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HP 5500 Ei 5500 Si Switch Series Configuration Guide

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•  You can configure the current device as the root bridge by setting the device priority to 0. For the 
device priority configuration, see  Configuring the device priority. 
Configuring the current device as the root bridge of a specific 
spanning tree 
To configure the current device as the root bridge of a specific spanning tree:  
Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Configure the current device 
as the root bridge. 
• In STP/RSTP mode: 
stp root primary 
• In PVST mode: 
stp vlan  vlan-list  root primary  
• In MSTP mode: 
stp  [ instance  instance-id  ] root 
primary  Use one of the commands. 
By default, a device does not 
function as the root bridge. 
 
Configuring the current device as
 a secondary root bridge of a 
specific spanning tree 
To configure the current device as a secondary root bridge of a specific spanning tree:  
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Configure the current 
device as a secondary root 
bridge. 
• In STP/RSTP mode: 
stp root secondary 
• In PVST mode: 
stp vlan  vlan-list  root secondary  
• In MSTP mode: 
stp  [ instance  instance-id  ] root secondary  Use one of the 
commands. 
By default, a device does 
not function as a 
secondary root bridge. 
 
Configuring the device priority 
 
 
CAUTION: 
•
  Yo u  c a n n o t  c h a n g e  t h e  p r i o r i t y  o f  a  d e v i c e  a f t e r  i t  i s  c o n f i g u re d  a s  t h e  ro o t  b r i d g e  o r  a s  a  s e c o n d a r y  ro o
t
bridge.   
•   During root bridge selection, if all devices in a spanning tree have the same priority, the one with the 
lowest MAC address will be selected as the root bridge of the spanning tree. 
 
Device priority is a factor in spanning tree calculation. The priority of a device determines whether the 
device can be elected as the root bridge of a spanning tree. A lower numeric value indicates a higher 
priority. You can set the priority of a device to a low value to specify the device as the root bridge of the 
spanning tree. A spanning tree device can have different priorities in different MSTIs. 
To configure the priority of a device in a specified MSTI:
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    							 81 
 
Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Configure the priority of 
the current device. 
• In STP/RSTP mode: 
stp priority  priority 
• In PVST mode: 
stp vlan  vlan-list  priority  priority  
• In MSTP mode: 
stp  [ instance  instance-id  ] priority priority Use one of the commands.
 
The default setting is 
32768. 
 
Configuring the maximum hops of an MST region 
By setting the maximum hops of an MST region, you can restrict the region size. The maximum hops 
configured on the regional root bridge will be used as the maximum hops of the MST region. 
Configuration BPDUs sent by the regional root bridge always have a hop count set to the maximum value. 
When a device receives this configuration BPDU, it decrements the hop count by 1, and uses the new hop 
count in the BPDUs that it propagates. When the hop count of a BPDU reaches 0, it is discarded by the 
device that received it. This prevents devices beyond the reach of the maximum hop from participate in 
spanning tree calculation, so the size of the MST region is limited. 
Make this configuration on the root bridge only. 
All other devices in the MST region use the maximum 
hop value set for the root bridge. 
To configure the maximum number of hops of an MST region: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Configure the maximum hops 
of the MST region.  stp max-hops 
hops  20 by default.
 
 
Configuring the network diameter of a switched 
network 
Any two terminal devices in a switched network ar e connected through a specific path composed of a 
series of devices. The network diameter is the number of devices on the path composed of the most 
devices. The network diameter is a parameter that indicates the network size. A bigger network diameter 
indicates a larger network size. Based on the network diameter you configured, the system automatically 
sets an optimal hello time, forward delay, and max age for the device. 
To configure the network diameter of a switched network: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A
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Step Command Remarks 
2.  Configure the network 
diameter of the switched 
network. • In STP/RSTP/MSTP mode: 
stp bridge-diameter  diameter  
• In PVST mode: 
stp vlan  vlan-list  bridge-diameter  diameter  Use one of the 
commands. 
The default setting is 7. 
 
