xStack DGS-3612G Layer 3 Gigabit Ethernet Managed Switch CLI Manual
19
IGMP C
OMMANDS
(I
NCLUDING
IGMP
V
3)
IGMP or Internet Group Management Protocol is a protocol implemented by systems utilizing IPv4 to collect the membership
information needed by the multicast routing protocol through various query messages sent out from the router or switch. Computers
and network devices that want to receive multicast transmissions need to inform nearby routers that they will become members of a
multicast group. The
Internet Group Management Protocol (IGMP
) is used to communicate this information. IGMP is also used to
periodically check the multicast group for members that are no longer active.
In the case where there is more than one multicast router on a subnetwork, one router is elected as the ‘querier’. This router then
keeps track of the membership of the multicast groups that have active members. The information received from IGMP is then used to
determine if multicast packets should be forwarded to a given subnetwork or not. The router can check, using IGMP, to see if there is
at least one member of a multicast group on a given subnetwork. If there are no members on a subnetwork, packets will not be
forwarded to that subnetwork.
The current release of the xStack DGS-3612G now implements IGMPv3. Improvements of IGMPv3 over version 2 include:
•
The introduction of the
SSM
or
Source Specific Multicast
. In previous versions of IGMP, the host would receive all packets sent
to the multicast group. Now, a host will receive packets only from a specific source or sources. This is done through the
implementation of
include
and
exclude
filters used to accept or deny traffic from these specific sources.
•
In IGMPv2, Membership reports could contain only one multicast group whereas in v3, these reports can contain multiple
multicast groups.
•
Leaving a multicast group could only be accomplished using a specific leave message in v2. In v3, leaving a multicast group is
done through a Membership report which includes a block message in the group report packet.
•
For version 2, the host could respond to either a group query but in version 3, the host is now capable to answer queries specific
to the group and the source.
IGMPv3 is backwards compatible with other versions of IGMP and all IGMP protocols must be used in conjunction with PIM-DM or
DVMRP for optimal use.
The IGMP commands in the Command Line Interface (CLI) are listed (along with the appropriate parameters) in the following table.
Command Parameters
config igmp
[ipif <ipif_name 12> | all] {version <value 1-3> | query_interval <sec
1-31744> | max_response_time <sec 1-25> | robustness_variable
<value 1-255> | last_member_query_interval <value 1-25> | state
[enable | disable]}
show igmp
{ipif <ipif_name 12>}
show igmp group
{group <group> | ipif <ipif_name 12>}
Each command is listed, in detail, in the following sections.
config igmp
Purpose
Used to configure IGMP on the Switch.
Syntax
config igmp [ipif <ipif_name 12> | all] {version <value 1-3> |
query_interval <sec 1-31744> | max_response_time <sec 1-25> |
robustness_variable <value 1-255> | last_member_query_interval
<value 1-25> | state [enable | disable]}
Description
This command allows users to configure IGMP on the Switch.
Parameters
<ipif_name 12>
−
The name of the IP interface for which to configure
IGMP.
all
−
Specifies all the IP interfaces on the Switch.
version <value 1-3>
−
Select the IGMP version number.
query_interval <sec 1-31744>
−
The time in seconds between general
query transmissions, in seconds.
max_response_time <sec 1-25>
−
Enter the maximum time in seconds
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