Extreme Networks ExtremeWare 7.3.0, Справочник по командам

Страница: 1479 / 2254

ExtremeWare Software 7.3.0 Command Reference Guide 1479
19
IP Multicast Commands
IP multicast routing is a function that allows a single IP host to send a packet to a group of IP hosts.
This group of hosts can include devices that reside on the local network, within a private network, or
outside of the local network.
IP multicast routing consists of the following functions:
• A router that can forward IP multicast packets
• A router-to-router multicast protocol [for example, Distance Vector Multicast Routing Protocol
(DVMRP) or Protocol Independent Multicast (PIM)]
• A method for the IP host to communicate its multicast group membership to a router [for example,
Internet Group Management Protocol (IGMP)]
NOTE
You must configure IP unicast routing before you configure IP multicast routing.
IGMP is a protocol used by an IP host to register its IP multicast group membership with a router.
Periodically, the router queries the multicast group to see if the group is still in use. If the group is still
active, a single IP host responds to the query, and group registration is maintained.
IGMP is enabled by default on the switch. However, the switch can be configured to disable the
generation of period IGMP query packets. IGMP query should be enabled when the switch is
configured to perform IP unicast or IP multicast routing.
Distance Vector Multicast Routing Protocol (DVMRP) is a distance-vector protocol that is used to
exchange routing and multicast information between routers. Like RIP, DVMRP periodically sends the
entire routing table to its neighbors.
DVMRP has a mechanism (flood and prune) that allows it to prune and graft multicast trees to reduce
the bandwidth consumed by IP multicast traffic.
Protocol Independent Multicast (PIM) is a multicast routing protocol with no inherent route exchange
mechanism. The switch supports dense mode and sparse mode operation. You can configure dense
mode or sparse mode on a per-interface basis. After they are enabled, some interfaces can run dense
mode, while others run sparse mode.