Huawei Quidway S3000 Series User manual

Operation Manual - STP
Quidway S3000 Series Ethernet Switches Table of Contents
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Table of Contents
Chapter 1 RSTP Configuration.....................................................................................................1-1
1.1 STP Overview....................................................................................................................1-1
1.1.1 Function of STP.......................................................................................................1-1
1.1.2 Implement STP........................................................................................................1-1
1.1.3 Implement RSTP on Ethernet Switch......................................................................1-7
1.2 Configure RSTP.................................................................................................................1-7
1.2.1 Enable/Disable RSTP on a Switch..........................................................................1-8
1.2.2 Enable/Disable RSTP on a Port.............................................................................. 1-8
1.2.3 Configure RSTP Operating Mode...........................................................................1-9
1.2.4 Set Priority of a Specified Bridge ............................................................................1-9
1.2.5 Specify the Switch as Primary or Secondary Root Switch.................................... 1-10
1.2.6 Set Forward Delay of a Specified Bridge..............................................................1-11
1.2.7 Set Hello Time of the Specified Bridge ................................................................. 1-12
1.2.8 Set Max Age of the Specified Bridge .................................................................... 1-12
1.2.9 Set Timeout Factor of the Bridge.......................................................................... 1-13
1.2.10 Set the Maximum Transmission Speed of the Specified Port............................. 1-13
1.2.11 Set Specified Port to be an EdgePort.................................................................1-14
1.2.12 Set Path Cost of the Specified Port .................................................................... 1-14
1.2.13 Set the Priority of a Specified Port......................................................................1-15
1.2.14 Configure a Specified Port to be Connected to Point-to-Point Link....................1-15
1.2.15 Set mCheck of the Specified Port.......................................................................1-16
1.2.16 Configure the Switch Security Function..............................................................1-17
1.3 Display and Debug RSTP................................................................................................1-18
1.4 RSTP Configuration Example..........................................................................................1-19
Chapter 2 MSTP Region-configuration .......................................................................................2-1
2.1 MSTP Overview.................................................................................................................2-1
2.1.1 MSTP Concepts...................................................................................................... 2-1
2.1.2 MSTP Principles...................................................................................................... 2-4
2.2 Configure MSTP ..............................................................................................................2-10
2.2.1 Configure the MST Region for a Switch................................................................2-11
2.2.2 Specify the Switch as Primary or Secondary Root Switch.................................... 2-13
2.2.3 Configure the MSTP Running Mode.....................................................................2-14
2.2.4 Configure the Bridge Priority for a Switch.............................................................2-15
2.2.5 Configure the Max Hops in an MST Region .........................................................2-15
2.2.6 Configure the Switching Network Diameter.......................................................... 2-16
2.2.7 Configure the Time Parameters of a Switch.........................................................2-16
2.2.8 Configure the Max Transmission Speed on a Port............................................... 2-18

Operation Manual - STP
Quidway S3000 Series Ethernet Switches Table of Contents
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2.2.9 Configure a Port as an Edge Port.........................................................................2-19
2.2.10 Configure the Path Cost of a Port.......................................................................2-20
2.2.11 Configure the Priority of a Port............................................................................2-21
2.2.12 Configure the Port (not) to Connect with the Point-to-Point Link........................ 2-22
2.2.13 Configure the mCheck Variable of a Port ...........................................................2-24
2.2.14 Configure the Switch Security Function..............................................................2-25
2.2.15 Enable MSTP on the Device...............................................................................2-26
2.2.16 Enable/Disable MSTP on a Port .........................................................................2-27
2.3 Display and Debug MSTP ............................................................................................... 2-28

Operation Manual - STP
Quidway S3000 Series Ethernet Switches Chapter 1 RSTP Configuration
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Chapter 1 RSTP Configuration
1.1 STP Overview
1.1.1 Function of STP
Spanning Tree Protocol ( STP ) is applied in loop network to block some undesirable
redundant paths with certain algorithms and prune the network into a loop-free tree,
thereby avoiding the proliferation and infinite cycling of the packet in the loop network.
1.1.2 Implement STP
The fundamental of STPis that the switches exchange a special kind of protocol packet
(which is called configuration Bridge Protocol Data Units, or BPDU, in IEEE 802.1D) to
decide the topology of the network. The configuration BPDU contains the information
enough to ensure the switches to compute the spanning tree.
The configuration BPDU mainly contains the following information:
1) The root ID consisting of root priority and MAC address
2) The cost of the shortest path to the root
3) Designated switch ID consisting of designated switch priority and MAC address
4) Designated port ID consisting of port priority and port number
5) The age of the configuration BPDU: MessageAge
6) The maximum age of the configuration BPDU: MaxAge
7) Configuration BPDU interval: HelloTime
8) Forward delay of the port: ForwardDelay.
What are the designated switch and designated port?

