Multicast at 1000 Mbits/s works, but 100 Mbts/s don't.

[Paris]

Hello community, I have a
problem while I'm uploading an image with my fog server: multicast works well with my X440 switches (1000 Mbits/s) but with my x250 (100 Mbits/s) it stops after ~5min. It resumes when I restart all my ports concerned by my deployment: (my fog server and PCs).

When it stops, my PC unsubscribe to the udpcast group and resuscribe when I restart my ports.

I have the same issue when i configure my X440 PC ports at 100Mbits/s.

There is nothing in my logs that says that's my ports are blocked or somethings...

What do you suggest me to check ?


Thanks!

Best regards,
Adrien, from France.

[Paris]

Thanks for your help, it is actually a problem of IGMP snooping, i will fix this problem.

Best regards,
Adrien, from France.

[Erik_Auerswald]

Hi,

the problem description hints at a missing IGMP querier.

On EXOS, the querier is configured on a VLAN that has an IP address using the following command:
enable igmp vlan VLAN_NAME IGMP_VERSION This enables IGMP queries in this VLAN, allowing IP multicast to work correctly inside this VLAN.

IGMP snooping, enabled by default, requires either bidirectional multicast traffic or regular IGMP messages to keep the cache entries current. The relevant messages are created when an end system joins the group, thus multicast initially works, but this time out if there is no querier in the VLAN to trigger recurring group membership messages from the end systems.

To transport multicast from one VLAN to another needs additional mechanisms, e.g. multicast routing using PIM.

Thanks,
Erik

[Kawawa]

Out of curiosity, does the VLAN where the receiver is have an IP? IGMP snooping requires at least one querier to be present in the VLAN and the querier should have an IP. The querier will poll subscribed hosts to see if they are still interested in a stream. And if the querier doesn't receive any responses it ages the host. The default host timeout is 260 seconds (around 4 minutes). Here's an example:

# show igmp snooping v70Router Timeout : 260 secHost Timeout : 260 secIgmp Snooping Fast Leave Time : 1000 msVLAN v70 (70) Snooping=Enabled Group Sender Age 239.0.0.10 70.0.0.2 15 1 Incoming multicast streams Port Host Subscribed Age Group-Limit 21 70.0.0.3 239.255.255.250 253 0 Once the 260 seconds elapses, the host is disconnected from the stream:
# show igmp snooping v70Router Timeout : 260 sec
Host Timeout : 260 sec
Igmp Snooping Fast Leave Time : 1000 ms
VLAN v70 (70) Snooping=Enabled
Group Sender Age
239.0.0.10 70.0.0.2 5
1 Incoming multicast streams Then I disable and re-enable the host port and the stream is back:
# disable ports 20# enable ports 20
# show igmp snooping v70
Router Timeout : 260 sec
Host Timeout : 260 sec
Igmp Snooping Fast Leave Time : 1000 ms
VLAN v70 (70) Snooping=Enabled
Group Sender Age
239.0.0.10 70.0.0.2 5
1 Incoming multicast streams

[OscarK]

The client should subscribe to the streams and keep that subsciption alive by sending a report when a switch is asking (query) for it. The switch should do a query before removing a port from the stream, you could do a capture to see if you get that igmp query and if the client responds to it.