Users Guide

FEFD State Changes
FEFD has two operational modes: Normal and Aggressive.
When a far-end failure is detected on an FEFD-enabled interface:
• If the interface is in normal FEFD mode, no user intervention is required to reset the interface; it
automatically resets to an FEFD operational state.
• If the interface is in aggressive FEFD mode, manual intervention is required to reset the interface.
FEFD-enabled systems consist of one or more interfaces, which automatically switch between four 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, the state changes to unknown. You can set each interval from 3 to 255
seconds.
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 45. 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
Unknown 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 Up Up Down
Link Failure Normal Unknown Unknown Up Down Up Down
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