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FEFD State Changes
FEFD has two operational modes, Normal and Aggressive.
When you enable Normal mode on an interface and a far-end failure is detected, no intervention is
required to reset the interface to bring it back to an FEFD operational state. When you enable Aggressive
mode on an interface in the same state, manual intervention is required to reset the interface.
FEFD enabled systems (comprised of one or more interfaces) automatically switchs between four
different states: Idle, Unknown, Bi-directional, and Err-disabled.
1. An interface on which FEFD is not configured is in Normal mode by default.
2. After you enable FEFD on an interface, it transitions to the Unknown state and sends an FEFD packet
to the remote end of the link.
3. When the local interface receives the echoed packet from the remote end, the local interface
transitions to the Bi-directional state.
4. If the FEFD enabled system is configured to use FEFD in Normal mode and neighboring echoes are
not received after three intervals, (you can set each interval can be set between 3 and 300 seconds)
the state changes to unknown.
5. If the FEFD system has been set to Aggressive mode and neighboring echoes are not received after
three intervals, the state changes to Err-disabled. You must manually reset all interfaces in the Err-
disabled state using the fefd reset [interface] command in EXEC privilege mode (it can be
done globally or one interface at a time) before the FEFD enabled system can become operational
again.
Table 39. State Change When Configuring FEFD
Local
Event
Mode Local State Remote
State
Local
Admin
Status
Local
Protocol
Status
Remote
Admin
Status
Remote
Protocol
Status
Shutdown Normal Admin
Shutdown
Unknown Down Down Up Down
Shutdown Aggressive Admin
Shutdown
Err-
disabled
Up Down Up Down
FEFD
enable
Normal Bi-
directional
Bi-
directional
Up Up Up Up
FEFD
enable
Aggressive Bi-
directional
Bi-
directional
Up Up Up Up
FEFD +
FEFD
disable
Normal Locally
disabled
Unknown Up Down Up Down
FEFD +
FEFD
disable
Aggressive Locally
disabled
Err-
disabled
Up Down Up Down
Link Failure Normal Unknown Unknown Up Down Up Down
Link Failure Aggressive Err-
disabled
Err-
disabled
Up Down Up Down
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