D-Link DGS-3630-52PC Manual - Page 862
Loopback Detection LBD Commands
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DGS-3630 Layer 3 Stackable Managed Switch CLI Reference Guide 67. Loopback Detection (LBD) Commands 67-1 loopback-detection (Global) This command is used to enable the loopback detection function globally. Use the no form of this command to disable the function globally. loopback-detection [mode {port-based | vlan-based}] no loopback-detection [mode] Parameters mode port-based vlan-based (Optional) Specifies the detection mode. Specifies that loop detection will work in the port-based mode. Specifies that loop detection will work in the VLAN-based mode. Default By default, this option is disabled. By default, the detection mode is port-based. Command Mode Global Configuration Mode. Command Default Level Level: 12. Usage Guideline Generally, port-based loop detection is used on ports that are connected to users, and VLAN-based detection is used in trunk or hybrid ports when the partner switch does not support the loop detection function. When port-based detection is enabled, the LBD enabled port will send untagged port-based LBD packets out from the port to discover the loop. If there is a loop occurrence in the path, then the packet being transmitted will loop back to the same port or to another port located on the same device. When an LBD enabled port detects a loop condition, packet transmitting and receiving is disabled on the port. When VLAN-based detection is enabled, the port will periodically send VLAN-based LBD packets for each VLAN that the port has membership in and is enabled for loop detection. If the port is a tagged member of the detecting VLAN, tagged LBD packets are sent. If the port is an untagged member of the detecting VLAN, untagged LBD packets are sent. If there is a loop occurrence on the VLAN path, then packet transmitting and receiving will be temporarily stopped in the looping VLAN at the port where the loop is detected. If an LBD disabled port receives an LBD packet and detects that the packet is sent out by the system itself, the sending port will be blocked if the packet is a port-based LBD packet, or the VLAN of the sending port will be blocked if the packet is a VLAN-based LBD packet. If the port is configured for VLAN-based detection and the port is an untagged member of multiple VLANs, then the port will send one untagged LBD packet for each VLAN with the VLAN number specified in the VLAN field of the packet. There are two ways to recover an error disabled port. The user can use the errdisable recovery cause loopbackdetect command to enable the auto-recovery of ports that were disabled by loopback detection. Alternatively, manually recover the port by entering the shutdown command followed by the no shutdown command for the port. The VLAN being blocked on a port can be automatically recovered, if the errdisable recovery cause loopbackdetect command is configured. Alternatively, manually recover the operation by entering the shutdown command followed by the no shutdown command for the port. 857
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