Example 3b: Cisco Catalyst 3750 (12.2(25)SE) snooping IGMP v2 with one receiver

This is a repeat of example 1, just forcing IGMP v2 instead of v3. Everything works as expected. The switch spoofs the group-specific leave query before telling the router to prune the group. This leads to longer leave latency as the switch waits 5 seconds while the router's leave latency is 2 seconds. Unexpectedly, group-specific membership queries are flooded to all ports, perhaps because by the time these are sent, the switch has removed multicast state for this group.

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.

The traces

Raw tcpdump traces are here:

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