Addendum

image, after the kernel initialization is complete. Therefore, the forwarding plane match occurs at a later
time than the stage at which the match occurs when fast boot capability is not configured.
The following sections describe the working behavior of applications when fast boot functionality is
enabled and the various system conditions:
LACP and IPv4 Routing
The following events occur when the operator initiates a fastboot (prior to the CPU being reset) when
IPv4 routing is enabled on the system:
The system saves all dynamic ARP entries to a database on the flash drive.
A file is generated to indicate that the system is undergoing a fast boot, which is used after the system
comes up.
After the OS FTOS image has been loaded and activated, and the appropriate software components
come up, the following additional actions are performed:
• If a database of dynamic ARP entries is present on the flash drive, that information is read and the ARP
entries restored ; the entries are installed on the switch as soon as possible. At the same time, the
entries are changed to an initial (“aged out”) state so that they are refreshed (and flushed if not learnt
again). The database on the flash card is also deleted instantaneously.
• The system ensures that local routes known to BGP (configured through the network or
redistribute commands) are imported into BGP quickly and advertised to peers as quickly as
possible. In this process, any advertisement-interval configuration is not considered (only during the
initial period when the peer comes up).
If you do not configure BGP GR, you must configure the peering with BGP keepalive and hold timers to
be as high as possible (depending on your network deployment and the scaled parameters or sessions) to
enable the connection to be active until the ToR reinitializes the switch causing the links to adjacent
devices to go down. If the BGP sessions are disabled before the reinitialization of the switch occurs owing
to the timeout of the peer, traffic disruption occurs from that point onwards, although the ToR continues
to maintain valid routing information in hardware and is capable of forwarding traffic.
LACP and IPv6 Routing
The operation of the fast boot mechanism when the system is configured with IPv6 interfaces and has
IPv6 routes is similar to the processing that is done with IPv4 routing and LACP configured. The following
IPv6-related actions are performed during the reload phase:
• The system saves all of the dynamic ND cache entries to a database on the flash card. After the
system comes back online and the OS image is loaded and the corresponding software applications
on the system are also activated, the following processes specific to IPv6 are performed:
• If a database of dynamic ND entries is present on the flash, the same information is read and the ND
entries restored (to the IPv6 subsystem as well as the kernel); the entries are installed on the switch as
quickly as possible. At the same time, the entries are changed to an initial (“incomplete”) state so that
they are refreshed (and flushed if not learnt again). The database on the flash is also deleted
immediately.
• To ensure that the adjacent systems do not time out and purge their ND cache entries, the age-out
time or the reachable time for ND cache entries must be configured to be as high as necessary. We
recommend that you configure the reachable timer to be 90 seconds or longer.
Flex Hash and Optimized Boot-Up
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