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’s Manual
11
Manageable 8/9-Port Switch
IGMP Snooping & IP Multicast Filtering Continued...
If there is more than one router on the LAN performing IP multicasting, one of the routers is
elected ‘querier’ and assumes the reponsibility.
Based on the group membership information learned from the IGMP, a router can
determine which (if any) multicast traffic needs to be forwarded to each of its ‘leaf’
sub-networks. Multicast routers use this information, along with a multicast routing
protocol, to support IP multicasting across the Internet.
Routing switches support IP Multicast Filtering by:
- Passively snooping on the IGMP Query and IGMP Report packets transferred
between IP Multicast Routers and IP Multicast host groups to learn about IP
Multicast group members, and
- Actively sending IGMP Query messages to solicit IP Multicast group members.
The purpose of IP multicast filtering is to optimize a switched network’s performance, so
multicast packets will only be forwarded to those ports containing multicast group hosts
members and routers instead of flooding to all ports in the subnet (VLAN).
Routing switches with IP multicast filtering/switching capability not only run passively
monitor IGMP Query and Report messages, DVMRP Probe messages, PIM, and MOSPF Hello
messages; they also actively send IGMP Query messages to learn locations of multicast
routers and member hosts in multicast groups within each VLAN.
Note, however, IGMP neither alters nor routes any IP multicast packets. Since IGMP
is not concerned with the delivery of IP multicast packets across sub-networks, an
external IP multicast router is needed if IP multicast packets have to be routed
across different sub-networks.
SWITCH MANAGEMENT
Administration Console Via RS-232 Console Port:
The switch provides an on board serial port, which allows the switch to be configured via a
directly connected terminal or a Telnet session.
Web-Based Browser Interface:
The switch also boasts a point-and-click browser-based interface that lets users access full
switch configuration and functionality from a Netscape or Internet Explorer browser.
External SNMP-Based Network Management:
The switch can also be configured via SNMP.
For more information on switch management, please refer to the "Switch Management" section.