Default IGMP Configuration Problems On Juniper EX Switches

Having trouble with multicast on Juniper EX Switches? Read on –

Today I was troubleshooting a customer environment that had migrated from a HP Based Switching Infrastructure, to a Juniper EX Switching environment. The VOIP system (ESI) was having trouble “discovering” it’s phones. A wireshark tells the story;

As we can see, the phone is sending out a multicast frame to 01:30:4d:ff:ff:ff – This setup will fail on a Juniper switch because of the following default commands regarding IGMP:

protocols {
    igmp-snooping {
        vlan all;


This will enable IGMP-Snooping on all VLANS. By default IGMP Snooping on Juniper will drop all multicast frames not registered to a group, when it should be flooding instead. HP Switches will happily forward this traffic. To resolve this, disable IGMP-Snooping with:

delete protocols igmp-snooping


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