Meraki Switch with 2 Layer 3 Interface without routing

[mirueger]

Hi All we need 2 Interface with L3 Function because of Multicast. All Routing is down on the MX attached to the Switch. But at the Moment I activate the second L3 Interface on the Switch the Switch starts routing between them. Is there a way to blick this? because ACL on Switch will block even traffic coming from the Firewall 😞

[Karsten Iwen]

Do I understand you right that you want to route unicast on the MX and Multicast on the MS? That won't work, and if it did, it would open a can of worms.

This is a scenario where the MX as a routing device is likely not the best fit.

[ww^]

The switch only routes traffic that you send to it. If your clients use the mx as gateway the switch doesnt route that traffic

This behavior is not specific to meraki. Most other devices behave the same, and you would need something like vrf support

[Karsten Iwen]

Technically correct, but I would not accept something like that in my networks. It could be addressed by chance or even intentionally and bypass the firewall controls.

This is a workaround that screams, "I will make trouble when you don't think about it any more".

[Philip D'Ath · Accepted solution]

Going sideways, have a read of this post going into a much deeper dive about multicast routing, PIM and IGMP queriers. It might impact your decisions.

https://community.meraki.com/t5/Switching/Multicast-Basic-s/m-p/25867/highlight/true#M2125

[mirueger]

Hi Philip, Thanks for the Link. It solved the way we addressed the Problem. We had the routing on the MX as designed. After a request of Multicast we needed 2 Interface on the Switch. And just as Karstenl says don't like the Idea that the switch is tarting routing also. Thanks for the Link.