Dell PowerConnect FCS624S Configuration Guide - Page 297

Configuring STP related features 8 FIGURE 47 Completing the TCN propagation Switch 1 Bridge priority = 1000 Port2 Port3 Port7 Port8 Port2 Switch 2 Bridge priority = 200 Port5 Port3 Port4 Port2 Switch 5 Bridge priority = 60 Port3 Port2 Port3 Switch 3 Port4 Bridge priority = 300 Port3 Port4 Switch 4 Port5 Bridge priority = 400 Port4 Port3 Port5 Switch 6 Bridge priority = 900 Indicates the active Layer 2 path Indicates direction of TCN Compatibility of 802.1W with 802.1D 802.1W-enabled bridges are backward compatible with IEEE 802.1D bridges. This compatibility is managed on a per-port basis by the Port Migration state machine. However, intermixing the two types of bridges in the network topology is not advisable if you want to take advantage of the rapid convergence feature. Compatibility with 802.1D means that an 802.1W-enabled port can send BPDUs in the STP or 802.1D format when one of the following events occur: • The port receives a legacy BPDU. A legacy BPDU is an STP BPDU or a BPDU in an 802.1D format. The port that receives the legacy BPDU automatically configures itself to behave like a legacy port. It sends and receives legacy BPDUs only. • The entire bridge is configured to operate in an 802.1D mode when an administrator sets the bridge parameter to zero at the CLI, forcing all ports on the bridge to send legacy BPDUs only. Once a port operates in the 802.1D mode, 802.1D convergence times are used and rapid convergence is not realized. For example, in Figure 48, Switch 10 and Switch 30 receive legacy BPDUs from Switch 20. Ports on Switch 10 and Switch 30 begin sending BPDUs in STP format to allow them to operate transparently with Switch 20. PowerConnect B-Series FCX Configuration Guide 255 53-1002266-01