Everything about the err-disabled status

Everything about err-disabled status 1. the role of the err-disabled status: normally, if the switch is running normally, one of the ports is enabled. however, if the software of the switch (cisco ios/CatOS) detects some port errors, the port will be closed immediately. that is to say, when the operating system of the switch detects some errors on the switch port, the switch will automatically close the port. when the port is in the err-disabled status, no traffic is forwarded from the port and no inbound traffic is received. from the appearance of the switch, the corresponding LED status light on the port will also change from normal Green to dark yellow (or orange, I am blind, the official statement is amber, amber ). run the show interfaces command to check the port status. The port is in the err-disabled status. also, when the switch is disabled (err-disabled) due to an error, the following log information is typically seen: % SPANTREE-SP-2-BLOCK_BPDUGUARD: received BPDU on port GigabitEthernet2/1 with BPDU Guard enabled. disabling port. % PM-SP-4-ERR_DISABLE: bpduguard error detected on Gi2/1, putting Gi2/1 in err-disable state err-disabled: 1. an error occurred while notifying the administrator of the port status. 2. eliminate all ports or module function errors caused by a port error. II. cause of the err-disabled status: This feature was initially used to handle specific conflict situations, such as excessive collisison and late collision ). because of the CSMA/CD mechanism, frames will be discarded after 16 conflicts, and excessive collision will occur. late collision means that after the sender sends 64 bytes, normal and legal conflicts cannot occur. theoretically, normal network propagation will be completed before that, but if the line is too long, a conflict will occur after the first 64 bytes are completed, the most obvious difference between a later conflict and a conflict between the first 64 bytes is that the latter NIC will automatically re-transmit normal conflicting frames, but will not re-transmit the later conflicting frames. later conflicts occur at the time-out and remote end of the repeater. in general, such a conflict is identified as a frame verification sequence (FCS) error in the primary network segment. possible causes of this error include: 1. nonstandard use of cables, such as exceeding the maximum transmission distance or using an incorrect cable type. 2. the NIC is not working properly (physical damage or driver error ). 3. incorrect port duplex mode configuration, such as Duplex mismatch. the following are the reasons why the port is in the err-disabled status: 1. duplex mismatch. 2. incorrect port channel configuration. 3. violation of the BPDU Guard feature. 4. one-Way link detection (UDLD ). 5. later conflicts are detected. 6. link oscillation. 7. violates certain security policies. 8. the oscillation of the port aggregation protocol (PAgP. 9. layer 2 Tunneling Protocol (L2TP) Guard (L2TP Guard ). 10. DHCP listening speed limit. III. check whether the port is in the err-disabled status: You can use the show interfaces command to view the port status, such: NUAIKO # show interfaces gigabitethernet 2/1 status Port Name Status Vlan Duplex Speed Type Gi2/1 err-disabled 100 full 1000 1000 BaseSX when a Port of the switch is in the err-disabled status, the switch sends the log information for this operation to the Console port. you can also use show log to view system logs, such as: % SPANTREE-SP-2-BLOCK_BPDUGUARD: Received BPDU on port GigabitEthernet2/1 with BPDU Guard enabled. disabling port. % PM-SP-4-ERR_DISABLE: bpduguard error detected on Gi2/1, putting Gi2/1 in err-disable state % SPANTREE-2-CHNMISCFG: STP loop-channel 11/1-2 is disabled in vlan 1 if the errdisable recovery function is enabled, you can run the show errdisable recovery command to view the cause of err-disabled. For example: NUAIKO # show errdisable recovery ErrDisable Reason Timer Status