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Quidway S3000 Series Ethernet Switches Chapter 1 RSTP Configuration
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Switch A
Switch C
Switch B CP2
BP2
CP1
BP1
AP2AP1
LAN
Figure1-1 Designated switch and designated port
For a switch, the designated switch is a switch in charge of forwarding packets to the
local switch via a port called the designated port accordingly. For a LAN, the designated
switch is a switch that in charge of forwarding packets to the network segment via a port
called the designated port accordingly. As illustrated in the figure1-1, Switch Aforwards
data to Switch B via the port AP1. So to Switch B, the designated switch is Switch Aand
the designated port is AP1. Also in the figure above, Switch B and Switch C are
connected to the LAN and Switch B forwards packets to LAN. So the designated switch
of LAN is Switch B and the designated port is BP2.
Note:
AP1, AP2, BP1, BP2, CP1 and CP2 respectively delegate the ports of Switch A, Switch B and Switch C.
zThe specific calculation process of STP algorithm.
The following example illustrates the calculation process of STP.
The figure1-2 below illustrates the network.

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Quidway S3000 Series Ethernet Switches Chapter 1 RSTP Configuration
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Switch A
with priority 0
Switch C
with priority 2
Switch B
with priority 1 CP2
BP2 CP1
BP1
AP2
AP1
4
10
5
Figure1-2 Ethernet switch networking
To facilitate the descriptions, only the first four parts of the configuration BPDU are
described in the example. They are root ID (expressed as Ethernet switch priority), path
cost to the root, designated switch ID (expressed as Ethernet switch priority) and the
designated port ID (expressed as the port number). As illustrated in the figure above,
the priorities of SwitchA, B and C are 0, 1 and 2 and the path costs of their links are 5,
10 and 4 respectively.
9) Initial state
When initialized, each port of the switches will generate the configuration BPDU taking
itself as the root with a root path cost as 0, designated switch IDs as their own switch
IDs and the designated ports as their ports.
Switch A:
Configuration BPDU of AP1: {0, 0, 0, AP1}
Configuration BPDU of AP2: {0, 0, 0, AP2}
Switch B:
Configuration BPDU of BP1: {1, 0, 1, BP1}
Configuration BPDU of BP2: {1, 0, 1, BP2}
Switch C:
Configuration BPDU of CP2: {2, 0, 2, CP2}
Configuration BPDU of CP1: {2, 0, 2, CP1}
10) Select the optimum configuration BPDU
Every switch transmits its configuration BPDU to others. When a port receives a
configuration BPDU with a lower priority than that of its own, it will discard the message
and keep the local BPDU unchanged. When a higher-priority configuration BPDU is