 
NOTE: 
•  In STP/RSTP/MSTP mode, each MST region is considered as a device and the configured network 
diameter is effective only for the CIST (or the common root bridge), but not for MSTIs. 
•   In PVST mode, the network diameter configurat ion is effective on the root bridge only. 
 
Configuring spanning tree timers 
The following timers are used for spanning tree calculation: 
•  Forward delay 
It is the delay time for port state transition. To  prevent temporary loops on a network, the spanning 
tree sets an intermediate port state, the learning st ate, before it transitions from the discarding state 
to the forwarding state, and requires that the port transitions its state afte r a forward delay timer to 
make sure that the state transition of the lo cal port keeps synchronized with the peer.  
•   Hello time 
The device detects whether a link failure has occu rred with the hello time interval. The spanning 
tree sends a configuration BPDU every hello time in terval. If the device receives no configuration 
BPDUs within the hello time interval,  it recalculates the spanning tree. 
•   Max age 
In the CIST of an MSTP network or each VLAN  of a PVST network, the device uses the max age 
parameter to determine whether a configuration BPDU received by a port has expired. If a port 
receives a configuration BPDU that has expired,  that MSTI must be re-calculated. The max age 
timer is ineffective for MSTIs.  
To avoid frequent network changes, be sure that  the settings of the hello time, forward delay and 
max age timers meet the following formulas:  
{  2 × (forward delay – 1 second)  ƒ max age 
{  Max age ƒ  2 × (hello time + 1 second) 
HP does not recommend you to manually set the spanning tree timers. Instead, you can specify the 
network diameter and let spanning tree protocols  automatically calculate the timers based on the 
network diameter. If the network diameter uses the defa ult value, the timers also use their default values. 
Configure the timers on the root bridge only, and the ti mer settings on the root bridge apply to all devices 
on the entire switched network. 
Configuration restrictions and guidelines 
•   The length of the forward delay timer is related to the network diameter of the switched network. The 
larger the network diameter is, the longer the fo rward delay time should be. If the forward delay 
timer is too short, temporary redundant paths migh t occur. If the forward delay timer is too long, 
network convergence might take a long time. HP recommends you to use the default setting.
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•  An appropriate hello time setting enables the device to quickly detect link failures on the network 
without using excessive network resources. If the  hello time is too long, the device will mistake 
packet loss as a link failure and trigger a new spanni ng tree calculation process. If the hello time is 
too short, the device will frequently send the same configuration BPDUs, which adds the device 
burden and wastes network resources. HP recommends you to use the default setting. 
•   If the max age timer is too short, the device wi ll frequently begin spanning tree calculation and 
might mistake network congestion as a link failure.  If the max age timer is too long, the device might 
fail to quickly detect link failures and begin s panning tree calculations, reducing the auto-sensing 
capability of the network. HP recommends you to use the default setting. 
Configuration procedure 
To configure the spanning tree timers:  
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Configure the forward 
delay timer. 
• In STP/RSTP/MSTP mode: 
stp timer forward-delay  time 
• In PVST mode: 
stp vlan  vlan-list  timer forward-delay 
time   Optional. 
Use one of the commands. 
The default setting is 15 
seconds.  
3.
  Configure the hello timer. 
• In STP/RSTP/MSTP mode: 
stp timer hello time  
• In PVST mode: 
stp vlan  vlan-list  timer hello  time  Optional. 
Use one of the commands. 
The default setting is 2 
seconds. 
 
4.  Configure the max age 
timer. 
• In STP/RSTP/MSTP mode: 
stp  timer max-age  time 
• In PVST mode: 
stp  vlan  vlan-list  timer max-age  time  Optional. 
Use one of the commands. 
The default setting is 20 
seconds.
 
