Note STP

STP

-definition

-effect

-Typ

1. 802.1d-STP: spanning Tree Protocol PVST/PVST+ (Cisco)

2. 802.1w-RSTP: rapid spanning Tree Protocol PV-RSTP (Cisco)

3. 802.1s-MSTP: multiple spanning Tree Protocol

-message

PVST:per-vlan STP, that is, running a STP (802.1d) inside each VLAN

The working process of STP:

1. Determine the role of the switch

Root switch: there is one and only one in the entire switching network

Non-root switch: the remaining switches are called non-root switches.

Note: each non-root switch will calculate the shortest, loop-free, layer 2 data forwarding path to the root switch, and eventually the path is in the "forwarding" state. Election principle: compare the BID (bridge ID) of each switch: priority + MAC address priority: default value is 32768; 2 bytes MAC address: use the MAC;6 bytes of the motherboard of the switch; comparison principle-first compare the priority, the smaller the better; secondly, compare the MAC address, the smaller the better; 2. Determine the role of the port root port: on each non-root switch, there is and only one. The port closest to the root switch; designated port: there is one and only one in each "network segment / segment"; the port closest to the root switch Non-designated port: all other ports, called "non-designated port" 3, determine the status of the port down-off (meaning that the current port does not have STP enabled) listening-listening, listening on all BPDU in the network in order to determine the role of the switch and port The port stays in this state for 15s; learning-learning, this stage is mainly to learn the source MAC address of the data frame received on the port, thus forming the MAC address table; the port stays in this state for 15s Forwarding-forwarding (final state), which implements the sending and receiving of packets blocking-blocking (final state), which cannot send and receive packets; can only receive BPDU.

BPDU type:

1. Configure BPDU

Used to create and maintain STP loop-free forwarding tree

2 、 TCN BPDU

Only when the STP loop-free forwarding path tree (topology) changes

Generate and send.

And it is: the switch that senses the change, generates TCN BPDU, and only

Send it to the root switch, and then forward it to all others

Non-root switch

STP timer:

Hello: the interval at which the switch periodically sends BPDU. The default is 2s.

Forward-delay: forwarding delay. Default time is 15s.

Max-age: maximum aging time. Default time is 20s.

STP parameter modification (Cisco):

1. Modify the STP priority of the switch (make sure there are primary and secondary root switches in the network)

Spanning-tree vlan x priority {value}, value is a multiple of 4096

2. Modify the STP mode of the switch (you must make sure that the STP mode of all switches on the network is the same) spanning-tree mode {pvst | rapid-pvst | mstp} 3, modify the port cost interface fas0/22 of the switch (the link refers to the trunk link) spanning-tree vlan 3 cost {value} 4, turn off the STP function no spanning-tree vlan x for a certain VLAN

STP parameter modification (Huawei):

1. Modify the STP priority of the switch:

[SW] stp priority {value}-> must be a multiple of 4096

2. Modify the STP mode of the switch

[SW] stp mode {stp | rstp | mstp}

3. Modify the STP cost of the switch port:

[SW] interface fas0/13

[sw-fas0/13] stp cost {value}

4. Turn off / enable STP on the switch:

[sw] stp disable-> close STP

[sw] stp enable-> enable STP. Default is enabled.

Verify the command:

Show spanning-tree vlan x-> you can view STP information about VLAN x on the switch

Show spanning-tree-> you can view STP information about all VLAN on the switch.

Show spanning-tree summary-> you can view the mode of the STP that the switch is running

Show version-> you can view the base mac of the switch

Display stp display stp brief

Note:

The STP function on the switch is on by default; it can be turned off manually

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Configuration of MSTP:

MST domain (region), which can contain multiple instances at the same time

MSTI (instance), that is, MST instance. A MSTI can be associated with multiple VLAN at the same time.

Configure MST region

[SW] stp region-configuration

[sw-mstp-region] name of region-name {string} / / configuration region

[sw-mstp-region] instance {id} vlan x y z m n / / configure the associated VLAN

[sw-mstp-region] active region-configuration

[sw-mstp-region] display this

Configure MSTI

[sw1] stp instance {id} priority {value}