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received, the local BPDU is updated. And the optimum configuration BPDU will be
elected through comparing the configuration BPDUs of all the ports.
The comparison rules are:
zThe configuration BPDU with a smaller root ID has a higher priority
zf the root IDs are the same, perform the comparison based on root path costs. The
cost comparison is as follows: the path cost to the root recorded in the
configuration BPDU plus the corresponding path cost of the local port is set as S,
the configuration BPDU with a smaller S has a higher priority.
zIf the costs of path to the root are also the same, compare in sequence the
designated switch ID, designated port ID and the ID of the port via which the
configuration BPDU was received.
In summary, we assume that the optimum BPDU can be selected through root ID
comparison in the example.
11) Specify the root port, block the redundancy link and update the configuration
BPDU of the designated port.
The port receiving the optimum configuration BPDU is designated to be the root port,
whose configuration BPDU remains the same. Any other port, whose configuration
BPDU has been updated in the step Select the optimum configuration BPDU, will be
blocked and will not forward any data, in addition, it will only receive but not transmit
BPDU and its BPDU remains the same. The port, whose BPDU has not been updated
in the step Select the optimum configuration BPDU will be the designated port. Its
configuration BPDU will be modified as follows: substituting the root ID with the root ID
in the configuration BPDU of the root port, the cost of path to root with the value made
by the root path cost plus the path cost corresponding to the root port, the designated
switch ID with the local switch ID and the designated port ID with the local port ID.
The comparison process of each switch is as follows.
Switch A:
AP1 receives the configuration BPDU from Switch B and finds out that the local
configuration BPDU priority is higher than that of the received one, so it discards the
received configuration BPDU. The configuration BPDU is processed on the AP2 in a
similar way. Thus Switch A finds itself the root and designated switch in the
configuration BPDU of every port; it regards itself as the root, retains the configuration
BPDU of each port and transmits configuration BPDU to others regularly thereafter. By
now, the configuration BPDUs of the two ports are as follows:
Configuration BPDU of AP1: {0, 0, 0, AP1}.
Configuration BPDU of AP2: {0, 0, 0, AP2}.
Switch B:

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BP1 receives the configuration BPDU from SwitchA and finds that the received BPDU
has a higher priority than the local one, so it updates its configuration BPDU.
BP2 receives the configuration BPDU from Switch C and finds that the local BPDU
priority is higher than that of the received one, so it discards the received BPDU.
By now the configuration BPDUs of each port are as follows: Configuration BPDU of
BP1: {0, 0, 0, AP1}, Configuration BPDU of BP2: {1, 0, 1, BP2}.
Switch B compares the configuration BPDUs of the ports and selects the BP1 BPDU as
the optimum one. Thus BP1 is elected as the root port and the configuration BPDUs of
Switch B ports are updated as follows.
The configuration BPDU ofthe root port BP1 retainsas {0, 0, 0, BP1}. BP2 updates root
ID with that in the optimum configuration BPDU, the path cost to root with 5, sets the
designated switch as the localswitch ID and the designated port ID as the local port ID.
Thus the configuration BPDU becomes {0, 5, 1, BP2}.
Then all the designated ports of Switch B transmit the configuration BPDUs regularly.
Switch C:
CP2 receives from the BP2 of Switch B the configuration BPDU {1, 0, 1, BP2} that has
not been updated and then the updating process is launched. {1, 0, 1, BP2}.
CP1 receives the configuration BPDU {0, 0, 0, AP2} from Switch A and Switch C
launches the updating. The configuration BPDU is updated as {0, 0, 0, AP2}.
By comparison, CP1 configuration BPDU is elected as the optimum one. The CP1 is
thus specified as the root port with no modifications made on its configuration BPDU.
However, CP2 will be blocked and its BPDU also remains same, but it will not receive
the data (excluding the STP packet) forwarded from Switch B until spanning tree
calculation is launched again by some new events. For example, the link from Switch B
to C is down or the port receives any better configuration BPDU.
CP2 will receive the updated configuration BPDU, {0, 5, 1, BP2}, from Switch B. Since
this configuration BPDU is better then the old one, the old BPDU will be updated to {0,
5, 1, BP2}.
Meanwhile, CP1 receives the configuration BPDU from Switch A but its configuration
BPDU will not be updated and retain {0, 0, 0, AP2}.
By comparison, the configuration BPDU of CP2 is elected as the optimum one, CP2 is
elected as the root port, whose BPDU will not change, while CP1 will be blocked and
retain its BPDU, but it will not receive the data forwarded from Switch A until spanning
tree calculation is triggered again by some changes. For example, the link from Switch
B to C as down.

