Alexandr, I agree with what Tony has said. We have dealt with these messages for at least 3 or 4 years. Only happens where you have a lot of vlans /vmans and the users are either true Mcast for IPTV or video/ lan leaking UPNP Mcast traffic into core/ lots of routers talking OSPF/ EIGRP/ ect. We spent a good 3 or 4 months with GTAC to only determine it was indeed the hardware and software tables not being in sync. As a rule we disable IGMP snooping on all core or aggregation switches so we have assurances Mcast will be forwarded correctly. Mcast table size has always been a concern and a problem we have had to deal with. To many people only associate Mcast with IPTV and forget about routing protocols are 100 % dependent on healthy Mcast in your system. Good luck
As you mentioned, it looks like the table is not full. As mentioned in the article, this is most likely a temporary hardware / software table sync issue. If the messages were only seen this one time, I would not worry about it. If the messages continue to be seen you would want to look into it further to see if the cause may be due to an EXOS code issue. At that point, if you have a support contract with Extreme, opening a case with GTAC would be advised for further assistance.