches such that there may be multiple hosts with group interest on the same switch port.
host 10
host 11
host 12
host 13
switch console log
router console log
Host 10 joins group. Two membership reports are sent up to switch but one appears to be suppressed. One is passed through unmodified to router, but is supressed out other switch ports (so hosts 11 and 12 don't hear it). | |
host 10 | No. Time Source Destination Protocol Info 5 186.496725 128.59.7.10 224.5.6.7 IGMP V2 Membership Report Frame 5 (46 bytes on wire, 46 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Report (0x16) Max Response Time: 0.0 sec (0x00) Header checksum: 0x03f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 6 186.539700 128.59.7.10 224.5.6.7 IGMP V2 Membership Report Frame 6 (46 bytes on wire, 46 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Report (0x16) Max Response Time: 0.0 sec (0x00) Header checksum: 0x03f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
host 13 | No. Time Source Destination Protocol Info 5 186.499122 128.59.7.10 224.5.6.7 IGMP V2 Membership Report Frame 5 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Report (0x16) Max Response Time: 0.0 sec (0x00) Header checksum: 0x03f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
host 11 | nothing |
host 12 | nothing |
Data starts to flow. Host 13 sees it come down from router which passes through to host 10 only, as it should. | |
host 13 | No. Time Source Destination Protocol Info 6 186.641083 128.59.39.150 224.5.6.7 UDP Source port: 32970 Destination port: 8910 Frame 6 (1512 bytes on wire, 1500 bytes captured) Ethernet II, Src: 00:08:7c:d0:08:40, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.39.150 (128.59.39.150), Dst Addr: 224.5.6.7 (224.5.6.7) User Datagram Protocol, Src Port: 32970 (32970), Dst Port: 8910 (8910) Data (1458 bytes) |
host 10 | No. Time Source Destination Protocol Info 7 186.640204 128.59.39.150 224.5.6.7 UDP Source port: 32970 Destination port: 8910 Frame 7 (1512 bytes on wire, 1500 bytes captured) Ethernet II, Src: 00:08:7c:d0:08:40, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.39.150 (128.59.39.150), Dst Addr: 224.5.6.7 (224.5.6.7) User Datagram Protocol, Src Port: 32970 (32970), Dst Port: 8910 (8910) Data (1458 bytes) |
host 11 | nothing |
host 12 | nothing |
switch | Switch>show ip igmp snooping groups vlan 950 224.5.6.7 Vlan Group Type Version Port List ------------------------------------------------------------- 950 224.5.6.7 igmp v2 Fa1/0/1, Fa1/0/3 |
router | wat-edge-1#sho ip igmp groups fa7/37 IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter 224.5.6.7 FastEthernet7/37 00:00:02 00:02:57 128.59.7.10 |
Data keeps flowing and the router sends out a routine general membership query every 60 seconds which is flooded out all switch ports. Host 10 also sends periodic unsolicited membership reports, which are suppressed and are not sent up to the router; Only responses to general membership queries are sent through to the router. | |
host 13 | No. Time Source Destination Protocol Info 62 242.291847 128.59.7.1 224.0.0.1 IGMP V2 Membership Query Frame 62 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:00:00:01 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.0.0.1 (224.0.0.1) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 10.0 sec (0x64) Header checksum: 0xee9b (correct) Multicast Address: 0.0.0.0 (0.0.0.0) |
host 10 | No. Time Source Destination Protocol Info 14 192.793751 128.59.7.10 224.5.6.7 IGMP V2 Membership Report Frame 14 (46 bytes on wire, 46 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Report (0x16) Max Response Time: 0.0 sec (0x00) Header checksum: 0x03f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 64 242.290527 128.59.7.1 224.0.0.1 IGMP V2 Membership Query Frame 64 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:00:00:01 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.0.0.1 (224.0.0.1) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 10.0 sec (0x64) Header checksum: 0xee9b (correct) Multicast Address: 0.0.0.0 (0.0.0.0) No. Time Source Destination Protocol Info 68 245.296766 128.59.7.10 224.5.6.7 IGMP V2 Membership Report Frame 68 (46 bytes on wire, 46 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Report (0x16) Max Response Time: 0.0 sec (0x00) Header checksum: 0x03f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
host 11 & 12 | No. Time Source Destination Protocol Info 5 242.293638 128.59.7.1 224.0.0.1 IGMP V2 Membership Query Frame 5 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:00:00:01 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.0.0.1 (224.0.0.1) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 10.0 sec (0x64) Header checksum: 0xee9b (correct) Multicast Address: 0.0.0.0 (0.0.0.0) |
