In
a High Availability (HA) active/passive configuration with firewalls
that use 10 gigabit SFP+ ports, when a failover occurs and the active
firewall changes to a passive state, the 10 gigabit Ethernet port
is taken down and then brought back up to refresh the port, but
does not enable transmit until the firewall becomes active again.
If you have monitoring software on the neighboring device, it will
see the port as flapping because it is going down and then up again.
This is different behavior than the action with other ports, such
as the 1 gigabit Ethernet port, which is disabled and still allows
transmit, so flapping is not detected by the neighboring device.