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Quidway S3000 Series Ethernet Switches Chapter 1 RSTP Configuration
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Thus the spanning tree is stabilized. The tree with the root Switch A is illustrated in the
figure1-3 below.
Switch A
with priority 0
Switch C
with priority 2
Switch B
with priority 1 CP2
BP2
BP1
AP1
4
5
Figure1-3 The final stabilized spanning tree
To facilitate the descriptions, the description of the example is simplified. For example,
the root ID and the designated switch ID in actual calculation should comprise both
switch priority and switch MAC address. Designated port ID should comprise port
priority and port MAC address. In the updating process of a configuration BPDU, other
configuration BPDUs besides the first four items will make modifications according to
certain rules. The basic calculation process is described below:
zConfiguration BPDU forwarding mechanism in STP:
Upon the initiation of the network, all the switches regard themselves as the roots. The
designated ports send the configuration BPDUs of local ports at a regular interval of
HelloTime. If it is the root port that receives the configuration BPDU, the switch will
enable a timer to time the configuration BPDU as well as increase MessageAge carried
in the configuration BPDU by certain rules. If a path goes wrong, the root port on this
path will not receive configuration BPDUs any more and the old configuration BPDUs
will be discarded due to timeout. Hence, recalculation of the spanning tree will be
initiated to generate a new path to replace the failed one and thus restore the network
connectivity.
However, the new configuration BPDU as now recalculated will not be propagated
throughout the network right away, so the old root ports and designated ports that have
not detected the topology change will still forward the data through the old path. If the
new root port and designated port begin to forward data immediately after they are
elected, an occasional loop may still occur. In RSTP, a transitional state mechanism is
thus adopted to ensure the new configuration BPDU has been propagated throughout
the network before the root port and designated port begin to send data again. That is,
the root port and designated port should undergo a transitional state for a period of
Forward Delay before they enter the forwarding state.

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1.1.3 Implement RSTP on Ethernet Switch
The Ethernet Switch implements the Rapid Spanning Tree Protocol (RSTP), i.e., the
enhancement of STP. The Forward Delay for the root ports and designated ports to
enter forwarding state is greatly reduced in certain conditions, thereby shortening the
time period for stabilizing the network topology.
To achieve the rapid transition of the root port state, the following requirement should
be met: The old root port on this switch has stopped data forwarding and the
designated port in the upstream has begun forwarding data.
The conditions for rapid state transition of the designated port are:
zThe port is an Edge port that does not connect with any switch directly or indirectly.
If the designated port is an edge port, it can switch to forwarding state directly
without immediately forwarding data.
zThe port is connected with the point-to-point link, that is, it is the master port in
aggregation ports or full duplex port. It is feasible to configure a point-to-point
connection. However, errors may occur and therefore this configuration is not
recommended. If the designated port is connected with the point-to-point link, it
can enter the forwarding state right after handshaking with the downstream switch
and receiving the response.
The switch that uses RSTPis compatible with the one using STP. Both protocol packets
can be identified by the switch running RSTP and used in spanning tree calculation.
Note:
RSTP is the protocol of single spanning tree. A switching network only has one spanning tree. To
guarantee the normal communication inside a VLAN, the devices of a VLAN shall have routes to one
anotherontheSpanningTree,otherwise,thecommunicationinsidetheVLANwillbeaffectedifsomelinks
inside a VLAN are blocked.
For some VLAN that cannot be arranged along the spanning tree paths for some special requirements,
you have to disable RSTP on the switch port corresponding to the VLAN.
1.2 Configure RSTP
RSTP configuration includes:
zEnable/Disable RSTP on the switch
zEnable/Disable RSTP on the port
zConfigure RSTP Operating Mode
zSet priority of a specified bridge

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zSet Forward Delay of a specified bridge
zSet Hello Time of the specified bridge
zSet Max Age of the specified bridge
zSet the maximum transmission speed of the specified port
zSet specified port as the EdgePort
zSet path cost of the specified port
zSet the priority of a specified port
zConfigure a specified port to be connected to a point-to-point link
zSet mCheck of the specified port
Among the above-mentioned tasks, only the steps of enabling STP on the switch and
enabling STPon the port are required. For other tasks, if you do not configure them, the
system will use the default settings.
Before enabling spanning tree, relative parameters of Ethernet port or the device can
be configured.After disabling the spanning tree, these configuration parameters will be
reserved and becoming functional after enabling the spanning tree again.
1.2.1 Enable/Disable RSTP on a Switch
You can use the following command to enable RSTP on the switch.
Perform the following configurations in system view.
Table1-1 Enable/Disable RSTP on a device
Operation Command
Enable/Disable RSTP on a device stp {enable |disable }
Restore RSTP to the default value undo stp
Only after the RSTP is enabled on the switch can other configurations take effect.
Note that some network resource will be occupied after RSTP is enabled.
By default, RSTP is disabled.
1.2.2 Enable/Disable RSTP on a Port
You can use the following command to enable/disable the RSTPon the designated port.
To flexibly control the RSTPoperations, after RSTP is enabled on the Ethernet ports of
the switch, it can be disabled again to forbid the ports to participate in the spanning tree
calculation.
Perform the following configurations in Ethernet port view.