Host 10 leaves group, sends a leave, which is suppressed by the switch. The switch turns around and spoofs a group-specific query with a 5 second max timeout. Nobody replies since host 10 is the only host on the given switch port. | |
host 10 | No. Time Source Destination Protocol Info 92 267.836324 128.59.7.10 224.0.0.2 IGMP V2 Leave Group Frame 92 (46 bytes on wire, 46 bytes captured) Ethernet II, Src: 00:00:86:51:bd:b2, Dst: 01:00:5e:00:00:02 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.0.0.2 (224.0.0.2) Internet Group Management Protocol IGMP Version: 2 Type: Leave Group (0x17) Max Response Time: 0.0 sec (0x00) Header checksum: 0x02f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 93 267.836707 128.59.7.1 224.5.6.7 IGMP V2 Membership Query Frame 93 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:0f:8f:c7:27:85, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 5.0 sec (0x32) Header checksum: 0x08c1 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
host 11 | nothing |
host 12 | nothing |
host 13 | nothing |
After 5 seconds have elapsed with no reply to the spoofed group-specific query, the switch spoofs (forwards) host 10's leave up to the router -- 5 seconds after the host generated it. The router responds with two group-specific queries with a 1 second max response time. The switch forwards these to all ports which seems incorrect -- only ports with established group interest should receive the group-specific query. Unlike the HP, no data packets leak out along with the group-specific query. After the second group-specific query gets no response within the specified one-second interval, traffic to the group is pruned by the router. It had already been pruned by the switch 2 seconds earlier. | |
host 10 | No. Time Source Destination Protocol Info 98 272.640297 128.59.39.150 224.5.6.7 UDP Source port: 32970 Destination port: 8910 Frame 98 (1512 bytes on wire, 1500 bytes captured) Ethernet II, Src: 00:08:7c:d0:08:40, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.39.150 (128.59.39.150), Dst Addr: 224.5.6.7 (224.5.6.7) User Datagram Protocol, Src Port: 32970 (32970), Dst Port: 8910 (8910) Data (1458 bytes) |
host 13 | No. Time Source Destination Protocol Info 95 272.832455 128.59.7.10 224.0.0.2 IGMP V2 Leave Group Frame 95 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:0f:8f:c7:27:83, Dst: 01:00:5e:00:00:02 Internet Protocol, Src Addr: 128.59.7.10 (128.59.7.10), Dst Addr: 224.0.0.2 (224.0.0.2) Internet Group Management Protocol IGMP Version: 2 Type: Leave Group (0x17) Max Response Time: 0.0 sec (0x00) Header checksum: 0x02f3 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 96 272.837868 128.59.7.1 224.5.6.7 IGMP V2 Membership Query Frame 96 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 1.0 sec (0x0a) Header checksum: 0x08e9 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 99 274.681119 128.59.7.1 224.5.6.7 IGMP V2 Membership Query Frame 99 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 1.0 sec (0x0a) Header checksum: 0x08e9 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
host 11 & 12 | No. Time Source Destination Protocol Info 6 272.841262 128.59.7.1 224.5.6.7 IGMP V2 Membership Query Frame 6 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 1.0 sec (0x0a) Header checksum: 0x08e9 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) No. Time Source Destination Protocol Info 7 274.684613 128.59.7.1 224.5.6.7 IGMP V2 Membership Query Frame 7 (60 bytes on wire, 60 bytes captured) Ethernet II, Src: 00:d0:03:66:80:0a, Dst: 01:00:5e:05:06:07 Internet Protocol, Src Addr: 128.59.7.1 (128.59.7.1), Dst Addr: 224.5.6.7 (224.5.6.7) Internet Group Management Protocol IGMP Version: 2 Type: Membership Query (0x11) Max Response Time: 1.0 sec (0x0a) Header checksum: 0x08e9 (correct) Multicast Address: 224.5.6.7 (224.5.6.7) |
switch | Switch>show ip igmp snooping groups vlan 950 224.5.6.7 Vlan Group Type Version Port List ------------------------------------------------------------- 950 224.5.6.7 igmp v2 Fa1/0/1, Fa1/0/3 Switch>show ip igmp snooping groups vlan 950 224.5.6.7 Vlan Group Type Version Port List ------------------------------------------------------------- |
router | wat-edge-1#sho ip igmp groups fa7/37 IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter 224.5.6.7 FastEthernet7/37 00:01:27 00:00:01 128.59.7.10 wat-edge-1#sho ip igmp groups fa7/37 IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter |