The IPv4 multicast routing management features supported by the system are: static multicast route, multicast routing policy, controlling the multicast forwarding range, controlling the capacity of a multicast forwarding table, testing multicast routes, multicast multi-topology and multicast splitting.
The static multicast route is an important factor of Reverse Path Forwarding (RPF) check. By configuring the static multicast route, users can specify the RPF interface and RPF neighbor for a specific source of packets on the current FW.
The static multicast route cannot be used to forward data. It only affects RPF check, and is also called static RPF route.
The static multicast route is valid only on the configured multicast FWs, and cannot be advertised or imported to other FWs.
If multiple unicast routes with the same cost exist when a multicast FW selects an upstream interface, users can use one of following methods to configure the FW to select the RPF route:
By default, the FW chooses the route with the largest next-hop address.
According to the longest match, the FW selects the route longest matching the address of the source of the packet.
Load splitting is configured among equal-cost routes. Performing load splitting of multicast traffic according to different policies can optimize network traffic transmission in the scenario where multiple multicast data flows exist.
There are five multicast load splitting policies: stable-preferred, balance-preferred, source address-based, group address-based, and source and group addresses-based. The five load splitting policies are mutually exclusive. In stable-preferred mode and balance-preferred mode, you can configure load splitting weights on the interfaces to achieve unbalanced multicast load splitting.
In a network, the multicast information to which each multicast group corresponds is transmitted in a certain range. Users can define the multicast forwarding range by using the following methods:
Configuring a multicast forwarding boundary on an interface to form a closed multicast forwarding area.
Setting the forwarding TTL threshold on an interface to limit the distance to which a packet is forwarded.
At the same time, users can prevent an interface of a multicast FW from receiving multicast packets. The multicast FW cannot exchange multicast protocol packets on the interface. The multicast forwarding range is thus limited.
When planning a specific network according to network services, the Internet Service Provider (ISP) can perform the following configurations:
Limiting the number of entries in the multicast forwarding table
Each FW maintains a forwarding entry for each received multicast packet. Too many multicast forwarding entries, however, use up the memory of a FW. Users can define the maximum number of entries in the multicast forwarding table of a FW. Limiting the number of entries according to the actual networking and service performance can avoid FW faults caused by excessive entries.
Limiting the number of downstream nodes of each forwarding entry
The FW replicates a multicast packet for each downstream node, and then sends it out. Each downstream node forms a branch of an MDT. The number of downstream nodes determines the maximum scale of the MDT and the multicast service range. Users can define the number of downstream nodes of a single forwarding entry. Limiting the number of downstream nodes according to the actual networking and service performance can reduce the processing pressure of a FW and control the multicast service range.
Multicast multi-topology enables multicast services to run in a specified topology, which isolates multicast services from unicast services.