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Quidway S3000 Series Ethernet Switches Chapter 1 RSTP Configuration
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Table1-2 Enable/Disable RSTP on a port
Operation Command
Enable RSTP on a specified port stp enable
Disable RSTP on a specified port stp disable
Note that the redundancy route may be generated after RSTP is disabled on the
Ethernet port.
By default, RSTP on all the ports will be enabled after it is enabled on the switch.
1.2.3 Configure RSTP Operating Mode
RSTP is executable in RSTP mode or STP-compatible mode. RSTP mode is applied
when all the network devices provided for executing RSTP, while the STP-compatible
mode is applied when both STP and RSTP are executable on the network.
You can use the following command to set the RSTP operating mode.
Perform the following configurations in system view.
Table1-3 Set RSTP operating mode
Operation Command
Configure to run RSTP in STP-compatible/RSTPmode stp mode {stp |rstp }
Restore the default RSTP mode undo stp mode
Normally, if there is a bridge provided to execute STP in the switching network, the port
(in the switch running RSTP), which connects to another port (in the switch for
executing STP), can automatically switch to STP compatible mode from RSTP mode.
By default, RSTP runs in RSTP mode.
1.2.4 Set Priority of a Specified Bridge
Whether a bridge can be selected as the “root” of the spanning tree depends on its
priority. By assigning a lower priority, a bridge can be artificially specified as the root of
the spanning tree.
You can use the following command to configure the priority of a specified bridge.
Perform the following configurations in system view.

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Table1-4 Set priority of a specified bridge
Operation Command
Set priority of a specified bridge stp priority bridge-priority
Restore the default priority of specified bridge undo stp priority
Note that if the priorities of all the bridges in the switching network are the same, the
bridge with the smallest MAC address will be selected as the “root”. When RSTP is
enabled, an assignment of a priority to the bridge will lead to recalculation of the
spanning tree.
By default, the priority of the bridge is 32768.
1.2.5 Specify the Switch as Primary or Secondary Root Switch
RSTP can determine the spanning tree root through calculation. You can also specify
the current switch as the root using this command.
You can use the following commands to specify the current switch as the primary or
secondary root of the spanning tree.
Perform the following configuration in system view.
Table1-5 Specify the switch as primary or secondary root switch
Operation Command
Specify the current switch as the primary root switch of the spanning tree. stp root primary
Specify the current switch as the secondary root switch of the spanning tree. stp root secondary
Disqualify the current switch as the primary or secondary root. undo stp root
After a switch is configured as primary root switch or secondary root switch, user can’t
modify the bridge priority of the switch.
A switch can either be a primary or secondary root bridge, but not both of them.
If the primary root of a spanning tree instance is down or powered off, the secondary
root will take its place, unless you configure a new primary root. Of two or more
configured secondary root switches, RSTP selects the one with the smallest MAC
address to take the place of the failed primary root.

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Note:
To configure a switch as the root of the spanning tree instance, you can specify its priority as 0 or simply
set it as the root, using the command.
Itisnotnecessarytospecifytwoor moreroots foranSTI.Inother words,please donotspecifythe rootfor
an STI on two or more switches.
YoucanconfiguremorethanonesecondaryrootforaspanningtreethroughspecifyingthesecondarySTI
root on two or more switches.
Generally, you are recommended to designate one primary root and more than one secondary roots for a
spanning tree.
By default, a switch is neither the primary root nor the secondary root of the spanning
tree.
1.2.6 Set Forward Delay of a Specified Bridge
Link failure will cause recalculation of the spanning tree and change its structure.
However, the newly calculated configuration BPDU cannot be propagated throughout
the network immediately. If the newly selected root port and designated port begin to
forward data frame right away, occasional loop can be caused. Accordingly, the
protocol adopts a state transition mechanism, that is, the root port and the designated
port must undergo a transition state for a period of Forward Delay before they transition
to the forwarding state and resume data frame forwarding. This delay ensures that the
new configuration BPDU has been propagated throughout the network before the data
frame forwarding is resumed.
You can use the following command to set the Forward Delay for a specified bridge.
Perform the following configurations in system view.
Table1-6 Set forward delay of a specified bridge
Operation Command
Set Forward Delay of a specified bridge stp timer forward-delay centiseconds
Restore the default Forward Delay of specified bridge undo stp timer forward-delay
Forward Delay of the bridge is related to the diameter of the switching network. As a
rule , the larger the network diameter , the longer the Forward Delay. Note that if the
Forward Delay is configured too short, occasional path redundancy may occur. If the
Forward Delay is configured too long, the restoring of network connection may take a
long time. It is recommended to use the default setting.
By default, the bridge Forward Delay is 15 seconds.

