Foundry Networks FESX User Manual

Configuring Spanning Tree Protocol (STP) and IronSpan Features
December 2005 © Foundry Networks, Inc. 7 - 43
Then Switch 1, Switch 5, and Switch 6 send RST BPDUs that contain the TCN to Switch 3 and Switch 4 to
complete the TCN propagation (Figure 7.22).
Figure 7.22 Completing the TCN Propagation
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.
Port2 Port2
Port7 Port8
Port3
Port3
Port4Port4
Port3
Port2
Port3
2
Bridge priority = 200
Switch
4
Bridge priority = 400
Switch
Switch 3
Bridge priority = 300
1
Bridge priority = 1000
Switch
Port4
Port5
Port3
Port3
6
Bridge priority = 900
Switch
5
Bridge priority = 60
Switch
Port2
Port5 Port5
Port4
Indicates the active Layer 2 path
Indicates direction of TCN

Foundry Networks FESX Specifications

General

Brand	Foundry Networks
Model	FESX
Category	Switch
Language	English