3com 3031 Instruccion De Instalación
47
IGMP C
ONFIGURATION
IGMP Overview
Introduction to IGMP
IGMP (Internet Group Management Protocol) is a protocol in the TCP/IP suite
responsible for management of IP multicast members. It is used to establish and
maintain multicast membership between IP hosts and their directly connected
neighboring routers. The transmission and maintenance of membership
information among multicast routers, are completed by multicast routing
protocols. All the hosts participating in multicast must support IGMP.
responsible for management of IP multicast members. It is used to establish and
maintain multicast membership between IP hosts and their directly connected
neighboring routers. The transmission and maintenance of membership
information among multicast routers, are completed by multicast routing
protocols. All the hosts participating in multicast must support IGMP.
An IP multicast host can join or exit a multicast group at any time and any where.
There is no restriction on the total number of group members. A multicast router
needs not and cannot save the membership information of all the hosts. It only
checks the network segment connected with each interface by IGMP to see
whether there are receivers of a multicast group, namely group members. A host
only needs to save the information telling which multicast groups it joins.
There is no restriction on the total number of group members. A multicast router
needs not and cannot save the membership information of all the hosts. It only
checks the network segment connected with each interface by IGMP to see
whether there are receivers of a multicast group, namely group members. A host
only needs to save the information telling which multicast groups it joins.
IGMP is not symmetric between the host and the router. The host needs to reply,
as a group member, to IGMP query messages from the multicast router. The router
needs to send membership query messages periodically and to check if any host of
a specified group joins to its subnets based on the received response messages.
When the router receives a report that hosts have quitted the group, the router
will send a group-specific query (IGMP Version 2) to find out if this group still has a
group member.
as a group member, to IGMP query messages from the multicast router. The router
needs to send membership query messages periodically and to check if any host of
a specified group joins to its subnets based on the received response messages.
When the router receives a report that hosts have quitted the group, the router
will send a group-specific query (IGMP Version 2) to find out if this group still has a
group member.
Up until now, IGMP has three versions: IGMP Version 1 (defined by RFC1112),
IGMP Version 2 (defined by RFC2236) and IGMP Version 3. At present, IGMP
Version 2 is the most widely used version.
IGMP Version 2 (defined by RFC2236) and IGMP Version 3. At present, IGMP
Version 2 is the most widely used version.
IGMP Version 2 improvements on Version 1 include:
Querier selection mechanism on a shared network segment
A shared network segment is a network segment with multiple multicast routers.
In this case, all routers running IGMP on this network segment can receive the
membership report from hosts. Therefore, only one router is necessary to send
membership query messages. In this case, the querier selection mechanism is
required to specify a router as the querier.
In this case, all routers running IGMP on this network segment can receive the
membership report from hosts. Therefore, only one router is necessary to send
membership query messages. In this case, the querier selection mechanism is
required to specify a router as the querier.
IGMP Version 1 selects the querier by the multicast routing protocol, while IGMP
Version 2 decides on the multicast router with the lowest IP address as the querier.
Version 2 decides on the multicast router with the lowest IP address as the querier.