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1.2.7 Set Hello Time of the Specified Bridge
Abridge transmits hello packet regularly to the adjacent bridges to check if there is link
failure.
You can use the following command to set the Hello Time of a specified bridge.
Perform the following configurations in system view.
Table1-7 Set Hello Time of the specified bridge
Operation Command
Set Hello Time of the specified bridge stp timer hello centiseconds
Restore the default Hello Time of the specified bridge undo stp timer hello
Appropriate Hello Time can ensure that the bridge can detect the link failure in the
network in time without occupying too many network resources. If the Hello Time is too
long it will result in the spanning tree recalculation because the bridge mistakes due to
the frame dropping of the link for link failure. If the Hello Time is too short, it will result
in frequently sending of configuration BPDUs by the bridge and thus unduly increasing
the switch load and wastes of network resource.
By default, the Hello Time of the bridge is 2 seconds.
1.2.8 Set Max Age of the Specified Bridge
Max Age is a parameter to judge whether the configuration BPDU is “timeout”. Users
can configure it according to the actual network situation.
You can use the following command to set MaxAge of a specified bridge.
Perform the following configurations in system view.
Table1-8 Set Max Age of the specified bridge
Operation Command
Set MaxAge of the specified bridge stp timer max-age centiseconds
Restore the default MaxAge of the specified bridge undo stp timer max-age
If the Max Age is too short, it will result in frequent calculation of spanning tree or
misjudge the network congestion as a link fault. On the other hand, too long Max Age
may make the bridge unable to find link failure in time and weaken the network
auto-sensing ability. It is recommended to use the default setting.
By default, the bridge Max Age is 20 seconds.

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1.2.9 Set Timeout Factor of the Bridge
Abridge transmits hello packet regularly to the adjacent bridges to check if there is link
failure. Generally, if the switch doesn’t receive the RSTP packets from the upstream
switch for 3 times of hello time, the switch will decide the upstream switch is dead and
will recalculate the topology of the network. Then in steady network, the recalculation
may be caused when the upstream is busy. In this case, user can redefine the timeout
interval to a longer time by define the multiple of hello time.
You can use the following command to set the multiple value of hello time of a specified
bridge.
Perform the following configurations in system view.
Table1-9 Set Timeout Factor of the Bridge
Operation Command
Set the multiple value of hello time of a specified bridge stp timeout-factor number
Restore the default multiple value of hello time undo stp timeout-factor
It is recommended to set 5, 6 or 7 as the value of multiple in the steady network.
By default, the multiple value of hello time of the bridge is 3.
1.2.10 Set the Maximum Transmission Speed of the Specified Port
The maximum transmission speed of Ethernet port is related to its physical state and
network structure. Users can configure it according to the actual network situation.
You can use the following command to set the maximum transmission speed of the
specified port.
Perform the following configurations in Ethernet port view.
Table1-10 Set the maximum transmission speed of the specified port
Operation Command
Set the maximum transmission speed of the specified port stp transit-limit packetnum
Restore the default maximum transmission speed of the
specified port undo stp transit-limit
If the max transmission speed on a port is too high, there will be too many packets
being transmitted per unit time, which occupies excessive network resources. It is
recommended to use the default setting.

