NETGEAR S3300-28X (GS728TX) 24x1GE - Инструкция по эксплуатации - Страница 171

Configuring Switching 

171

 S3300 Smart Managed Pro Switch

Auto-Video

Use this screen to configure the Auto-Video parameters.



To configure Auto-Video:

1. 

Select 

Switching



>

 Multicast 

>

 Auto-Video

.

2. 

Select one of the following radio buttons:

•

Select the 

Disable

 radio button to globally disable Auto-Video administrative mode 

for the switch.

•

Select the 

Enable

 radio button to globally enable Auto-Video administrative mode for 

the switch.

The Auto-Video VLAN field shows the number of Auto-configured IGMP snooping 
VLANs.

3. 

Click the 

Apply

 button. 

IGMP Snooping 

Internet Group Management Protocol (IGMP) snooping is a feature that allows a switch to 
forward multicast traffic intelligently on the switch. Multicast IP traffic is traffic that 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 has any 
interest in receiving the packet. While nodes rarely incur any processing overhead to filter 
packets addressed to unrequested group addresses, they are unable to transmit new 
packets onto the shared media for the period of time 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.

Allowing switches to snoop IGMP packets is a creative effort to solve this problem. The 
switch uses the information in the IGMP packets as they are being forwarded throughout the 
network to determine which segments should receive packets directed to the group address.