Deployment Guide

In the event of a far-end failure, the device stops receiving frames and, after the specified time interval, assumes that the
far-end is not available. The connecting line protocol is brought down so that upper layer protocols can detect the neighbor
unavailability faster.
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 switches 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 51. 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 Down 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 Unknown Unknown Up Down Up Down
Important Points to Remember
● FEFD enabled ports are subject to an 8 to 10 second delay during an RPM failover before becoming operational.
● You can enable FEFD globally or on a per-interface basis. Interface FEFD configurations override global FEFD configurations.
● Dell EMC Networking OS supports FEFD on physical Ethernet interfaces only, excluding the management interface.
● FEFD is not supported on Fibre Channel and copper Ethernet ports.
Configuring FEFD
You can configure FEFD for all interfaces from CONFIGURATION mode, or on individual interfaces from INTERFACE mode.
To enable FEFD globally on all interfaces, use the following command.
486
Layer 2