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By default, the maximum transmission speed is 3 (a counter value without unit) on all
the Ethernet ports of the bridge.
1.2.11 Set Specified Port to be an EdgePort
EdgePort is not connected to any switch directly or indirectly via the connected
network.
You can use the following command to set a specified port as an EdgePort.
Perform the following configurations in Ethernet port view.
Table1-11 Set specified port as the EdgePort
Operation Command
Set a specified port as an EdgePort or a non-EdgePort stp edged-port {enable | disable }
Set the specified port as the non-EdgePort, as defaulted undo stp edged-port
In the process of recalculating the spanning tree, the EdgePort can transfer to the
forwarding state directly and reduce unnecessary transition time. If the current
Ethernet port is not connected with any Ethernet port of other bridges, this port should
be set as an EdgePort. If a specified port connected to a port of any other bridge is
configured as an edge port, RSTP will automatically detect and reconfigure it as a
non-EdgePort.
After the network topology changed, if a configured non-EdgePort changes to an
EdgePort and is not connected to any other port, it is recommended to configure it as
an EdgePort manually because RSTP cannot configure a non-EdgePort as an
EdgePort automatically.
Configure the port directly connected to the terminal as an EdgePort, so that the port
can transfer immediately to the forwarding state.
By default, all the Ethernet ports are configured as non-EdgePort.
1.2.12 Set Path Cost of the Specified Port
The path cost of Ethernet port is related to the speed of a link connected to the port.
You can use the following command to set the Path Cost of a specified port.
Perform the following configurations in Ethernet port view.

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Table1-12 Set path cost of the specified port
Operation Command
Set path cost of the specified port stp cost cost
Restore the default path cost of the specified port undo stp cost
The path cost of Ethernet port is related to its link speed. The higher the link speed is,
the lower the path cost should be configured. RSTP can automatically detect the link
speed on the current Ethernet port and convert it to the corresponding path cost. Note
that configuring path cost of an Ethernet port will cause the recalculation of the
spanning tree. It is recommended to use the default value and let RSTP calculate the
path cost on the current Ethernet port.
By default, the bridge gets the path cost of a port according to the link speed directly.
1.2.13 Set the Priority of a Specified Port
The port priority is an important basis to decide if the port can be a root port. In the
calculation of the spanning tree, the port with the highest priority will be selected as the
root assuming all other conditions are the same.
You can use the following command to set the priority of a specified port.
Perform the following configurations in Ethernet port view.
Table1-13 Set the priority of a specified port
Operation Command
Set the priority of a specified port stp port priority port-priority
Restore the default priority of the specified port undo stp port priority
By setting the priority of an Ethernet port, you can put a specified Ethernet port into the
final spanning tree. Generally, the lower the value is set, the higher priority the port has
and the more likely it is for this Ethernet port to be included in the spanning tree. If all
the Ethernet ports of the bridge adopt the same priority parameter value, then the
priority of these ports depends on the Ethernet port index number. Note that changing
the priority of Ethernet port will cause recalculation of the spanning tree. You can set
the port priority at the time when setting up the networking requirements.
By default, priorities of all the Ethernet ports are 128.
1.2.14 Configure a Specified Port to be Connected to Point-to-Point Link
Generally, a point-to-point link connects the switches.

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You can use the following command to configure a specified port to be connected to a
point-to-point link.
Perform the following configurations in Ethernet port view.
Table1-14 Configure a specified port to be connected to a point-to-point link
Operation Command
Configure a specified port to be connected to a point-to-point link stp point-to-point force-true
Configure a specified port not to be connected to a point-to-point
link stp point-to-point force-false
ConfigureRSTPto automaticallydetect ifthe portis connectedto a
point-to-point link. stp point-to-point auto
Configure the port to be automatically detected if it is connected to
a point-to-point link, as defaulted. undo stp point-to-point
The two ports connected via the Point-to-Point link can enter the forwarding state
rapidly by transmitting synchronous packets, so that the unnecessary forwarding delay
can be reduced. If this parameter is configured to be auto mode, RSTP can
automatically detect if the current Ethernet port is connected to a Point-to-Point link.
Note that, for an aggregated port, only the master port can be configured to connect
with the point-to-point link. After auto-negotiation, the port working in full duplex can
also be configured to connect with such link.
You can manually configure the active Ethernet port to connect with the Point-to-Point
link. However, if the link is not a point-to-point link, the command may cause a system
problem, and therefore it is recommended to set it as auto mode.
By default, this parameter is configured to auto, namely in auto mode.
1.2.15 Set mCheck of the Specified Port
Suppose there are some switches running STP and some other switches running
RSTP on a switching network. RSTP is STP-compatible. In a relatively stable network,
though the bridge running STPhas been removed, the port of the switch running RSTP
is still working in STP-compatible mode. You can use the following command to
manually command the port to work in RSTP mode. This command can only be issued
if the bridge runs RSTP in RSTP mode and has no effect in the STP-compatible mode.
You can use the following command to configure mCheck of a specified port.
Perform the following configurations in Ethernet port view.

