HP VPN Firewall Appliances Network Management Configuration Guide

585
Ste
p
Command Remarks
3. Configure the interface to discard any
IGMP message that does not carry the
Router-Alert option.
igmp require-router-alert
By default, the device does not
check the Router-Alert option.
4. Enable insertion of the Router-Alert
option into IGMP messages.
igmp send-router-alert
By default, IGMP messages carry
the Router-Alert option.
Configuring IGMP query and response parameters
On startup, the IGMP querier sends IGMP general queries at the startup query interval, which is
one-quarter of the IGMP general query interval. The number of queries, or the startup query count, is user
configurable.
After startup, the IGMP querier periodically sends IGMP general queries at the IGMP general query
interval to check for multicast group members on the network. You can modify the IGMP general query
interval based on actual condition of the network.
The IGMPv2 querier sends IGMP group-specific queries at the IGMP last-member query interval when it
receives an IGMP leave message. The IGMPv3 querier sends IGMP group-and-source-specific queries at
the IGMP last-member query interval when it receives a multicast group and multicast mapping change
report. The number of queries, or the last-member query count, equals the robustness variable—the
maximum number of packet retransmissions.
A multicast listening host starts a delay timer for each multicast group it has joined when it receives an
IGMP query (general query, group-specific query, or group-and-source-specific query). The timer is
initialized to a random value in the range of 0 to the maximum response time derived in the IGMP query.
When the timer value decreases to 0, the host sends an IGMP report to the corresponding multicast
group.
To speed up the response of hosts to IGMP queries and avoid simultaneous timer expirations causing
IGMP report traffic bursts, you must correctly set the maximum response time.
• For IGMP general queries, the maximum response time is set by the max-response-time command.
• For IGMP group-specific queries and IGMP group-and-source-specific queries, the maximum
response time equals the IGMP last-member query interval.
When multiple multicast routers exist on the same subnet, the IGMP querier is responsible for sending
IGMP queries. If a non-querier router receives no IGMP query from the querier when the other querier
present interval expires, it considers that the querier as having failed and starts a new querier election.
Otherwise, the non-querier router resets the other querier present timer.
When you configure IGMP query and response parameters, follow these guidelines:
• To avoid frequent IGMP querier changes, set the other querier present interval greater than the
IGMP general query interval.
• To avoid incorrect multicast group member removals, set the IGMP general query interval greater
than the maximum response time for IGMP general queries.
• The configurations of the maximum response time for IGMP general queries, the IGMP last member
query interval and the IGMP other querier present interval are effective only for IGMPv2 and
IGMPv3.
To configure IGMP query and response parameters globally:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A