 
Configuring the timeout factor 
The timeout factor is a parameter used to decide the  timeout time, in the following formula: Timeout time 
= timeout factor × 3 × hello time. 
After the network topology is stabilized, each non-root-bridge device forwards configuration BPDUs to 
the downstream devices at the interval of hello time to determine whether any link is faulty. If a device 
does not receive a BPDU from the upstream device within nine times the hello time, it assumes that the 
upstream device has failed and starts a new spanning tree calculation process. 
Sometimes a device might fail to receive a BPDU from the upstream device because the upstream device 
is busy. If a spanning tree calculation occurs, the calculation can fail and also waste network resources. 
In a stable network, you can prevent undesired spanning  tree calculations by setting the timeout factor to 
5, 6, or 7. 
To configure the timeout factor: 
 
Step Command Remarks 
1.   Enter system view. 
system-view N/A
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Step Command Remarks 
2.  Configure the timeout factor of the 
device.   stp timer-factor 
factor  3 by default.
 
 
Configuring the maximum port rate 
Th e  m a xi mu m  ra t e  o f  a  p o r t  re fe r s  t o  t h e  m a xi m u m  nu m b e r  o f  B PD Us  t h e  p o r t  c a n  s e n d  wi t h i n  e a ch  h e l l o  
time. The maximum rate of a port is related to the ph ysical status of the port and the network structure. 
The higher the maximum port rate is, the more BPDUs  will be sent within each hello time, and the more 
system resources will be used. By setting an approp riate maximum port rate, you can limit the rate at 
which the port sends BPDUs and prevent spanning tr ee protocols from using excessive network resources 
when the network becomes unstable. HP recommends you to use the default setting. 
To configure the maximum rate of a port or a group of ports: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Enter interface view or port 
group view. 
• Enter Layer 2 Ethernet interface view or 
Layer 2 aggregate interface view: 
interface interface-type 
interface-number 
• Enter port group view: 
port-group manual  port-group-name Use one of the commands.
3.
  Configure the maximum rate 
of the ports.   stp transmit-limit
 limit   10 by default.
 
 
Configuring edge ports 
If a port directly connects to a user terminal rather  than another device or a shared LAN segment, this 
port is regarded as an edge port. When network to pology change occurs, an edge port will not cause 
a temporary loop. Because a device does not determ ine whether a port is directly connected to a 
terminal, you must manually configure the port as an edge port. After that, the port can transition rapidly 
from the blocked state to the forwarding state. 
Configuration restrictions and guidelines 
•   If BPDU guard is disabled, a port set as an edge  port will become a non-edge port again if it 
receives a BPDU from another port. To  restore the edge port, re-enable it. 
•   If a port directly connects to a user terminal, configure it as an edge port and enable BPDU guard 
for it. This enables the port to transition to th e forwarding state quickly while ensuring network 
security. 
•   You cannot configure edge port settings and loop guard on a port at the same time. 
Configuration procedure 
To specify a port or a group of ports as edge port or ports:
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Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Enter interface view or port 
group view. 
• Enter Layer 2 Ethernet interface view or 
Layer 2 aggregate interface view: 
interface interface-type 
interface-number  
• Enter port group view: 
port-group manual  port-group-name Use one of the commands.
3.
  Configure the current ports as 
edge ports.   stp 
edged-port enable   All ports are non-edge ports 
by default.
 
 
Configuring path costs of ports 
Path cost is a parameter related to the rate of a port . On a spanning tree device, a port can have different 
path costs in different MSTIs. Setting appropriate pat h costs allows VLAN traffic flows to be forwarded 
along different physical links, achieving VLAN-based load balancing. 
You can have the device automatically calculate the default path cost, or you can configure the path cost 
for ports. 
Specifying a standard for the device to use when it calculates 
the default path cost 
 
  CAUTION: 
If you change the standard that the device uses to calculate the default path costs, you restore the path 
costs to the default. 
 
