4.3 RSTP basic configuration
Principle overview
The 802.1w standard released by IEEE in 201 defines the RSTP
rapid spanning tree protocol, which has made detailed modifications and supplements to the original stp protocol.
Although stp solves the loop problem, it also has some shortcomings. There is no careful
distinction between port status and port role.
STP port status: disable blocking listening learning and forwarding. Convergence is slow. For users, there is no difference in the listening learning blocking state and no traffic is forwarded.
For the lack of rstpr, the following improvements have been made to
rstp and 2 new port roles have been added to rstp. 4 roles: Root port designated alternate port and backup port
alternate和backup:
The alternate port is a port blocked by learning configuration bpdu packets sent by other bridges. The alternate port provides another switchable path from the designated bridge to the root bridge, acting as a backup port for the root port
Backup port: The port blocked due to learning the configuration bpdu sent by itself. The backup port serves as the backup of the designated port and provides a backup port from the root bridge to the corresponding network segment.
rstp reduces the original 5 states to 3, which are divided according to whether the product forwards user traffic and learns the mac address:
no forwarding, no learning disable,
no forwarding learning,
forwarding learning, forwarding
Three fast convergence mechanisms:
proposla/agrrment mechanism: When a port is selected as a designated port, it will first enter the discarding state, and enter forwarding at the speed of the pa mechanism. It must be used on a full-duplex link
Root port fast switching mechanism: If the root port fails, the optimal alternate in the network will become the root port and enter the forwarding state. Because the network segment connected through this alternate port must have a designated port leading to the root bridge.
The introduction of edge ports: In rstp, if a designated port is located at the edge of the entire network, it is directly connected to the PC. This kind of port is called an edge port.
Do not receive the processing configuration bpdu does not participate in the rstp operation can be directly forwarded to the forwarding state from disable. No delay.
Once the edge port receives the configuration bpdu, it loses the attribute of the edge port and becomes a normal stp port. And re-calculate the spanning tree. This causes network shocks.
1. Experiment purpose and addressing
Understand the application scenario of rstp, basic configuration backup port
To simulate a corporate network, s3 and s4 are access layer switches. Responsible for user access.
s1 and s2 are aggregation switches. Four switches form a ring network. Run the rstp protocol.
s1 is the root s2 is the backup root
2. Experimental topology
2. Experimental content
1. Configure ip address for ping test
success
2. Configure the basic functions of rstp
将s1 s2 s3 s4将mstp改成rstp
stp mode rstp
在display stp查看根桥的位置
3. Root bridge is not root bridge
s1: stp root primary
s2: stp root secondary