HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 2 - LAN Switching Co - Page 60
Basic concepts in STP, Root bridge, Root port, Designated bridge and designated port, Path cost
View all HP 6125G manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 60 highlights
Basic concepts in STP Root bridge A tree network must have a root bridge. The entire network contains only one root bridge. The other bridges in the network are called "leaf nodes." The root bridge is not permanent, but can change with changes of the network topology. Upon initialization of a network, each device generates and periodically sends configuration BPDUs with itself as the root bridge. After network convergence, only the root bridge generates and periodically sends configuration BPDUs, and the other devices forward the BPDUs. Root port On a non-root bridge, the port nearest to the root bridge is the root port. The root port communicates with the root bridge. Each non-root bridge has only one root port. The root bridge has no root port. Designated bridge and designated port Table 7 Description of designated bridges and designated ports Classification For a device For a LAN Designated bridge Designated port Device directly connected with the local device and responsible for forwarding BPDUs to the local device Port through which the designated bridge forwards BPDUs to this device Device responsible for forwarding BPDUs Port through which the designated bridge to this LAN segment forwards BPDUs to this LAN segment As shown in Figure 12, Device B and Device C are directly connected to a LAN. If Device A forwards BPDUs to Device B through port A1, the designated bridge for Device B is Device A, and the designated port of Device B is port A1 on Device A. If Device B forwards BPDUs to the LAN, the designated bridge for the LAN is Device B, and the designated port for the LAN is port B2 on Device B. Figure 12 Designated bridges and designated ports Path cost Path cost is a reference value used for link selection in STP. STP calculates path costs to select the most robust links and block redundant links that are less robust, to prune the network into a loop-free tree. 51