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Table1-15 Set mCheck of the specified port
Operation Command
Set mCheck of the specified port stp mcheck
This command can be used when the bridge runs RSTP in RSTP mode, but it cannot
be used when the bridge runs RSTP in STP-compatible mode.
1.2.16 Configure the Switch Security Function
An RSTP switch provides BPDU protection and Root protection functions.
For an access device, the access port is generally directly connected to the user
terminal (e.g., PC) or a file server, and the access port is set to edge port to implement
fast transition. When such port receives BPDU packet, the system will automatically set
it as a non-edge port and recalculate the spanning tree, which causes the network
topology flapping. In normal case, these ports will not receive STP BPDU. If someone
forges BPDU to attack the switch, the network will flap. BPDU protection function is
used against such network attack.
In case of configuration error or malicious attack, the primary root may receive the
BPDU with a higher priority and then loose its place, which causes network topology
change errors. Due to the erroneous change, the traffic supposed to travel over the
high-speed link may be pulled to the low-speed link and congestion will occur on the
network. Root protection function is used against such problem.
The root port and other blocked ports maintain their state according to the BPDUs send
by uplink switch. Once the link is blocked or encountering a faulty condition, the ports
cannot receive BPDUs and the switch will select root port again. In this case, the former
root port will turn into a BDPU specified port and the former blocked ports will enter into
a forwarding state, as a result, a link loop will be generated.
The security functions can control the generation of loop. After it is enabled, the root
port cannot be changed, the blocked port will maintain in “Discarding” state and do not
forward packets, thus to avoid link loop.
You can use the following command to configure the security functions of the switch.
Perform the following configuration in corresponding views.
Table1-16 Configure the switch security function
Operation Command
Configure switch BPDU protection (from system view) stp bpdu-protection
Restore the disabled BPDU protection state, as defaulted, (from
system view). undo stp bpdu-protection
Configure switch Root protection (from Ethernet port view) stp root-protection

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Operation Command
Restore the disabled Root protection state, as defaulted, (from
Ethernet port view) undo stp root-protection
Configure switch loop protection function (from Ethernet port view) stp loop-protection
Restore the disabled loop protection state, as defaulted (from
Ethernet port view) undo stp loop-protection
After configured with BPDU protection, the switch will disable the edge port through
RSTP, which receives a BPDU, and notify the network manager at same time. Only the
network manager can resume these ports.
The port configured with Root protection only plays a role of a designated port.
Whenever such port receives a higher-priority BPDU when it is about to turn into
non-designated port, it will be set to a listening state and not forward packets any more
(as if the link to the port is disconnected). If the port has not received any higher-priority
BPDU for a certain period of time thereafter, it will resume to the normal state.
When configure a port, only one configuration can be effective among loop protection,
Root protection and Edge port configuration at same moment.
By default, the switch does not enable loop protection, BPDU protection or Root
protection.
For detailed information about the configuration commands, refer to the Command
Manual.
1.3 Display and Debug RSTP
After the above configuration, execute display command in any view to display the
running of the RSTP configuration, and to verify the effect of the configuration. Execute
reset command in user view to clear the statistics of RSTP module. Execute
debugging command in user view to debug the RSTP module.
Table1-17 Display and Debug RSTP
Operation Command
Display RSTP configuration information about the
local switch and the specified ports display stp [ interface interface-list ]
Clear RSTP statistics information reset stp [ interface interface-list ]
Enable RSTP (error/event/packet) debugging debugging stp { error | event |packet }
Disable RSTP debugging undo debugging stp { error | event | packet }