How Mld Snooping Works - HP 6125XLG Ip Multicast Configuration Manual

NOTE:
In MLD snooping, only dynamic ports age out. Static ports never age out.

How MLD snooping works

The ports in this section are dynamic ports. For information about how to configure and remove static
ports, see "Configuring static
MLD messages include general query, MLD report, and done message. An MLD snooping-enabled
switch performs differently depending on the MLD message.
General query
To check for the existence of IPv6 multicast group members, the MLD querier periodically sends MLD
general queries to all hosts and routers on the local subnet. All these hosts and routers are identified by
the address FF02::1.
After receiving an MLD general query, the switch forwards the query to all ports in the VLAN except the
port that received the query. The switch also performs one of the following actions:
If the receiving port is a dynamic router port in the router port list, the switch restarts the aging timer
•
for the router port.
If the receiving port does not exist in the router port list, the switch adds the port to the router port
•
list. It also starts an aging timer for the port.
MLD report
A host sends an MLD report to the MLD querier for the following purposes:
• Responds to queries if the host is an IPv6 multicast group member.
Applies for an IPv6 multicast group membership.
•
After receiving an MLD report, the switch forwards it through all the router ports in the VLAN, resolves the
IPv6 address of the reported IPv6 multicast group, and looks up the forwarding table for a matching
entry:
If no match is found, the switch creates a forwarding entry for the group and adds the receiving port
•
as an outgoing interface to the forwarding entry. It also marks the receiving port as a dynamic
member port and starts an aging timer for the port.
If a match is found but the receiving port is not in the forwarding entry, the switch adds the receiving
•
port as an outgoing interface to the forwarding entry. It also marks the receiving port as a dynamic
member port and starts an aging timer for the port.
• If a match is found and the receiving port is in the forwarding entry, the switch restarts the aging
timer for the port.
In an application with an IPv6 multicast group filter configured on an MLD snooping-enabled switch,
when a user requests a multicast program, the user's host initiates an MLD report. After receiving this
report message, the switch resolves the IPv6 multicast group address in the report and performs an ACL
filtering on the report. If the report passes the ACL filtering, the switch creates an MLD snooping
forwarding entry for the IPv6 multicast group with the receiving port as an outgoing interface. Otherwise,
the switch drops this report message, in which case, which means the receiver does not successfully join
the IPv6 multicast group and cannot retrieve the program.
A switch does not forward an MLD report through a non-router port because of the IGMP report
suppression mechanism. Assuming the switch forwards a report through a member port, the attached
ports."
215