Rapid Spanning Tree Protocol (Rstp); Introduction - Nokia ESB26 User Manual

13. Rapid Spanning Tree Protocol
(RSTP)

Introduction

RSTP (Rapid Spanning Tree Protocol) performs the roles of the STP protocol considerably
faster by enabling rapid transitions of ports from Alternate state to Root state, and from
Backup state to Designated state. In certain cases, RSTP enables rapid transitions of ports to
Forwarding states.
RSTP is based on IEEE Std 802.1W and is part of Amendment 2: Rapid Reconfiguration to
IEEE Std 802.1D and IEEE Std 802.1t-2001.
RSTP assigns to each bridge port throughout the Bridged Local Area Network one of the
roles summarized in Table 13-1.
Table 13-1 RSTP Port Role Assignments
P o r t R o l e D e f i n i t i o n
Root Port Port connected to the root bridge/switch. State: forwarding and link enabled.
Designated Port Port connected to the designated switch - the switch closest to the root switch.
Frames are forwarded to the root through the designated switch.
Alternate Port Port that offers a path to the root bridge/switch alternate to the path provided by
the Root Port. The Alternate Port can replace the current root port if link failure
or a configuration change such as port priority change occurs. State: discarding
and link enabled.
Backup Port Backup for the path provided by a Designated Port in the direction of the leaves
of the Spanning Tree. Points away from the root. State: discarding and link
enabled.
Disabled Port Blocked port. State: discarding and link disabled.
MN700004 Rev 01
Figure 13-1 RSTP Port Roles
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