386
Step
Command
Remarks
messages.
Configuring Router-Alert option handling methods on an interface
Step
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter interface view.
interface
interface-type
interface-number
N/A
3.
Configure the interface to
discard any MLD message
without the Router-Alert
option.
mld require-router-alert
By default, the device does not
examine MLD messages for the
Router-Alert option.
4.
Enable the insertion of the
Router-Alert option into MLD
messages.
mld send-router-alert
By default, MLD messages carry
the Router-Alert option.
Configuring MLD query and response parameters
On startup, the MLD querier sends MLD general queries at the startup query interval, which is
one-quarter of the MLD query interval. The number of queries, or the startup query count, is user
configurable.
After startup, the MLD querier periodically sends MLD general queries at the MLD query interval to
examine for IPv6 multicast group members on the network. You can modify the query interval based
on the actual condition of the network.
The MLDv1 querier sends MLD multicast-address-specific queries at the MLD last listener query
interval when it receives an MLD done message. The MLDv2 querier sends MLD
multicast-address-and-source-specific queries at the MLD last listener query interval when it
receives a multicast group and multicast source mapping change report. The number of queries, or
the last listener query count, equals the robustness variable, which is the maximum number of
packet retransmissions.
A multicast listening host starts a timer for each IPv6 multicast group that it has joined when it
receives an MLD query (general query, multicast-address-specific query, or
multicast-address-and-source-specific query). The timer is initialized to a random value in the range
of 0 to the maximum response delay advertised in the MLD query message. When the timer
decreases to 0, the host sends an MLD membership report message to the IPv6 multicast group.
To speed up the response of hosts to MLD queries and avoid simultaneous timer expirations causing
MLD report traffic bursts, you must properly set the maximum response delay.
•
For MLD general queries, the maximum response delay is set by the
max-response-time
command.
•
For MLD multicast-address-specific query and multicast-address-and-source-specific query
messages, the maximum response delay equals the last listener query interval.
When multiple multicast routers exist on the same subnet, the MLD querier is responsible for
sending MLD query messages. If a non-querier router receives no MLD query from the querier when
the other querier present interval expires, it considers the querier as having failed and starts a new
querier election. Otherwise, the non-querier resets the other querier present timer.
Configuration guidelines
•
To avoid frequent MLD querier changes, set the other querier present interval greater than the
MLD query interval.