You can specify a standard for the device to use in automatic calculation for the default path cost. The 
device supports the following standards: 
•
  dot1d-1998 —The device calculates the default path cost for ports based on IEEE 802.1d-1998. 
•   dot1t —The device calculates the default path cost for ports based on IEEE 802.1t.  
•   legacy —The device calculates the default path cost for ports based on a private standard. 
Tabl e  14  sho
 ws the mappings between the link speed and the path cost.  
Table 14  Mappings between the link speed and the path cost 
Link speed  Port type  Path cost
 
IEEE 802.1d-1998 IEEE 802.1t  Private standard  
0 N/A  65535  200,000,000 
200,000 
10 Mbps Single port 
100 2,000,000 2000 
Aggregate interface 
containing 2 Selected ports
 1,000,000 1800 
Aggregate interface 
containing 3 Selected ports
 666,666 1600
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Link speed  Port type Path cost 
IEEE 802.1d-1998 IEEE 802.1t  Private standard  
Aggregate interface 
containing 4 Selected ports
 500,000 1400 
100 Mbps Single port 
19 200,000 200 
Aggregate interface 
containing 2 Selected ports
 100,000 180 
Aggregate interface 
containing 3 Selected ports
 66,666 160 
Aggregate interface 
containing 4 Selected ports
 50,000 140 
1000 Mbps 
Single port 
4 20,000 20 
Aggregate interface 
containing 2 Selected ports
 10,000 18 
Aggregate interface 
containing 3 Selected ports
 6666 16 
Aggregate interface 
containing 4 Selected ports
 5000 14 
10 Gbps Single port 
2 2000 2 
Aggregate interface 
containing 2 Selected ports
 1000 1 
Aggregate interface 
containing 3 Selected ports
 666 1 
Aggregate interface 
containing 4 Selected ports
 500 1 
 
Configuration restrictions and guidelines 
•
  When it calculates path cost for an aggregate inte rface, IEEE 802.1t takes into account the number 
of Selected ports in its aggregation group, but  IEEE 802.1d-1998 does not. The calculation formula 
of IEEE 802.1t is: Path cost = 200,000,000/link speed (in 100 kbps), where link speed is the sum 
of the link speed values of the Selected ports in the aggregation group. 
•   When multiple ports operate at a rate higher than 10 Gbps and the standard for default path cost 
calculation is  dot1d-1998 or legacy, the path cost of a single port or an aggregate interface takes 
the smallest value. As a result, the forwarding pat h selected might not be optimal. To solve this 
problem, use  dot1t as the standard for default path cost calculation, or manually set the path cost 
for a port ( Configuring path costs of ports ).
   
Configuration procedure 
To specify a standard for the device to use when it calculates the default path cost:  
Step Command Remarks 
1.  Enter system view. 
system-view  N/A
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Step Command Remarks 
2.  Specify a standard for the 
device to use when it 
calculates the default path 
costs of its ports.  stp pathcost-standard
 
{  dot1d-1998  | dot1t  | legacy  }  Optional. 
legacy by default.
 
 
Configuring path costs of ports 
When the path cost of a port changes, the system re-c alculates the role of the port and initiates a state 
transition.  
To configure the path cost of ports: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Enter interface view or port 
group view. 
• Enter Layer 2 Ethernet interface view or 
Layer 2 aggregate interface view: 
interface interface-type 
interface-number  
• Enter port group view: 
port-group manual  port-group-name Use one of the commands.
3.
  Configure the path cost of the 
ports. 
• In STP/RSTP mode: 
stp cost  cost 
• In PVST mode: 
stp vlan  vlan-list  cost cost 
• In MSTP mode: 
stp  [ instance  instance-id  ] cost  cost  Use one of the commands.
 
By default, the system 
automatically calculates the 
path cost of each port.
 
