Technicolor COM400 Technical Tip

Technical Tip
COM400
IGMP Query Packet Sets COM400 Port as Dynamic Router
If a COM400 receives an IGMP Query packet from a managed ethernet switch it will
automatically assign that port as a "dynamic router port" and force all multicast traffic to flow
across the connected port.
Suggested Action:
It is recommended that managed ethernet switches only be connected to the 10G ports on the
COM400 chassis, and that only management devices such as Laptops be connected to the 1G
ports. It is recommended that the Meraki router be connected to the managed ethernet switch
instead of to the 1G port on the COM400.
If the Meraki router is connected to the 1G port on the COM400, do not connect managed
ethernet switches to the Meraki router as the switch may send the IGMP Join and Query
request through the router to the COM400. This will then trigger the 1G port as a dynamic
router which will flood the Meraki with multicast traffic and prevent remote management. Any
devices downstream from the switch must also not send any IGMP Queries as well.
Background
IGMP Protocol – "10 Thousand Foot View"
When an end device is tuned to receive an IP video stream via multicast it will send an IGMP
Join request to the switch. The switch will then route the requested multicast stream to that
end device.
The Ethernet switch will then send occasional IGMP Query
request packets asking all the end devices to send another
IGMP Join request. If an IGMP Join request is not sent, the
switch will drop that end device from the IGMP group.
Technicolor recommends ports used for Managed Ethernet
switches be set as router port manually, however this
might not be required if the switch receives an IGMP Query
packet.
In a single COM3000 chassis system, normally the COM400
is the only IGMP Querier in the network so IGMP queries
are only transmitted out of the COM3000. But in situations
with more complicated multicast routing, there may be
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