Internal Querier Processing; Querier Election For One Active Querier - Cisco ASR 9000 Series Configuration Manual

Internal Querier
Configuration Command
internal-querier timer expiry
Note
internal-querier version
You can disable the internal querier (using the no form of the internal-querier command) without removing
any other internal querier commands. The additional internal querier commands are ignored in that case.
The scope for the internal-querier command is per bridge domain. If the command appears in profiles attached
to ports, it has no effect.

Internal Querier Processing

When the internal querier is the elected querier in the domain, it solicits membership reports by sending IGMP
general queries at the interval specified by the internal-querier query-interval command on every active
port in the bridge domain. The internal querier sends IGMPv3 queries by default. You can configure it to send
IGMPv2 messages instead using the internal-querier version command.
The local IGMP snooping process responds to the internal querier's general queries. In particular, the IGMPv3
proxy (if enabled) generates a current-state report and forwards it to all mrouters. For IGMPv2 or when the
IGMPv3 proxy is disabled, IGMP snooping generates current-state reports for static group state only.
The queries are sent from the address you configure for IGMP snooping using the system-ip-address command.
The queries include the maximum response time configured with the internal-querier max-response-time
command.
The internal-querier robustness-variable and internal-querier query-interval commands configure values
for both IGMPv2 and IGMPv3 processing.

Querier Election for One Active Querier

A bridge domain can have only one active querier at a time. If the internal-querier receives queries from
another querier in a bridge domain, it performs querier election. The lowest IP address wins. If the internal
querier is the election loser, IGMP snooping starts a timer with the value set by the internal-querier timer
expiry command. If this timer expires before another query is received from the election winner, the internal
querier becomes the active querier.
Note The default internal-querier timer expiry command value is derived from the values of other configuration
options, as described in
configure a different value to override the default calculation.
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 6.0.x
20
This is the Other Querier Present Interval as
defined in RFC-3376, Section 8.5.
Table 7: Internal Querier Default Configuration Values, on page
Implementing Layer-2 Multicast with IGMP Snooping
Default Value
125 (seconds):
robustness-variable * query-interval +
½(max-response-time)
For example, using the default values for all
components:
(2 * 60) + ½ (10) = 125
3
19. You can