Multicast routing and IGMP

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Multicast routing and IGMP

Hi All,


I work for a pharma/nhs company that has a Meraki full stack and high end MS350's throughout.


We have a recently had some new patient monitoring devices installed that "require multicast".


This is literally the only instruction I had!  I remember installing multicast for IPTV in the past but it was only ever a tick box enable setting from memory.


I have enabled multicast routing on the neccessary VLAN that operate these devices but I'm now getting shouted at by the dashboard that no renevous point has been configured and multicast normally requires 2 interfaces not 1 etc.


Sorry I can't be more specific but can someone recommend to me what I need to do do to satisfy the requirements of "requires multicast".


I'm not sure what a rendevous point is




2 Replies 2
Here to help

So we just found out from Meraki support that our network is flooded with thousands of multicast packets - presumably since turning on Multicast routing on this one VLAN.


Their suggestion was to disabled SSDP on the windows hosts or create a access control list to block multicasts from other subnets!?


It is strongly recommended to block SSDP (Simple Service Discovery Protocol) traffic when Multicast Routing is enabled. 


Will simply enabling a renevous point fix this?


Our core switches often crash every few weeks and are cured by a reboot- I can only assume they are overwhelmed by multicast and routing tables fill up and clear once rebooted?


I don't have a lot of experience with multicast, but my understanding is that you only need multicast routing if you are routing multicast traffic between two or more networks.  If everything is on a single LAN you just need IGMP Snooping and and IGMP Querier.


I do have an application on one of our networks that relies on multicast, all I did for that network was to create an interface on the switch closest to the multicast source and under Multicast Routing I selected "Enable IGMP Snooping Querier", then under Switch Settings I have "IGMP Snooping" Enabled and "Flood unknown multicast traffic" disabled.


Here is some information from the Meraki documentation about multicast support:  Multicast support - Cisco Meraki


And this community post was very helpful:




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