Vlt Nodes As Rendezvous Points For Multicast Resiliency - Dell C9000 Series Networking Configuration Manual

VLT Nodes as Rendezvous Points for
Multicast Resiliency
You can configure virtual link trunking (VLT) peer nodes as rendezvous points (RPs) in a Protocol Independent
Multicast (PIM) domain.
PIM uses a VLT node as the RP to distribute multicast traffic to a multicast group. Messages to join the
multicast group (Join messages) and data are sent towards the RP, so that receivers can discover who the
senders are and begin receiving traffic destined for the multicast group.
To enable an explicit multicast routing table synchronization method for VLT nodes, you can configure VLT
nodes as RPs. Multicast routing needs to identify the incoming interface for each route. The PIM running on
both VLT peers enables both the peers to obtain traffic from the same incoming interface.
You can configure a VLT node to be an RP through the ip pim rp-address command in Global
Configuration mode. When you configure a VLT node as an RP, the (*, G) routes that are synchronized from
the VLT peers are ignored and not downloaded to the device. For the (S, G) routes that are synchronized from
the VLT peer, after the RP starts receiving multicast traffic via these routes, these (S, G) routes are considered
valid and are downloaded to the device. Only (S, G) routes are used to forward the multicast traffic from the
source to the receiver.
You can configure VLT nodes, which function as RP, as Multicast Source Discovery Protocol (MSDP) peers in
different domains. However, you cannot configure the VLT peers as MSDP peers in the same VLT domain. In
such instances, the VLT peer does not support the RP functionality.
If the same source or RP can be accessed over both a VLT and a non-VLT VLAN, configure better metrics for
the VLT VLANs. Otherwise, it is possible that one VLT node chooses a non-VLT VLAN (if the path through the
VLT VLAN was not available when the route was learned) and another VLT node selects a VLT VLAN. Such a
scenario can cause duplication of packets. ECMP is not supported when you configure VLT nodes as RPs.
Backup RP is not supported if the VLT peer that functions as the RP is statically configured. With static RP
configuration, if the RP reboots, it can handle new clients only after it comes back online. Until the RP returns
to the active state, the VLT peer forwards the packets for the already logged-in clients. To enable the VLT
peer node to retain the synchronized multicast routes or synchronized multicast outgoing interface (OIF)
maps after a peer node failure, use the timeout value that you configured through the multicast peer-
routing timeout value command. You can configure an optimal time for a VLT node to retain synced
multicast routes or synced multicast outgoing interface (OIF), after a VLT peer node failure, through the
multicast peer-routing-timeout command in VLT DOMAIN mode. Using the bootstrap router (BSR)
mechanism, both the VLT nodes in a VLT domain can be configured as the candidate RP for the same group
range. When an RP fails, the VLT peer automatically takes over the role of the RP. This phenomenon enables
resiliency to be achieved by the PIM BSR protocol.
Virtual Link Trunking (VLT) 1213