Administrator’s Handbook
140
You can set the following options:
IGMP Snooping – Enables the NVG599 to “listen in” to IGMP traffic. The NVG599 discovers multicast group
membership for the purpose of restricting multicast transmissions to only those ports which have requested
them. This restriction helps to reduce overall network traffic from streaming media and other bandwidth-
intensive IP multicast applications.
Robustness – A way of indicating how sensitive to lost packets the network is. IGMP can recover from
robustness minus 1 lost IGMP packet. The default value is 2.
Query Interval – The amount of time in seconds between IGMP General Query messages sent by the querier
gateway. The default query interval is 125 seconds.
Query Response Interval – The maximum amount of time in tenths of a second that the IGMP gateway waits
to receive a response to a General Query message. The default query response interval is 10 seconds and
must be less than the query interval.
Unsolicited Report Interval – The amount of time in seconds between repetitions of a particular computer’s
initial report of membership in a group. The default unsolicited report interval is 10 seconds.
Querier Version – Version of the IGMP querier: version 1, version 2, or version 3. If you know you will be
communicating with other hosts that are limited to v1 or v2, for backward compatibility, select accordingly;
otherwise, allow the default v3.
Last Member Query Interval – The amount of time in tenths of a second that the IGMP gateway waits to
receive a response to a Group-Specific Query message. The last member query interval is also the amount of
time in seconds between successive Group-Specific Query messages. The default last member query interval
is 1 second (10 deci-seconds).
Last Member Query Count – The number of Group-Specific Query messages sent before the gateway
assumes that there are no members of the host group being queried on this interface. The default last mem-
ber query count is 2.
Fast Leave – Set to off by default, fast leave enables a non-standard expedited leave mechanism. The querier
keeps track of which client is requesting which channel by IP address. When a leave message is received, the
querier can check its internal table to see if there are any more clients on this group. If there are none, it
immediately sends an IGMP leave message to the upstream querier.
Log Enable – If set to on, all IGMP messages on both the LAN and the WAN will be logged.
Wireless Multicast to Unicast conversion – Only available if IGMP snooping is enabled. If set to on, the gate-
way replaces the multicast MAC address with the physical MAC address of the wireless client. If there is
more than one wireless client interested in the same multicast group, the gateway will revert to multicasting
the stream immediately. When one or more wireless clients leave a group, and the gateway determines that
only a single wireless client is interested in the stream, it will once again unicast the stream.
set ip igmp querier-version [ 1 | 2 | 3 ]
Sets the IGMP querier version: version 1, version 2, or version 3. If you know you will be communicating with
other hosts that are limited to v1, for backward compatibility, select 1; otherwise, allow the default 3.
set ip igmp robustness value
Sets IGMP robustness range: 2 – 255. The default is 2.
set ip igmp query-interval value
Sets the query-interval range: 10 seconds – 600 seconds. The default is 125 seconds.
NOTE:
IGMP querier version is relevant only if the gateway is configured for IGMP forwarding. If any IGMP v1 rout-
ers are present on the subnet, the querier must use IGMP v1. The use of IGMP v1 must be administratively
configured, since there is no reliable way of dynamically determining whether IGMP v1 routers are present
on a network. IGMP forwarding is enabled per the IP profile and the WAN connection profile.
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