xStack DES-6500 Modular Layer 3 Chassis Ethernet Switch CLI Manual
18
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 IGMP is also used to periodically check the multicast group for members that are no longer active.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 DES-6500 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
[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]}
{ipif <ipif_name 12>}
{group <group> | ipif <ipif_name 12>}
config igmp
show igmp
show igmp group
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> |
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