Friday, August 3, 2018

Multicast Problems

The developers here are starting to work with a multicast protocol implementation in one of our products per a customer request. I have two subnets, one for static hosts/servers and one for user desktops/laptops, etc, with a SonicWall routing between them and to the public internet. The developers need multicast traffic from one subnet to reach the other.

Multicast support is disabled by default on this SonicWall. But, it looks like all that's needed to enable is to check a box in the Firewall Settings and check a box on each of the relevant interfaces - easy enough.

And as soon as I did, the network ground to a near halt. I am not sure of the exact symptoms, but it took about 10 minutes to be able to bring up the web admin interface on the Sonicwall so I could get those boxes unchecked again.

I'm a sysadmin in a one-man shop, so while I have a baseline competency with networking, I don't know enough about multicast as a technology to figure out what went wrong.

Is there any obvious textbook cause why this would have happened? Doesn't need to be Sonicwall-specific (click this button then that one), but conceptually, what happened?



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