Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 534

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, Bidirectional, 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 50. State Change When Configuring FEFD Local Event Mode Local State Remote State Local Admin Status Shutdown Normal Shutdown Aggressive FEFD enable FEFD enable FEFD + FEFD disable FEFD + FEFD disable Link Failure Link Failure Normal Aggressive Normal Aggressive Normal Aggressive Admin Shutdown Unknown Admin Shutdown Err-disabled Bi-directional Bi-directional Bi-directional Bi-directional Locally disabled Unknown Down Down Up Up Up Locally disabled Err-disabled Up Unknown Unknown Up Unknown Unknown Up Local Protocol Remote Admin Remote Status Status Protocol Status Down Up Down Down Up Down Up Up Up Up Down Up Up Up Down Down Up Down Down Up Down Up Down 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. 534 Layer 2