Netgear GSM4248P User Manual - Page 253

AV Line of Fully Managed Switches M4250 Series Main User Manual Table 65. MFDB statistics information Field Max MFDB Table Entries Most MFDB Entries Since Last Reset Current Entries Description The maximum number of entries that the multicast forwarding database table can hold. The largest number of entries that were present in the multicast forwarding database table since the last reset. This value is also known as the MFDB high-water mark. The current number of entries in the multicast forwarding database table. Internet Group Management Protocol snooping Internet Group Management Protocol (IGMP) snooping allows a switch to forward multicast traffic intelligently. Multicast IP traffic is destined to a host group. Host groups are identified by class D IP addresses, which range from 224.0.0.0 to 239.255.255.255. Based on the IGMP query and report messages, the switch forwards traffic only to the ports that request the multicast traffic. This prevents the switch from broadcasting the traffic to all ports and possibly affecting network performance. A traditional Ethernet network can be separated into different network segments to prevent placing too many devices onto the same shared media. Bridges and switches connect these segments. When a packet with a broadcast or multicast destination address is received, the switch forwards a copy into each of the remaining network segments in accordance with the IEEE MAC Bridge standard. Eventually, the packet is made accessible to all nodes connected to the network. This approach works well for broadcast packets that are intended to be seen or processed by all connected nodes. In the case of multicast packets, however, this approach could lead to less efficient use of network bandwidth, particularly when the packet is intended for only a small number of nodes. Packets are flooded into network segments where no node is receptive to the packet. While nodes rarely incur any processing overhead to filter packets addressed to unrequested group addresses, they cannot transmit new packets onto the shared media during the period that the multicast packet is flooded. The problem of wasting bandwidth is even worse when the LAN segment is not shared, for example in full-duplex links. Configure Switching Information 253 Main User Manual