Failure Scenarios In Nsr; Multicast Vpn - Cisco ASR 9000 Series Configuration Manual

Implementing Layer-3 Multicast Routing on Cisco IOS XR Software
Zero Packet Loss (ZPL) and Zero Topology Loss (ZTL). With Multicast NSR, there is less CPU churn and
no multicast session flaps during a failover event.
Multicast NSR is enabled by default, however, if any unsupported features like BNG or Snooping are
configured, Multicast performs Non-Stop Forwarding (NSF) functionality during failover events. When
Multicast NSR is enabled, multicast routing state is synchronized between the active and standby RSPs. Once
the synchronization occurs, each of the multicast processes signal the NSR readiness to the system. For the
multicast processes to support NSR, the processes must be hot standby compliant. That is, the processes on
active and standby RSPs both have to be in synchronization at all times. The active RSP receives packets
from the network and makes local decisions while the standby receives packet from the network and
synchronizes it with the active RSPs for all the local decisions. Once the state is determined, a check is
performed to verify if the states are synchronized. If the states are synchronized, a signal in the form
NSR_READY is conveyed to the NSR system.
With NSR, in the case of a failover event, routing changes are updated to the forwarding plane immediately.
With NSF, there is an NSF hold time delay before routing changes can be updated.
Non-Supported Features
The following features are unsupported on NG NSR:
• IGMP and MLD Snooping
• BNG

Failure Scenarios in NSR

If a switchover occurs before all multicast processes issue an NSR_READY signal, the proceedings revert
back to the existing NSF behavior. Also, on receiving the GO_ACTIVE signal from the multicast processes,
the following events occur in processes that have not signaled NSR_READY:
1 IGMP starts the NSF timer for one minute.
2 PIM starts the NSF timer for two minutes.
3 MSDP resets all peer sessions that are not synchronized.

Multicast VPN

Multicast VPN (MVPN) provides the ability to dynamically provide multicast support over MPLS networks.
MVPN introduces an additional set of protocols and procedures that help enable a provider to support multicast
traffic in a VPN.
Note PIM-Bidir is not supported on MVPN.
There are two ways MCAST VPN traffic can be transported over the core network:
• Rosen GRE (native): MVPN uses GRE with unique multicast distribution tree (MDT) forwarding to
enable scalability of native IP Multicast in the core network. MVPN introduces multicast routing
information to the VPN routing and forwarding table (VRF), creating a Multicast VRF. In Rosen GRE,
the MCAST customer packets (c-packets) are encapsulated into the provider MCAST packets (p-packets),
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 6.0.x
Multicast VPN
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