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GS108Tv2 flooding multicast at regular intervals
Hi All,
Just bought a 2nd hand GS108Tv2. Configured management IP & upgraded to latest firmware. Then configured IGMP Snooping global plus VLAN's 1 & 3. All ports are members of both 1 & 3 untagged.
- On Port-3 I have a Video Streamer sending multicast to the switch.
- On Port-6 I have Macbook with VCL, etc.
With no client running on the Mac, I can periodically see the Multicast arriving using "tcpdump". The switch seems to be flooding multicast for about 20-30 seconds, and then dropping as it should, but only for 20-30 seconds. This cycle repeats regularly. See attached screenshot !!
Is this typical behaviour ? I thought the GS108T was able to manage multicast ?
Thanks,
Pete
I think I resolved the issue. GS108T requires IGMP configured as above, PLUS the "Block Unknown Multicast" to be enabled. Now the IGMP seems to work properly for Video.
Not sure yet if anything else using multicast is impacted.
Hope this helps others.
5 Replies
Adding to my earlier post. Attached is switch config in case any guru spots the problem.
File is PDF format becasue I cannot upload the txt version.
I think I resolved the issue. GS108T requires IGMP configured as above, PLUS the "Block Unknown Multicast" to be enabled. Now the IGMP seems to work properly for Video.
Not sure yet if anything else using multicast is impacted.
Hope this helps others.
pwood999 wrote:... VLAN's 1 & 3. All ports are members of both 1 & 3 untagged.
Pete,
What is the idea of this set-up? In a 802.1Q environment only one VLAN can be untagged on a single port or LAG, and incoming frames can be sent into one defined VLAN as configured by the PVID setting on the port.
-KurtYes I would normally expect single untagged VLAN plus a number of tagged VLAN's.
The Documentation was very unclear about the "auto-video" feature, which is basically useless in an untagged system. I tried with VLAN-1 only, but it still didnt work. My expectation was that setting IGMP snooping & querier on vlan-1 should block the packets, but I still got the 20-30 second floods.
Enabling the "block unknown multicast" stopped the floods, and now the queries work as expected.
- The usability for the auto-VLAN is useful when you want to put the registered IGMP Multicast traffic info a dedicated VLAN for handling this traffic over a higher QoS level. For consumer environments where the in-house Internet traffic and the IPTV does run on the same subnet this won't help much - because the media receiver does get it's LAN interface on the basic LAN - so making a protocol based traffic differentiation does not make a lot of sense.
Not sure what kind of traffic you have spotted there. Matter of fact, there is - depending on your computing or multimedia environment - a lot of other non-registered Multicast traffic. When you enable the block unknown Multicast traffic, several other applications can be affected.
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