Reference Guide

PIM Sparse-Mode | 719
• The router holds on to the entries learned from the neighbor for the graceful restart interval. If it does
not receive a hello from the neighbor within this time, it purges all state associated with the neighbor.
• If the neighbor restarts and sends a hello with a new GenID before this interval expires, the router
sends a join message towards the neighbor for the relevant entries.
If a graceful-restart capable router restarts, the router preserves all multicast entries in hardware until it
receives and consolidates joins from its graceful-restart capable neighbors. The router is not taken off the
forwarding path during restart.
Enable PIM-SM graceful restart (non-stop forwarding capability) using the command
ip pim
graceful-restart nsf from CONFIGURATION mode. There are two options with this command:
•
restart-time is the time required by the Dell Force10 system to restart. The default value is 180
seconds.
•
stale-entry-time is the maximum amount of time that the Dell Force10 system preserves entries from a
restarting neighbor. The default value is 60 seconds.
In helper-only mode, the system preserves the PIM states of a neighboring router while the neighbor
gracefully restarts, but the Dell Force10 system allows itself to be taken off the forwarding path if it
restarts. Enable this mode using the command
ip pim graceful-restart helper-only. This mode takes
precedence over any graceful restart configuration.
First Packet Forwarding for Lossless Multicast
When the Dell Force10 system is the RP, packets arriving before an (S,G) entry is created are soft
forwarded using the (*,G) entry. This provides for zero multicast packet loss on FTOS with two
exceptions:
1. These packets can be soft (slow path) forwarded to receivers at a maximum rate of 70 packets/second.
Incoming packets beyond this rate are dropped.
2. When the system is both the source-DR and the RP, in some cases, packet loss, packet reordering, or
duplicate packets might occur.
To prevent these delivery errors you must statically map the potential incoming interfaces for the (*,G)
entries via the CLI. When you create this mapping, (*,G) entries are programmed in hardware. Packets are
then fast forwarded starting with the first packet, and the potential for these delivery errors is avoided.
Step Task Command Syntax Command Mode
1
Create a standard access-list that permits one or
more IGMP groups.
ip access-list standard name CONFIGURATION
FTOS(config-std-nacl)#show config
!
ip access-list standard map1
seq 5 permit 224.0.0.0/24