Netgear XCM8806 - 8800 SERIES 6-SLOT CHASSIS SWITCH 사용자 설명서
Chapter 27. Multicast Routing and Switching
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NETGEAR 8800 User Manual
IP multicast routing requires the following functions:
•
A router that can forward IP multicast packets
•
A router-to-router multicast routing protocol (for example, Protocol Independent Multicast
(PIM)) to discover multicast routes
(PIM)) to discover multicast routes
•
A method for the IP host to communicate its multicast group membership to a router (for
example, Internet Group Management Protocol (IGMP))
Note:
You should configure IP unicast routing before you configure IP
multicast routing.
Multicast Routing Table and RPF Overview
Beginning with Release 12.1, all IP multicast routes are stored and maintained in the
software multicast route table. Routes are added to the multicast route table from the
following sources:
software multicast route table. Routes are added to the multicast route table from the
following sources:
•
Multicast static routes (configured manually by the network administrator)
•
Multicast dynamic routes (learned through protocols such as MBGP and MISIS)
The multicast route table is used for reverse path forwarding (RPF) checks, not for packet
routing. The switch uses RPF checks to avoid multicast forwarding loops. When a multicast
packet is received, the switch does an RPF lookup, which checks the routing tables to see if
the packet arrived on the interface on which the router would send a packet to the source.
The switch forwards only those packets that arrive on the interface specified for the source in
the routing tables.
routing. The switch uses RPF checks to avoid multicast forwarding loops. When a multicast
packet is received, the switch does an RPF lookup, which checks the routing tables to see if
the packet arrived on the interface on which the router would send a packet to the source.
The switch forwards only those packets that arrive on the interface specified for the source in
the routing tables.
The RPF lookup uses the multicast routing table first, and if no entry is found for the source
IP address, the RPF lookup uses the unicast routing table.
IP address, the RPF lookup uses the unicast routing table.
Note:
Because the multicast routing table is used only for RPF checks
(and not for routing), IP route compression and ECMP do not apply
to multicast routes in the multicast routing table.
to multicast routes in the multicast routing table.
Note:
The route metric is no longer used to select between multicast and
unicast routes. If the RPF lookup finds a route in the multicast table,
that route is used. The unicast routing table is used only when no
route is found in the multicast table.
that route is used. The unicast routing table is used only when no
route is found in the multicast table.
The advantage to having separate routing tables for unicast and multicast traffic is that the
two types of traffic can be separated, using different paths through the network.
two types of traffic can be separated, using different paths through the network.