PIM Over MCT Intermediate Router Functionality

MCT peers support intermediate router functionality by accepting PIM neighbors on specific interfaces, thus routing multicast traffic as fully functional PIM devices acting as upstream and downstream routers.

MCT peers support Protocol Independent Multicast (PIM) routing on Cluster Client Edge Port (CCEP) and Inter-Chassis Link (ICL) interfaces.

PIM states between MCT peers are synchronized by sending the control packets natively over the ICL. The nature of the MCT LAG requires this. Packets from the MCT client on the CCEPs are received by only one of the MCT peers. Therefore the control packets that are received natively on the CCEPs are sent over the ICL to synchronize the states. The join, prune, and assert packets are synchronized to maintain the Outgoing Interface (OIF) state for the CCEPs on both peers. For CCEP OIFs created by PIM joins, only one of the MCT peers forwards the traffic and the other peer drops the traffic.

These are the general rules followed for the control packet handling algorithm:

  • Control packets originated from MCT peers will be flooded on the MCT VLAN. Exceptions are assert packets and join packets triggered only for ICL OIFs.
  • Control packets received on any port of the MCT VLAN are flooded on the MCT VLAN.
  • Control packets received on the ICL are flooded in a controlled manner on the MCT VLAN based on remote CCEP status, that is, based on whether they are up or down.

Control and data packets received on an ICL port are processed by searching the source MAC address of the packet in the MAC table to determine the packet ingress port as follows:

  • If the source MAC address is learned on a CCEP, the packet ingress port will be a CCEP.
  • If the source MAC address is not learned on a CCEP, the packet ingress port will be an ICL port.

In the following figures, P1 and P2 are MCT peers and R1 is the MCT client. P1, P2, and R1 are configured with PIM on the MCT VE interface. MCT peers act as PIM intermediate routers with respect to R1.

In this section:

  1. MCT Peer as Intermediate Upstream Router
    P1 and P2 are the MCT peers and are acting as upstream routers for R1. R1 is the last-hop router (LHR).
  2. MCT Peer as Intermediate Downstream Router
    P1 and P2 are the MCT peers and are acting as downstream routers for R1. R1 is the intermediate router.
  3. Load Sharing of Multicast Traffic by MCT-Cluster on CCEP Links
    MCT peers load-share multicast traffic on both the local and the remote CCEP links when both are available.
  4. Fast Convergence of Multicast Traffic
    Multicast routing on MCT provides sub-second convergence of traffic in the event of CCEP or MCT peer failures and recoveries.
  5. First Hop and Last Hop Router Support on MCT Cluster Devices for MCT VLANs
    A First Hop Router (FHR), a multicast source that is directly connected to a router via cable or a switch, is supported on PIM cluster peers for MCT.
  6. RP Support on MCT Cluster Devices
    Rendezvous point (RP) is supported on MCT Cluster peer.
  7. Anycast RP Support for MCT Cluster Devices
    MCT cluster devices can be configured as anycast RP peers, thus providing redundancy to the RP.
  8. Requirements for Multicast MCT
  9. Limitations
    The following limitations apply for MCT peers to support intermediate router functionality. The limitations are due to load-sharing and fast convergence trade-offs.
  10. Configuring Multicast Routing over MCT for IPv4
Parent topic: Layer 3 Behavior with MCT