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Advanced Configuration and Management Guide
Upstream: Represents the direction from which a router receives multicast data packets. An upstream router is
a node that sends multicast packets.
Downstream: Represents the direction to which a router forwards multicast data packets. A downstream router
is a node that receives multicast packets from upstream transmissions.
Group Presence: Means that a multicast group has been learned from one of the directly connected interfaces.
Members of the multicast group are present on the router.
Intermediate nodes: Routers that are in the path between source routers and leaf routers.
Leaf nodes: Routers that do not have any downstream routers.
Multicast Tree: A unique tree is built for each source group (S,G) pair. A multicast tree is comprised of a root
node and one or more nodes that are leaf or intermediate nodes.
Changing Global IP Multicast Parameters
The following configurable parameters apply to PIM-DM, PIM-SM, and DVMRP.
• Internet Group Membership Protocol (IGMP) parameters – You can change the query interval, group
membership time, and maximum response time.
• Hardware forwarding of fragmented IP multicast packets – You can enable the routing switch to forward all
fragments of fragmented IP multicast packets in hardware.
Changing IGMP Parameters
IGMP allows HP routing switches to limit the multicast of IGMP packets to only those ports on the routing switch
that are identified as IP Multicast members. HP devices support IGMP versions 1 and 2.
The routing switch actively sends out host queries to identify IP Multicast groups on the network, inserts the group
information in an IGMP packet, and forwards the packet to IP Multicast neighbors.
The following parameters apply to PIM and DVMRP:
• IGMP query interval – Specifies how often the routing switch queries an interface for group membership.
Possible values are 1 – 3600. The default is 60.
• IGMP group membership time – Specifies how many seconds an IP Multicast group can remain on a routing
switch interface in the absence of a group report. Possible values are 1 – 7200. The default is 60.
• IGMP maximum response time – Specifies how many seconds the routing switch will wait for an IGMP
response from an interface before concluding that the group member on that interface is down and removing
the interface from the group. Possible values are 1 – 10. The default is 10.
To change these parameters, you must first enter the following CLI command at the global CLI level:
HP9300(config)# ip multicast-routing
Syntax: [no] ip multicast-routing
NOTE: You must enter the ip multicast-routing command before changing the global IP Multicast parameters.
Otherwise, the changes do not take effect and the software uses the default values.
Modifying IGMP Query Interval Period
The IGMP query interval period defines how often a routing switch will query an interface for group membership.
Possible values are 1 – 3,600 seconds and the default value is 60 seconds.
USING THE CLI
To modify the default value for the IGMP query interval, enter the following:
HP9300(config)# ip igmp query 120
Syntax: ip igmp query-interval <1-3600>
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