Configuring LOOP-DETECT

Summary: Networking › Switching › Edge › Synapse

Overview of LOOP-DETECT

LOOP-DETECT is an Ethernet loop detection protocol, which is used to quickly detect loop faults on downlink interfaces. If a fault is found, LOOP-DETECT will notify the user to manually close or automatically close the relevant port according to the fault handling method configured by the user, so as to avoid affecting the normal data exchange. Enable control: Enable control is divided into global enable control and port enable control. When the global enable control is enabled and the loop detection is enabled on the port, the port supports the loop detection function. Loop action: When a loop fault is detected on the port, the user will be notified to manually handle the loop fault by default, and the automatic closing of the port can also be configured. When the port is automatically shut down, the port can recover from the fault by waiting for timeout, shutdown/no shutdown port, recovery command, or restarting the device. Specify vlan: By default, the port vlan attribute is ignored; if you need to detect whether a loop fault occurs in a specific vlan domain, you can configure the specified vlan on the port, and only detect Whether there is a loop data path in this vlan domain. The device supports loop fault alarm and loop fault recovery message traps to the snmp server, which is disabled by default.

Configuring

Enable LOOP-DETECT Globally

SWITCH(config)#loop-detect enable

SWITCH(config)#no loop-detect enable

Enable the LOOP-DETECT function globally. Disabled by default. Enable LOOP-DETECT On Interface

SWITCH(config-if)#loop-detect enable

SWITCH(config-if)#no loop-detect enable

Enabe the LOOP-DETECT Function Based on Ports. Disabled by default. Supports physical ports and AP ports, does not support AP members. Note： ✦ For a port in the block state, the protocol considers that there is no possibility of a loop. Even if the port is enabled for loop detection, the actual function cannot run normally. In an environment where stp and erps are enabled, a similar situation may exist. It is recommended to make the function mutually exclusive in the configuration.

SWITCH(config-if)#loop-detect action (alarm | error-down)

SWITCH(config-if)#no loop-detect action

Configure port loop action. Alarm: print alarm information. Error-down: print alarm information and shut down the port at the same time. The default action is alarm.

SWITCH(config-if)#loop-detect vlan VID

SWITCH(config-if)#no loop-detect vlan VID

SWITCH(config-if)#no loop-detect vlan

Detect whether a data path loop occurs in the specified vlan domain. VID supports single vlan mode and range mode, such as 10-12, separated by "," in the middle. A port can specify up to 8 vlans. By default, if no vlan is specified, the port vlan attribute will be ignored. If the port is in the block state, the data path is considered to be blocked.

SWITCH(config)#loop-detect interval SECONDS

SWITCH(config)#no loop-detect interval

Configure the interval for sending loop detection packets. SECONDS: range 5-300, default 5, unit second. Set Error-down Recovery Time

SWITCH(config)#errdisable timeout (interval SECONDS | enable | disable)

SWITCH(config)#no errdisable timeout interval

Configure errdisable recovery time. SECONDS: range 10-1000000, unit second. Enable: enable errdisable recovery. Disable: disable errdisable recovery. The default time is 300 seconds. The time is shared by all errdisable applications, configuring this parameter will affect other applications. Error-down Recovery Recovery interface from errdisable status. If errdisable timeout is disabled, this command will not work, please use shutdown and no shutdown commands to recovery interface.

SWITCH#errdisable recovery interface IFNAME

Recovery Interface to normal.

SWITCH(config)#loop-detect trap enable

SWITCH(config)#no loop-detect trap enable

Enable trap loop fault occurrence and loop fault recovery messages to the snmp server. Disabled by default. Definition of loop alarm trap node:

Mib files

DK-LDET-MIB.my oid 1, 3, 6, 1, 4, 1, 57430, 1, 6, 2,1

Ifindex

port index Definition of loop alarm recovery trap node: Node Data

Mib files

DK-LDET-MIB.my oid 1, 3, 6, 1, 4, 1, 57430, 1, 6, 2,2

Ifindex

port index

Examples

Case 1: Configure port gi0/1 to enable the loop detection function, and configure the action to err-down.

SWITCH#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

SWITCH(config)#loop-detect enable

SWITCH(config)#interface gigabitEthernet 0/1

SWITCH(config-if)# loop-detect enable

SWITCH(config-if)# loop-detect action error-down

When port gi0/1 detects a loop, it prompts the following information and shuts down the port. LOOPDETECT-4: %Loop error detected on interface GigabitEthernet 0/1.set interface err-down. Case 2: Configure port gi0/1 to perform loop detection in the vlan10 domain.

SWITCH#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

SWITCH(config)#vlan 10

SWITCH(config)#loop-detect enable

SWITCH(config)#interface gigabitEthernet 0/1

SWITCH(config-if)#switchport mode trunk

SWITCH(config-if)# loop-detect enable

SWITCH(config-if)# loop-detect vlan 10

The port gi0/1 sends loop detection messages with tag and vid is 10. If a loop is detected in the vlan10 domain, the log information is output. if peer interface not allow vlan10, no loop detected. LOOPDETECT-4: %Loop error detected on interface GigabitEthernet 0/1. Case 3: Configure port gi0/1 to enable loop detection, enable trap, and configure the snmp server 192.168.64.1.

SWITCH#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

SWITCH(config)#snmp-server group public v2c read all write all

SWITCH(config)#snmp-server community public

SWITCH(config)#snmp-server host 192.168.64.1 traps v2c community public

SWITCH(config)#loop-detect enable

SWITCH(config)# loop-detect trap enable

SWITCH(config)#interface gigabitEthernet 0/1

SWITCH(config-if)# loop-detect enable

When port gi0/1 detects a loop, the snmp server receives the loop alarm trap information.

Display Information

Display LOOP-DETECT Information

SWITCH#show loop-detect

Global configuration: Loop-detect State : Enabled Loop-detect Interval ：5 Loop-detect trap : Enabled Interface gigabitEthernet 0/1: Loop-detect State : Enabled Loop-detect Action : Alarm Loop-detect Action Last : Normal Loop-detect Action Last Time : — Loop-detect Action Count : 0 Loop-detect Vlans : 10, 20, 30-32 Analysis of the information：

Global Information

Loop-detect State Global enable status, Enabled or Disabled Loop-detect Interval Interval for sending loop detection packets, in seconds Loop-detect trap Whether to enable the alarm message trap to the server, Enabled or Disabled

Interface Information

Loop-detect State Interface enable status, Enabled or Disabled Loop-detect Action Action after loop detection, support alarm and error-down Loop-detect Action Last The last time a failure occurred: Normal: normal Alarm: output alarm Error-down: The port is down Loop-detect Action Last Time Time of last failure: No failures have occurred:– Happened, for example: 2022-01-10 22:45:23 Loop-detect Action Count

Count of failures

Loop-detect Vlans Loop packet specified vlan list