How to implement PIM multi-domain on the AR router


MSDP is designed to connect multiple PIM-SM domains. MSDP peer relationships are set up when multicast data needs to be transmitted between ASs.

Other related questions:
what are diffirence between PIM-SM and PIM-DM
PIM-DM: Small-scale LANs where multicast group members are distributed densely. Using the flood-prune mechanism, PIM-DM creates and maintains a unidirectional and loop-free SPT connecting a multicast source and group members. PIM-SM(ASM model): Large-scale network where multicast group members are distributed sparsely. An MDT is set up when receivers join a multicast group. PIM-SM needs to maintain an RP, set up an RPT, and register a multicast source. PIM-SM(SSM model): Scenarios where user hosts know the exact positions of multicast sources in advance and can specify the sources from which they want to receive data before they join multicast groups. PIM-SSM does not need to maintain an RP, set up an RPT, or register a multicast source.

Configure multi-carrier access on an AR router
The roadmap of configuring multi-carrier access on an AR router is as follows: 1. If users need to be forwarded to different carriers for Internet access, configure policy-based routing to implement access. 2. If users do not need to be forwarded to different carriers for Internet access, configure equivalent static routing to implement load sharing or backup routing to implement active/standby backup. 3. You can also configure policy-based routing to redirect a part of users to specified carrier lines and enable the remaining users to access the Internet through the default route.

How to implement port mapping on an AR router
Run the port-mapping command on an AR router to configure port mapping based on basic ACLs (number 2000 to 2999). Port mapping is implemented after packets match an ACL rule. To filter packets based on the ACLs, port mapping tries to match the destination IP addresses in the packets with the IP addresses defined in the basic ACL rules.
# Set the mapping port of the HTTP service to 10. If packets comply with the rules defined in the ACL 2000, the mapping relationship takes effect.
[Huawei] acl 2000
[Huawei-acl-basic-2000] rule permit
[Huawei-acl-basic-2000] quit
[Huawei] port-mapping http port 10 acl 2000

Can a PIM domain run PIM-DM and PIM-SM simultaneously
A PIM Domain cannot run PIM-DM and PIM-SM simultaneously. Since PIM Hello packets do not carry messages in PIM mode, a PIM switch cannot know the mode of the PIM protocol that its PIM neighbor runs. If the RPF interface and the RPF neighbor run PIM protocols of different modes, two neighboring devices cannot learn PIM routing information from each other. As a result, related multicast forwarding entries cannot be correctly created.

How to perform the RPF check for establishing an RPT in a PIM-SM domain
A receiver's DR first performs the RPF check: It searches for a unicast route to the RP. The outbound interface of the searched route acts as an upstream interface and the next hop of the searched route acts as an RPF neighbor. Then, the receiver's DR sends a Join message to the RPF neighbor. After receiving the Join message, the RPF neighbor performs the RPF check and forwards the Join message upstream at the same time. The Join message is sent upstream hop by hop until it reaches the RP. In the preceding process, if there is one device that has no route to the RP, the RPT cannot be established.

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