When the number of IPv6 multicast groups that can be joined on a port reaches the maximum
number configured, the system deletes all the forwarding entries persistent to that port from the
MLD Snooping forwarding table, and the hosts on this port need to join IPv6 multicast groups
If you have configured static or simulated joining on a port, however, when the number of IPv6
multicast groups on the port exceeds the configured threshold, the system deletes all the
forwarding entries persistent to that port from the MLD Snooping forwarding table and applies the
static or simulated joining again, until the number of IPv6 multicast groups joined by the port comes
back within the configured threshold.
Configuring IPv6 Multicast Group Replacement
For some special reasons, the number of IPv6 multicast groups passing through a switch or port may
exceed the number configured for the switch or the port. In addition, in some specific applications, an
IPv6 multicast group newly joined on the switch needs to replace an existing IPv6 multicast group
automatically. A typical example is "channel switching", namely, by joining the new multicast group, a
user automatically switches from the current IPv6 multicast group to the new one.
To address this situation, you can enable the IPv6 multicast group replacement function on the switch or
certain ports. When the number of IPv6 multicast groups a switch or a port has joined exceeds the limit.
If the IPv6 multicast group replacement is enabled, the newly joined IPv6 multicast group
automatically replaces an existing IPv6 multicast group with the lowest IPv6 address.
If the IPv6 multicast group replacement is not enabled, new MLD reports will be automatically
Configuring IPv6 multicast group replacement globally
Follow these steps to configure IPv6 multicast group replacement globally:
Enter system view
Enter MLD Snooping view
Enable IPv6 multicast group
Use the command...
overflow-replace [ vlan
Disabled by default