Spanning tree protocol is a Layer 2 protocol that works on bridges and switches. The specification for spanning tree protocol is 802.1D and the main aim of this concept is when we have redundant paths in the network it avoids creating loops. So that the packets can flow easily without looping. As it was created in 1985 by that we can say it is a very old protocol designed by them and the advancement of this is a rapid spanning tree protocol created in 2001. Which is the higher version of spanning tree protocol? Rapid spanning tree protocol is an extension of the original spanning tree protocol.
The reason behind the expansion is to speed up the process and configurations remain the same. STP (802.1D) which is having five different port states called disabled, listening, learning, blocking, forwarding where disabled, blocking and listening merged into one and formed as discarding state in RSTP (802.1w). RSTP is having three different port states which are learning, forwarding, discarding.
Each state has a unique way of paths that learning port and forwarding port will be included in Active topology and grabs mac addresses whereas discarding port will not be included in active topology and it doesn’t grab mac addresses as well.
In Spanning tree protocol BPDU flag field has only two bits in use:
- Topology change.
- Topology change acknowledgment.
In Rapid spanning tree protocol, BPDU flag field all bits will be in usage, the roles involved in fields get added by the port role which has various options alternate port, backup port, root port, designated port and unknown.
RSTP makes it port in forwarding state to grab faster convergence on edge ports or point-to-point interfaces.
It has 2 link types:
- Point to point which is full-duplex.
- Shared which is half-duplex.
We can have a look on the convergence time of both the protocols, we have thirty seconds for the direct link and fifty seconds for the indirect link in spanning tree protocol and six seconds for default time and three seconds for hello interval time in rapid spanning tree protocol. While having a conversation for BPDU in STP only the Root port sends the Bridge port data unit and in rapid spanning tree protocol all bridges generate BPDU for every two seconds that delivers the mechanism of keepalive the system in the network.
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