Must unicast routes be reachable when the multicast function is configured on an S series switch


Protocol independent multicast (PIM) uses routes in the unicast routing table. Therefore, PIM depends on a unicast routing protocol and can work only when unicast routes are reachable.

Other related questions:
Which unicast routing protocols and multicast protocols does GRE support
Generic routing encapsulation (GRE) supports the following unicast routing protocols: -Static routing protocols -OSPF -ISIS -RIP -BGP GRE supports protocol independent multicast (PIM), a multicast protocol.

What are differences between the multicast and unicast transmission modes for S series switches
Differences between the multicast and unicast transmission modes - In unicast transmission mode, a source sends an independent data packet to each host that requires data. In this mode, the amount of data transmitted on a network is proportional to the number of users who require the data. If a large number of users require the same data, the source must send many copies of the data to these users, consuming high bandwidth on the source and network. - Multicast is a point-to-multipoint (P2MP) data transmission mode. The source sends only one copy of data, and all the hosts that require the data can receive the same data. Other hosts on the network cannot receive the data. In multicast mode, data starts to be copied and distributed on the network node as far from the source as possible. Therefore, the amount of data and network resource consumption will not increase greatly when the number of receivers increases. Disadvantages of multicast transmission - Compared with the unicast mode, the multicast mode has no error correction mechanism, but some fault tolerance mechanisms can be adopted. - Although multicast transmission is supported by existing networks, features such as customer authentication and QoS are not well supported.

Differences between the three multicast-related routing tables on an S series switch
On an S series switch, the following tables are generally searched for MFIB entries: PIM routing table, multicast routing table, and multicast. - A PIM routing table contains entries generated by PIM at the protocol layer. You can view source and group information learned by PIM at the protocol layer in a PIM routing table. - A multicast routing table associates the protocol layer with the MFIB module. Entries at the protocol layer are stored in a multicast routing table before being delivered. Entries stored in the MFIB module must be the same as those stored in the multicast routing table. - A multicast forwarding table contains entries stored in the MFIB module. The MFIB module stores forwarding entries delivered from the protocol layer in the multicast forwarding table. The forwarding entries are then delivered to the multicast module of a switch. Normally, entries stored in the multicast forwarding table must be the same as those stored in the multicast routing table.

Do S series switches support static multicast routes
For S series switches, static multicast routes are supported only by S series modular switches, S3700EI, S3700HI, S5720S-SI, S5720SI, S5700EI, S5710EI, S5720EI, S5700HI, S5710HI, S5720HI, S6700EI, S6720EI and S6720S-EI. You can run the igmp static-group command to configure a static multicast group, and the ip rpf-route-static command to configure a static multicast route.

Why must unicast routes be reachable before multicast services are configured
Multicast devices do not maintain unicast routing information independently on the network. The devices must perform the RPF check on the received packets according to the unicast routing information on the network before creating PIM routing entries. If there is no unicast route to a specific destination, the RPF check fails.

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