380 BigIron RX Series Configuration Guide53-1001986-01Compatibility of RSTP with 802.1D13FIGURE 61 Completing the TCN propagationCompatibility of RSTP with 802.1DRSTP-enabled bridges are backward compatible with IEEE 802.1D bridges. This compatibility ismanaged on a per-port basis by the Port Migration state machine. However, intermixing the twotypes of bridges in the network topology is not advisable if you want to take advantage of the rapidconvergence feature.Compatibility with 802.1D means that an RSTP-enabled port can send BPDUs in the STP or 802.1Dformat 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 802.1Dformat. The port that receives the legacy BPDU automatically configures itself to behave like alegacy 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 rapidconvergence is not realized.Switch 1Bridge priority = 1000Switch 2Bridge priority = 200Switch 5Bridge priority = 60Switch 6Bridge priority = 900Switch 4Bridge priority = 400Switch 3Bridge priority = 300Port3Port3 Port3 Port3Port3Port2 Port2Port2Port4 Port4Port4Port4Port3Port2Port5Port5 Port5Port7 Port8Indicates the active Layer 2 pathIndicates direction of TCN
