Multiple techniques for providing failure protection in a network node that
includes primary and secondary control modules (CMs) are disclosed. One technique
involves synchronizing configuration state information between the CMs by executing
a configuration command within the primary CM and then executing the same configuration
command within the secondary CM only if executing the configuration command within
the primary CM does not cause the primary CM to fail. Another technique involves
gleaning table entries from hardware-based forwarding tables and using the gleaned
table entries to generate a software-based forwarding table in the secondary CM.
Another technique involves maintaining existing table entries in hardware-based
forwarding tables after a switchover, generating orphan table entry links at the
secondary CM to the existing table entries in the hardware-based forwarding tables,
and then using the links to manage the existing table entries until the secondary
CM can re-program the hardware-based forwarding tables.