 
Configuration example 
# In MSTP mode, specify the device to calculate  the default path costs of its ports by using IEEE 
802.1d-1998, and set the path cost of GigabitEthernet 1/0/3 to 200 on MSTI 2. 
 system-view 
[Sysname] stp pathcost-standard dot1d-1998 
[Sysname] interface gigabitethernet 1/0/3 
[Sysname-GigabitEthernet1/0/3] stp instance 2 cost 200 
# In PVST mode, specify the device to calculate  the default path costs of its ports by using IEEE 
802.1d-1998, and set the path cost of GigabitEthernet 1/0/3 to 2000 on VLANs 20 through 30. 
 system-view 
[Sysname] stp mode pvst 
[Sysname] stp pathcost-standard dot1d-1998 
[Sysname] interface gigabitethernet 1/0/3 
[Sysname-GigabitEthernet1/0/3] stp vlan 20 to 30 cost 2000
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Configuring the port priority 
When the priority of a port changes, MSTP re-calculates the role of the port and initiates a state transition. 
The priority of a port is an important factor in de termining whether the port can be elected as the root 
port of a device. If all other conditions are the same, the port with the highest priority will be elected as 
the root port. 
On a spanning tree device, a port can have different priorities and play different roles in different 
spanning trees, so that data of different VLANs can be propagated along different physical paths, 
implementing per-VLAN load balancing. You can set port  priority values based on the actual networking 
requirements. 
To configure the priority of a port or a group of ports: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Enter interface view or 
port group view. 
• Enter Layer 2 Ethernet interface view or Layer 2 
aggregate interface view: 
interface interface-type interface-number  
• Enter port group view: 
port-group manual  port-group-name Use one of the 
commands.
 
3.  Configure the port 
priority. 
• In STP/RSTP mode: 
stp port priority  priority 
• In PVST mode: 
stp vlan  vlan-list  port priority  priority 
• In MSTP mode: 
stp  [ instance  instance-id  ] port priority priority  Use one of the 
commands. 
The default setting is 
128.
 
 
Configuring the port link type 
A point-to-point link directly connects two devices.  If two root ports or designated ports are connected 
over a point-to-point link, they can rapidly transition to the forwarding state after a proposal-agreement 
handshake process. 
Configuration restrictions and guidelines 
•   You can configure the link type as point-to-point  for a Layer 2 aggregate interface or a port that 
operates in full duplex mode. HP recommends you to use the default setting and let the device to 
automatically detect the port link type. 
•   The stp point-to-point force-false  or stp point-to-point force-true  command configured on a port in 
MSTP or PVST mode is effective for all MSTIs or VLANs.  
•   If the physical link to which the port connects is not a point-to-point link but you set it to be one, the 
configuration might bring a temporary loop. 
Configuration procedure 
To configure the link type of a port or a group of ports:
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Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Enter interface view or 
port group view. 
• Enter Layer 2 Ethernet interface view or Layer 
2 aggregate interface view: 
interface interface-type interface-number  
• Enter port group view: 
port-group manual  port-group-name Use one of the 
commands.
 
3.  Configure the port link 
type.   stp point-to-point 
{ auto  | force-false  | 
force-true  }  By default, the link type is 
auto
 where the port 
automatically detects the 
link type.  
 
Configuring the mode a port uses to 
recognize/send MSTP packets 
A port can receive/send MSTP pac kets in the following formats: 
•   dot1s —802.1s-compliant standard format 
•   legacy —Compatible format 
By default, the packet format recognition mode of a port is  auto. The port automatically distinguishes the 
two MSTP packet formats, and determines the format of packets that it will send based on the recognized 
format.  
You can configure the MSTP packet format on a port. When operating in MSTP mode after the 
configuration, the port sends and receives only MSTP packets of the format that you have configured to 
communicate with devices that send packets of the same format. 
MSTP provides MSTP packet format incompatibility guard. In MSTP mode, if a port is configured to 
recognize/send MSTP packets in a mode other than  auto, and if it receives a packet in a format different 
from the specified type, the port becomes a designat ed port and remains in the discarding state to 
prevent the occurrence of a loop. 
MSTP provides MSTP packet format frequent change gu ard. If a port receives MSTP packets of different 
formats frequently, the MSTP packet format configuration contains errors. If the port is operating in MSTP 
mode, it will be shut down for protection. Ports disabled in this way can be re-activated after a detection 
interval. For more information about the detection interval, see  Fundamentals Configuration Guide. 
To configure the MSTP packet format to be supported on a port or a group of ports: 
 
Step Command Remarks 
1.   Enter system view. 
system-view  N/A 
2.  Enter interface view or 
port group view. 
• Enter Layer 2 Ethernet interface view or Layer 2 
aggregate interface view: 
interface interface-type interface-number  
• Enter port group view: 
port-group manual  port-group-name Use one of the 
commands.
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