Brocade FastIron Ethernet Switch Administration Guide - Manual (Page 118)

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
• Link events
• Interrupts
• Layer 2 and Layer 3 forwarding table updates
• Dynamic user authentication updates such as 802.1X or multi-device port authentication
• Routing protocols OSPFv2 and OSPFv3 updates if NSR is enabled.
Dynamic events are synchronized in such a way that if the active CPU fails before fully executing an
event, the standby CPU (newly active CPU) will execute the event after the failover. Also, if the active
CPU aborts the event, the standby CPU will abort the event as well.
Real-time synchronization between management modules
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