Configuration Guide User guide
FastIron Configuration Guide 101
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Hitless management on the FSX 800 and FSX 1600
• A hitless-reload must not have already been issued on the previous active management
module.
• POE firmware must not be in progress.
• The SXR running configuration must not be classified as too large (greater than 512KB).
• A TFTP session must not be in progress.
• An image sync session must not be in progress.
• The current active management card cannot have a memory utilization of greater than 90% of
available memory.
• A line card hotswap must not be in progress.
If any of these conditions are not met, an appropriate error message is printed to the console and
hitless-reload or switch-over will not succeed.
What happens during a Hitless switchover or failover
This section describes the internal events that enable a controlled or forced switchover (failover) to
take place in a hitless manner, as well as the events that occur during the switchover.
Separate data and control planes
The FSX 800 and FSX 1600 management modules have separate data and control planes. The
data plane forwards traffic between the switch fabric modules and all of the Interface modules in
the chassis. The control plane carries traffic that is destined for the CPU of the active management
module. Control plane traffic includes the following:
• Management traffic
• Control protocol traffic
• In some cases, the first packet of a data flow
During a controlled or forced switchover, the data plane is not affected. Traffic in the forwarding
plane will continue to run without interruption while the standby management module takes over
operation of the system. However, traffic in the control plane will be minimally impacted.
Real-time synchronization between management modules
Hitless management requires that the active and standby management modules are fully
synchronized at any given point in time. This is accomplished by baseline and dynamic
synchronization of the modules.
When a standby management module is inserted and becomes operational in the FSX 800 or FSX
1600 chassis, the standby module sends a baseline synchronization request to the active
management module. The request prompts the active management module to copy the current
state of its CPU to the standby CPU, including:
• Start-up and run-time configuration (CLI)
• Layer 2 protocols – Layer 2 protocols such as STP, RSTP, MRP, and VSRP run concurrently on
both the active and standby management modules.
• Hardware Abstraction Layer (HAL) – This includes the prefix-based routing table, next hop
information for outgoing interfaces, and tunnel information.