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211
CONFIG Commands
IGMP Settings
Multicasting
is a method for transmitting large amounts of information to many, but not
all, computers over an internet. One common use is to distribute real time voice, video,
and data services to the set of computers which have joined a distributed conference.
Other uses include updating the address books of mobile computer users in the field, or
sending out company newsletters to a distribution list.
Since a router should not be used as a passive forwarding device, Motorola Netopia®
Gateways use a protocol for forwarding multicasting: Internet Group Management Protocol
(IGMP).
Motorola Netopia® Gateways support IGMP Version 1, Version 2, or, beginning with Motor-
ola Netopia® Firmware Version 7.7, Version 3.
IGMP “Snooping”
is a feature of Ethernet layer 2 switches that “listens in” on the IGMP
conversation between computers and multicast routers. Through this process, it builds a
database of where the multicast routers reside by noting IGMP general queries used in the
querier selection process and by listening to other router protocols.
From the host point of view, the snooping function listens at a port level for an IGMP
report. The switch then processes the IGMP report and starts forwarding the relevant mul-
ticast stream onto the host's port. When the switch receives an IGMP
leave
message, it
processes the leave message, and if appropriate stops the multicast stream to that partic-
ular port. Basically, customer IGMP messages although processed by the switch are also
sent to the multicast routers.
In order for IGMP snooping to function with IGMP Version 3, it must always track the full
source filter state of each host on each group, as was previously done with Version 2 only
when
Fast Leave
support was enabled.
IGMP Version 3
supports:
IGMP Source Filtering: the ability for group memberships to incorporate source address fil-
tering. This allows “Source-Specific Multicast” (SSM). By adding source filtering, a Gateway
that proxies IGMP can more selectively join the specific multicast group for which there are
interested LAN multicast receivers.
These features require no user configuration on the Gateway.
You can set the following options:
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212
IGMP Snooping
– enables the Motorola Netopia® Gateway to “listen in” to IGMP traf-
fic. The Gateway discovers multicast group membership for the purpose of restricting
multicast transmissions to only those ports which have requested them. This 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 mes-
sages 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 router 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
– select a 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.
NOTE:
IGMP Querier version is relevant only if the router is configured for IGMP for-
warding. If any IGMP v1 routers 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 IP Profile and WAN
Connection Profile.
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 mem-
ber 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 que-
ried on this interface. The default last member 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
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213
CONFIG Commands
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 Gateway replaces the multicast MAC-address with the physi-
cal MAC-address of the wireless client. If there is more than one wireless client inter-
ested in the same multicast group, the router will revert to multicasting the stream
immediately. When one or more wireless clients leave a group, and the router deter-
mines that only a single wireless client is interested in the stream, it will once again uni-
cast the stream.
set igmp snooping [ off | on ]
Enables IGMP Snooping.
set igmp robustness
value
Sets IGMP robustness range: from 2 – 255. The default is 2.
set igmp query-intvl
value
Sets the query-interval range: from 10 seconds – 600 seconds, The default is 125 sec-
onds.
set igmp query-response-intvl
value
Sets the query-response interval range: from 5 deci-seconds (tenths of a second) – 255
deci-seconds. The default is 100 deci-seconds.
set igmp unsol-report-intvl
value
Sets the 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 is 10 seconds.
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214
set igmp 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 igmp last-member-query-intvl
value
Sets the 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 is 1 second (10 deci-seconds).
set igmp last-member-query-count
value
Sets the 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 is 2.
set igmp fast-leave [ off | on ]
Sets fast leave on or off. 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.
set igmp wireless-m2u [ on | off ]
This command allows you enable or disable wireless multicast-to-unicast if
igmp snooping
is set to
on
.
set igmp log-enable [ on | off ]
If set to
on
, all IGMP messages on both the LAN and the WAN will be logged. Default is
off
.
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215
CONFIG Commands
IP Settings
You can use the command line interface to specify whether TCP/IP is enabled, identify a
default Gateway, and to enter TCP/IP settings for the Motorola Netopia® Gateway LAN and
WAN ports.
NOTE:
For the DSL platform you must identify the virtual PPP interface [
vccn
], a num-
ber from 1 to 8.
Common Settings
set ip option { on | off }
Enables or disables TCP/IP services in the Motorola Netopia® Gateway. You must enable
TCP/IP services before you can enter other TCP/IP settings for the Motorola Netopia®
Gateway. If you turn off TCP/IP services and save the new configuration, the Motorola
Netopia® Gateway clears its TCP/IP settings.
ARP Timeout Settings
set ip arp-timeout [ 60 ... 6000 ]
Sets the timeout value for ARP timeout. Default = 600 secs (10 mins); range = 60 secs -
6000 secs (1–100 mins).
DSL Settings
set ip dsl vccn address
ip_address
Assigns an IP address to the virtual circuit. Enter 0.0.0.0 if you want the virtual circuit to
obtain its IP address from a remote DHCP server.

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