AT-S63 Management Software Features Guide
Section III: Snooping Protocols
199
Overview
IPv4 routers use IGMP to create lists of nodes that are members of
multicast groups. (A multicast group is a group of end nodes that want to
receive multicast packets from a multicast application.) The router creates
a multicast membership list by periodically sending out queries to the local
area networks connected to its ports.
A node wanting to become a member of a multicast group responds to a
query by sending a
report
. A report indicates an end node’s desire to
become a member of a multicast group. Nodes that join a multicast group
are referred to as
host nodes
. After becoming a member of a multicast
group, a host node must continue to periodically issue reports to remain a
member.
After the router has received a report from a host node, it notes the
multicast group that the host node wants to join and the port on the router
where the node is located. Any multicast packets belonging to that
multicast group are then forwarded by the router out the port. If a particular
port on the router has no nodes that want to be members of multicast
groups, the router does not send multicast packets out the port. This
improves network performance by restricting multicast packets only to
router ports where host nodes are located.
There are three versions of IGMP — versions 1, 2, and 3. One of the
differences between the versions is how a host node signals that it no
longer wants to be a member of a multicast group. In version 1 it stops
sending reports. If a router does not receive a report from a host node after
a predefined length of time, referred to as a
time-out value
, it assumes that
the host node no longer wants to receive multicast frames, and removes it
from the membership list of the multicast group.
In version 2 a host node exits from a multicast group by sending a
leave
request
. After receiving a leave request from a host node, the router
removes the node from appropriate membership list. The router also stops
sending multicast packets out the port to which the node is connected if it
determines there are no further host nodes on the port.
Version 3 adds the ability of host nodes to join or leave specific sources in
a multicast group.
The IGMP snooping feature on the AT-9400 Switch supports all three
versions of IGMP. The switch monitors the flow of queries from routers
and reports and leave messages from host nodes to build its own multicast
membership lists. It uses the lists to forward multicast packets only to
switch ports where there are host nodes that are members of multicast
groups. This improves switch performance and network security by
restricting the flow of multicast packets only to those switch ports
connected to host nodes.
Содержание AT-S63
Страница 14: ...Figures 14 ...
Страница 18: ...Tables 18 ...
Страница 28: ...28 Section I Basic Operations ...
Страница 58: ...Chapter 1 Overview 58 ...
Страница 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Страница 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Страница 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Страница 116: ...116 Section II Advanced Operations ...
Страница 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Страница 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Страница 196: ...196 Section III Snooping Protocols ...
Страница 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Страница 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Страница 218: ...218 Section IV SNMPv3 ...
Страница 234: ...234 Section V Spanning Tree Protocols ...
Страница 268: ...268 Section VI Virtual LANs ...
Страница 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Страница 320: ...320 Section VII Internet Protocol Routing ...
Страница 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Страница 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Страница 372: ...372 Section VIII Port Security ...
Страница 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Страница 404: ...404 Section IX Management Security ...
Страница 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Страница 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Страница 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Страница 504: ...Appendix B SNMPv3 Configuration Examples 504 Security Model Security Level Storage Type SNMPv3 Parameters Continued ...
Страница 532: ...Appendix D MIB Objects 532 ...