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rapid+spanning+tree - Understanding Rapid Spanning Tree...

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Understanding Rapid Spanning Tree Protocol (802.1w) [Spanning Tree Protocol] - Cisco Systems Home | Log In | Register | Contacts & Feedback | Help | Site Map Select a Location / Language TECHNOLOGIES LAN SWITCHING PROTOCOL GROUPS SPANNING TREE PROTOCOL TECHNICAL DETAILS WHITE PAPERS Understanding Rapid Spanning Tree Protocol (802.1w) SPANNING TREE PROTOCOL Understanding Rapid Spanning Tree Protocol (802.1w) Downloads Understanding Rapid Spanning Tree Protocol (802.1w) Document ID: 24062 Contents Introduction Support of RSTP in Catalyst Switches New Port States and Port Roles Port States Port Roles New BPDU Format New BPDU Handling BPDU are Sent Every hello-time Faster Aging of Information Accepting Inferior BPDUs Rapid Transition to Forwarding State Edge Ports Link Type Convergence with 802.1d Convergence with 802.1w Proposal/Agreement Sequence UplinkFast New Topology Change Mechanisms Topology Change Detection Topology Change Propagation Compatibility with 802.1d Conclusion Related Information Introduction The current 802.1d Spanning Tree Protocol (STP) standard was designed at a time where recovering connectivity after an outage within a minute or so was considered adequate performance. With the advent of Layer 3 (L3) switching in LAN environments, bridging now competes with routed solutions where protocols such as Open Shortest Path First (OSPF) and Enhanced Interior Gateway Routing Protocol (EIGRP) are able to provide an alternate path in less time. Cisco enhanced the original 802.1d specification with features such as Uplink Fast , Backbone Fast , and Port Fast to speed up the convergence time of a bridged network. The drawback is that these mechanisms are proprietary and need additional configuration. Rapid Spanning Tree Protocol (RSTP; IEEE 802.1w) can be seen as an evolution of the 802.1d standard more than a revolution. The 802.1d terminology remains primarily the same, and most parameters have been left unchanged so users familiar with 802.1d can rapidly configure the new protocol comfortably. In most cases, RSTP performs better than Cisco's proprietary extensions without any additional configuration. 802.1w is also capable of reverting back to 802.1d in order to interoperate with legacy bridges (thus dropping the benefits it introduces) on a per-port basis. This document briefly explains the enhancements added by RSTP to the previous 802.1d standard. Support of RSTP in Catalyst Switches The table below shows the support of RSTP in Catalyst switches, and the minimum software required for that support. Catalyst Platform MST w/ RSTP RPVST+ (also known as PVRST+) Catalyst 2900 XL / 3500 XL Not available. Not available. Search: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml (1 of 10)3/4/2005 1:35:54 AM
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Understanding Rapid Spanning Tree Protocol (802.1w) [Spanning Tree Protocol] - Cisco Systems Catalyst 2940 Not available. Not available.
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