Checking multicast groups

Use this procedure to check multicast groups for proper membership.

To check multicast groups for proper membership, perform the following procedure:

If you are running a host-based subnet manager, to check multicast group creation, on the fabric management server run a query for the specific subnet. Remember that you must provide the HCA and port through which the subnet manager connects to the subnet.
```
/sbin/saquery –o mcmember –h [HCA] –p [HCA port]
```
Each interface produces an entry like the following example. Note the 4 KB maximum transmission unit (MTU) and 20 g rate.
```
GID: 0xff12601bffff0000:0x0000000000000016
PortGid: 0xfe80000000000000:0002550070010f00
MLID: 0xc004 PKey: 0xffff Mtu: 4096 Rate:  20g PktLifeTime: 2147 ms
QKey: 0x00000000 SL:  0 FlowLabel: 0x00000  HopLimit: 0xff  TClass:  0x00
```
Note: You can check for misconfigured interfaces by using something like the following example, which looks for any MTU that is not 4096 or rate is 10 g:
```
/sbin/saquery –o mcmember –h [HCA] –p [port] | egrep –B 3 –A 1 ‘Mtu: [0-
3]|Rate:  10g'
```
If you are running an embedded subnet manager, to check multicast group creation, run the following command on each switch with a master subnet manager. If you have set it up, you might use the dsh command from the Cluster Systems Management/Management Server (CSM/MS) to the switches. For details, see Setting up remote command processing. Remember to use --devicetype IBSwitch::Qlogic when pointing to the switches.
```
smShowGroups
```
There should be just one group with all the HCA devices on the subnet being part of the group.
Note: MTU=5 indicates 4 KB. MTU=4 indicates 2 KB.

The following example shows 4 KB MTU.
```
0xff12401bffff0000:00000000ffffffff (c000)
  qKey = 0x00000000  pKey = 0xFFFF  mtu = 5  rate = 3  life = 19  sl = 0
  0x00025500101a3300 F  0x00025500101a3100 F  0x00025500101a8300 F
  0x00025500101a8100 F  0x00025500101a6300 F  0x00025500101a6100 F
  0x0002550010194000 F  0x0002550010193e00 F  0x00066a00facade01 F
```