Virtual Secure Web Gateway

I deployed my two Symantec Web Gateway server on DMZ network for internet facing, these two servers are running in clustering and another interface is on LAN.  It is found that my firewall received a lot of deny IGMP traffic for reverse path check from DMZ network.  Why the Web Gateway need IGMP?  What happen if this traffic is blocked at firewall?

thx!

This traffic will not affect the way the Web Gateway functions, so you can safely block it. If you need the appliance to stop transmitting this traffic permanently, you can open a support case with this request and we will have you open a Remote Assistance case for this to be done.