3Com S7902E, Configuration Manual

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1-15
To do… Use the command… Remarks
Configure the interface to
discard any MLD message
without the Router-Alert option
require-router-alert
Optional
By default, the device does not
check MLD messages for the
Router-Alert option.
Enable the insertion of the
Router-Alert option into MLD
messages
send-router-alert
Optional
By default, MLD messages
carry the Router-Alert option.
Configuring the Router-Alert option on an interface
Follow these steps to configure the Router-Alert option on an interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter interface view
interface interface-type
interface-number
—
Configure the interface to
discard any MLD message
without the Router-Alert option
mld require-router-alert
Optional
By default, the device does not
check MLD messages for the
Router-Alert option.
Enable the insertion of the
Router-Alert option into MLD
messages
mld send-router-alert
Optional
By default, MLD messages
carry the Router-Alert option.
Configuring MLD Query and Response Parameters
On startup, the MLD querier sends “startup query count” MLD general queries at the “startup query
interval”, which is 1/4 of the “MLD query interval”.
The MLD querier periodically sends MLD general queries at the “MLD query interval” to determine
whether any IPv6 multicast group member exists on the network. You can modify the query interval
based on the actual condition of the network.
Upon receiving an MLD done message, the MLD querier sends “last listener query count” MLD
multicast-address-specific queries at the “MLD last listener query interval”. MLD is robust to
“robustness variable minus 1” packet losses on a network. Therefore, a greater value of the robustness
variable makes the MLD querier “more robust”, but results in a longer IPv6 multicast group timeout time.
Upon receiving an MLD query (general query or multicast-address-specific query) message, a host
starts a timer for each IPv6 multicast group it has joined. The timer is initialized to a random value in the
range of 0 to the maximum response delay (the host obtains the maximum response delay from the
Maximum Response Delay field in the MLD query message it received). When the timer value drops to
0, the host sends an MLD membership report message to the corresponding IPv6 multicast group.
Proper setting of the maximum response delay of MLD query messages not only allows hosts to
respond to MLD query messages quickly, but also avoids bursts of MLD traffic on the network caused
by reports simultaneously sent by a large number of hosts when corresponding timers expire
simultaneously.