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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 dynamicsynchronization 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.
• Layer 3 IP forwarding information - This includes the routing table, IP cache table, and ARP table, as
well as static and connected routes.
• If NSR is enabled, OSPFv2 and OSPFv3 information is copied to the standby.
As baseline synchronization is performed, the console of the active management module displays the
progress of the synchronization.
ACTIVE: Detected Stdby heart-beat
ACTIVE: Standby is ready for baseline synchronization.
ACTIVE: Baseline SYNC is completed. Protocol Sync is in progress.
ACTIVE: State synchronization is complete.
The first message indicates that the active management module has detected the standby management
module. The second message indicates that the standby module has been hot-inserted and is ready for
baseline synchronization. The third message is seen when baseline synchronization is completed, and
the fourth message is seen when protocol synchronization is completed.
The console of the standby management module also displays the progress of the synchronization.
STBY: Baseline SYNC is completed. Protocol Sync is in progress.
STBY: State synchronization is complete.
The first message indicates that baseline synchronization is completed, and the second message
indicates that protocol sychronization is completed.
When control protocols are synchronized and protocol synchronization timers expire, the standby
management module will be in
hot-standby mode, meaning the standby module is ready to take over as
the active management module. In the event of a switchover, the standby module will pick up where the
active module left off, without interrupting data traffic.
After baseline synchronization, any new events that occur on the active CPU will be dynamically
synchronized on the standby CPU. Examples of such events include:
• CLI/HTTP/SNMP configurations
• CPU receive packets
Real-time synchronization between management modules
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