D-Link DGS-1520 Emulator - Page 1097

DGS-1520 Series Gigabit Ethernet Smart Managed Switch CLI Reference Guide Command Mode Interface Configuration Mode. Command Default Level Level: 12. Usage Guideline In the RSTP or STP-compatible mode, the administrative path cost is used by the single spanning-tree to accumulate the path cost to reach the Root. In the MSTP mode, the administrative path cost is used by the CIST regional root to accumulate the path cost to reach the CIST root. Example This example shows how to configure the port cost to 20000 on port 7. Switch#configure terminal Switch(config)#interface eth1/0/7 Switch(config-if)#spanning-tree cost 20000 Switch(config-if)# 99-9 spanning-tree guard root This command is used to enable the root guard mode. Use the no form of this command to revert to the default setting. spanning-tree guard root no spanning-tree guard root Parameters None. Default By default, this option is disabled. Command Mode Interface Configuration Mode. Command Default Level Level: 12. Usage Guideline BPDU guard prevents a port from becoming a root port. This feature is useful for the service provider to prevent external bridges to a core region of the network influencing the spanning tree active topology, possibly because those bridges are not under the full control of the administrator. When a port is guarded from becoming a root port, the port will only play the role as a designated port. If the port receives the configuration BPDU with a higher priority, the port will change to the alternate port, which is in the blocking state. The received superior factor will not participate in the STP computation. The port will listen for BPDUs on the link. If the port times out the received superior BPDU, it will change to the designated port role. When a port changes to the alternate port state, due to the root guard, a system message will be generated. This configuration will take effect for all the spanning-tree versions. 1093