ZyXEL Communications ZyXEL Dimension ES-3124-4F - Manual (Page 66)

ES-3100 Series Switch Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
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3. Right after the VLAN, you should add the IP domains to the related VLANs.
4. Since this GS-4024 works as an IGMP Router, you need to enable IGMP
V2 on the multicast ip interface (which is the dummy interface). Please
notice that since GS-4024 works here as an IGMP Router, you cannot
enable IGMP Snooping on the same time because IGMP Snooping is a L2
feature.