9.1.4.
Understand the working mechanism of IGMP Snooping
Conventional query and specific queries
IGMP will send all the hosts and routers in the network common set of query message,In Command to
query the network segment what IP multicast address is 224.0.0.1 multicast groups.After receiving the
IGMP universal set is the query message, switch the query message to the all port forwarding out
within a VLAN, and receiving port of the newspaper article to do the following:
If the port is already in routing connection port list, timer is reset to its aging.
If the port is not in routing connections list, then add it to the list of routing connectors, and start the
aging time.
After receive IGMP‘s common set of query message, multicast equipment will be switched to all
members of the port their aging timer,timer for configuration of IGMP query message to the longest
response time,When the timer timeout, argues that the port no more members to receive multicast
stream,multicast equipment will turn the port from the IGMP Snooping published.
Report the membership
The following case,The host will report to the IGMP inquirers IGMP membership to send a message:
When IP multicast group members of the host after receiving the IGMP query message,IGMP
membership report will reply message.
If the host IP to join a multicast group,It will take the initiative to send IGMP inquirers IGMP
membership report message to declare to join the IP multicast group.
IGMP membership after receiving the report message,Switch it to all routing within a VLAN connection
port forwarding to go out,
From the analysis of the message in the host IP multicast group address to join,and receiving port of
the newspaper article to do the following:
If there is no corresponding turned this IP multicast group published items,create the forwarding table
entries,add the port as members of the dynamic port to a port in the list,and start the aging timer;
If there are corresponding to the IP multicast forwarding table entries,but the output port does not
contain the list of ports,then the port as a dynamic member port is added to the list of ports,and start
the aging timer;
If there are corresponding to the IP multicast forwarding table entries,And the dynamic member port
already contains the list of ports,then aging timer is reset.
9.1.5.
Leave the multicast group
For the IGMP V2,when the host left the IP multicast group, IGMP leave group by sending a
message,in Command to inform the multicast router left an IP multicast group.When the switch from
one port on dynamic members receive IGMP leave group message,Switches will deal with it according
to whether launched immediately leave accordingly.If the switch opens the leave immediately, the port
is removed from the multicast table,If does not start to leave immediately, send a specific set of query
message,If have not received the report within the timeout message, will be the port is removed from
the multicast table.If you remove the port after the multicast group members have no port, switch to
routing port forwarding to leave a message.
9.1.6.
Understand IGMP Profiles
