Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 492
Far-End Failure Detection, FEFD State Changes
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Dell(conf-if-po-1)#switchport backup interface tengigabitethernet 1/2 Apr 9 00:16:29: %STKUNIT0-M:CP %IFMGR-5-L2BKUP_WARN: Do not run any Layer2 protocols on Po 1 and Te 1/2 Dell(conf-if-po-1)# Far-End Failure Detection Far-end failure detection (FEFD) is a protocol that senses remote data link errors in a network. FEFD responds by sending a unidirectional report that triggers an echoed response after a specified time interval. You can enable FEFD globally or locally on an interface basis. Disabling the global FEFD configuration does not disable the interface configuration. Figure 71. Configuring Far-End Failure Detection The report consists of several packets in SNAP format that are sent to the nearest known MAC address. 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. 492 Layer 2
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