Asked by: Yanelys Egghart
technology and computing computer networking

Is Rstp compatible with STP?

Last Updated: 22nd January, 2020

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In 2001, the IEEE introduced Rapid Spanning Tree Protocol (RSTP) as 802.1w. RSTP provides significantly faster recovery in response to network changes or failures, introducing new convergence behaviors and bridge port roles to do this. RSTP was designed to be backwards-compatible with standard STP.

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Just so, can STP and RSTP be mixed?

It is possible to mix PVST and MST (RSTP requires MST), but it needs some planning, and it can be fragile, as you have discovered. You would probably be better off using the same STP version across all your switches. You could change the STP on the Cisco switches to match the rest of the switches.

Subsequently, question is, how is RSTP faster than STP? RSTP converges faster because it uses a handshake mechanism based on point-to-point links instead of the timer-based process used by STP. For networks with virtual LANs (VLANs), you can use VLAN Spanning Tree Protocol (VSTP), which takes the paths of each VLAN into account when calculating routes.

Keeping this in view, what is the difference between RSTP and STP?

one difference is that Rapid Spanning Tree Protocol (RSTP IEEE 802.1W) assumes the three Spanning Tree Protocol (STP) ports states Listening, Blocking, and Disabled are same (these states do not forward Ethernet frames and they do not learn MAC addresses).

What are the RSTP port states?

RSTP defines three port states: discarding, learning, and forwarding and five port roles: root, designated, alternate, backup, and disabled. A RSTP capable switch determines what spanning tree will be computed by the algorithm, but the rules as written require knowledge of the entire network.

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How does Rstp work?

RSTP works by adding an alternative port and a backup port compared to STP. These ports are allowed to immediately enter the forwarding state rather than passively wait for the network to converge. The alternative port moves to the forwarding state if there is a failure on the designated port for the segment.

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Should spanning tree be enabled on all ports?

You configure the command “spanning-tree portfast” on all the ports connecting to end devices like workstations. It's important to only configure this command on ports that connect to end devices though. Ports connecting to other switches need to exchange spanning tree information.

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Is spanning tree still used?

Sadly, Spanning Tree will be around for decades to come while customers move to MLAG or even TRILL to reduce STP, instead replacing it completely with ECMP networking architectures.

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Why we use STP protocol?

Spanning Tree Protocol (STP) is a Layer 2 protocol that runs on bridges and switches. The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your network. Loops are deadly to a network.

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What is STP convergence time?

Spanning Tree Protocol (STP) convergence (Layer 2 convergence) happens when bridges and switches have transitioned to either the forwarding or blocking state. If a port has to go through all four states, convergence takes 50 seconds: 20 seconds in blocking, 15 seconds in listening, and 15 seconds in learning.

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What is protocol 802.1 D used for?

The standard Spanning Tree Protocol prevents loops when network switches or bridges are connected along multiple paths. The protocol uses the 802.1D algorithm. A bridge protocol data unit (BPDU) can be transmitted across a local area network to detect loops in topologies.

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What is PortFast?

Enabling the PortFast feature causes a switch or a trunk port to enter the STP forwarding-state immediately or upon a linkup event, thus bypassing the listening and learning states. The PortFast feature is enabled at a port level, and this port can either be a physical or a logical port.

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How does STP maintain a loop free network?

As the name implies, STP, spans all switches in a network or subnet. All switches generate and process data messages called Bridge Protocol Data Units (BPDUs). The STP algorithm is responsible for identifying active redundant links in the network and blocking one of these links, thus preventing possible network loops.

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What is STP and how does it work?

The Spanning Tree Protocol (STP) is responsible for identifying links in the network and shutting down the redundant ones, preventing possible network loops. In order to do so, all switches in the network exchange BPDU messages between them to agree upon the root bridge.

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What is a Bpdu packet?

Acronym for bridge protocol data unit. BPDUs are data messages that are exchanged across the switches within an extended LAN that uses a spanning tree protocol topology. BPDU packets contain information on ports, addresses, priorities and costs and ensure that the data ends up where it was intended to go.

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What is the default STP Hello Bpdu interval?

hello—The hello time is the time between each bridge protocol data unit (BPDU) that is sent on a port. This time is equal to 2 seconds (sec) by default, but you can tune the time to be between 1 and 10 sec. forward delay—The forward delay is the time that is spent in the listening and learning state.

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Which type does a port become when it receives the best BPDU on a bridge?

The port that receives the best BPDU on a bridge is the root port.

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What is alternate port?

An Alternate port provides a backup of your own Root port. If your Root port fails, the Alternate port is allowed to immediately transition into the Forwarding state and become the new Root port (in essence, the Alternate port is the one that receives the second best BPDU).

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How does STP elect root bridge?

Since the BID starts with the Bridge Priority field, essentially, the switch with the lowest Bridge Priority field becomes the Root Bridge. If there is a tie between two switches having the same priority value, then the switch with the lowest MAC address becomes the Root Bridge.