User's Manual

Table Of Contents
250
Users Manual of CS-6306R
directly connected to access switches. BackboneFast optimizes the maximum-age timer, which controls the
amount of time the switch stores protocol information received on an interface. When a switch receives an
inferior BPDU from the designated port of another switch, the BPDU is a signal that the other switch might
have lost its path to the root, and BackboneFast tries to find an alternate path to the root.
Backbone fast feature is only valid in SSTP/PVST mode.
Follow these steps to globally enable BackboneFast.:
Command Purpose
spanning-tree backbonefast Enables backbone fast feature.
no spanning-tree backbonefast Disables backbone fast feature.
20.1.2.7 Configuring Root Guard
Root guard enabled on an interface applies to all the VLANs to which the interface belongs. Do not enable the
root guard on interfaces to be used by the UplinkFast feature. With UplinkFast, the backup interfaces (in the
blocked state) replace the root port in the case of a failure. However, if root guard is also enabled, all the
backup interfaces used by the UplinkFast feature are placed in the root-inconsistent state (blocked) and are
prevented from reaching the forwarding state.
Root Guard feature acts differently somehow in SSTP/PVST and RSTP/MSTP. In SSTP/PVST mode, Root
port is always blocked by Root Guard. In RSTP/MSTP mode, Root port won’t be blocked until receiving higher
level BPDU. A port which formerly plays the Root role will not be blocked.
Follow these steps to enable root guard on an interface.:
Command Purpose
spanning-tree guard root Enables root guard feature on the interface.
no spanning-tree guard Disables root guard and loop guard features on the interface.
spanning-tree guard none Disables root guard and loop guard features on the interface.