Enabling or disabling the Spanning Tree Protocol (STP)
STP is enabled by default on devices running Layer 2 code. STP is disabled by default on devices running Layer 3 code.
You can enable or disable STP on the following levels:
- Globally - Affects all ports and port-based VLANs on the device.
- Port-based VLAN - Affects all ports within the specified port-based VLAN. When you enable or disable STP within a port-based VLAN, the setting overrides the global setting. Thus, you can enable STP for the ports within a port-based VLAN even when STP is globally disabled, or disable the ports within a port-based VLAN when STP is globally enabled.
- Individual port - Affects only the individual port. However, if you change the STP state of the primary port in a trunk group, the change affects all ports in the trunk group.
NOTE
The CLI converts the STP groups into topology groups when you save the configuration. For backward compatibility, you can still use the STP group commands. However, the CLI converts the commands into the topology group syntax. Likewise, the
show stp-group command displays STP topology groups.
Configuration modes for STP
The following configuration modes apply while configuring STP.
-
Spanning-tree single - This configuration can be enabled on systems running IEEE 802.1D. The single spanning tree controls all the 4000 VLANs. You can opt in and out of this single spanning tree using the spanning-tree command under the VLAN prompt.
- Spanning-tree single 802.1w - This configuration can be enabled on systems running IEEE 802.1w. The single rapid spanning tree controls all the 4000 VLANs. The VLAN can opt in and out of this single rapid spanning tree using the spanning-tree command under the VLAN prompt. If there is a “spanning-tree” configuration under the VLAN, that VLAN will be with that single 802.1w instance’s control, which implies that the VLAN traffic is subject to blocking or forwarding by that spanning tree instance.
- Per VLAN spanning tree - In this configuration mode you can turn on 802.1D or 802.1w (Rapid Spanning Tree) at the VLAN level individually.