3Com 2928 User Guide - Page 225

Item Bridge Diameter Description Any two stations in a switched network are interconnected through a specific path composed of a series of devices. The bridge diameter (or the network diameter) is the number of devices on the path composed of the most devices. After you set the network diameter, you cannot set the timers. Instead, the device automatically calculates the forward delay, hello time, and max age. Timers Forward Delay Hello Time Max Age z The configured network diameter is effective for CIST only, not for MSTIs. z The bridge diameter cannot be configured together with the timers. Set the delay for the root and designated ports to transit to the forwarding state. z The settings of hello time, Set the interval at which the device forward delay and max age sends hello packets to the surrounding must meet a certain formula. devices to ensure that the paths are Otherwise, the network fault-free. topology will not be stable. You are recommended to set the network diameter and then have the device Set the maximum length of time a configuration BPDU can be held by the device. automatically calculate the forward delay, hello time, and max age. z The bridge diameter cannot be configured together with the timers. Instance Instance ID Root Type Bridge Priority Set the role of the device in the MSTI or the bridge priority of the device, which is one of the factors deciding whether the device can be elected as the root bridge. Role of the device in the MSTI: z Not Set: Not set (you can set the bridge priority of the device when selecting this role) z Primary: Configure the device as the root bridge (you cannot set the bridge priority of the device when selecting this role) z Secondary: Configure the device as a secondary root bridge (you cannot set the bridge priority of the device when selecting this role). tc-protection Select whether to enable TC-BPDU guard. When receiving topology change (TC) BPDUs, the device flushes its forwarding address entries. If someone forges TC-BPDUs to attack the device, the device will receive a large number of TC-BPDUs within a short time and frequently flushes its forwarding address entries. This affects network stability. With the TC-BPDU guard function, you can prevent frequent flushing of forwarding address entries. tc-protection threshold You are recommended not to disable this function. Set the maximum number of immediate forwarding address entry flushes the device can perform within a certain period of time after receiving the first TC-BPDU. Return to MSTP configuration task list. 1-18