ALCATEL - Spanning Tree
Platforms Supported : OmniSwitch 6860, 6860E
TO RESET SPANNING TREE TO DEFAULT, THERE IS NO COMMAND LIKE "no spantree ...", CONFIGURE AGAIN THE DEFAULT VALUE, EG :
"By default, the bridge priority value is set to 32768 for the CIST, an MSTI, and a VLAN instance".
SpanTree Priority
Configures the bridge priority value for the Common and Internal Spanning Tree (CIST) instance, a Multiple Spanning Tree Instance (MSTI), or a VLAN instance. This command is also used to configure the priority value for a port or link aggregate associated with the CIST, an MSTI, or a VLAN.
spantree [cist | msti msti_id | vlan vlan_id] [port chassis/ slot/port[-port2] | linkagg linkagg_id [-linkagg_id2]] priority priority
Syntax Definitions
- cist
- The CIST instance (also known as MSTI 0). This parameter is configurable in both modes (flat or per-VLAN).
- msti_id
- An existing MSTI ID number. If MSTI 0 is specified, the priority applies to the CIST instance. This parameter is configurable in both modes (flat or per-VLAN) but only if the flat mode protocol is set to MSTP.
- vlan_id
- An existing VLAN ID number. This parameter is configurable in both modes (flat or per-VLAN).
- chassis
- The chassis identifier.
- slot/port[-port2]
- The slot number and port number of the physical port. Use a hyphen to specify a range of ports.
- linkagg_id[-linkagg_id2]
- The link aggregate ID number. Use a hyphen to specify a range of IDs (10-20).
- priority
- A bridge or port priority value. The valid range for the bridge priority is 0–65535. The valid range for the port priority is 0–15. If MSTP is the active flat mode protocol, enter a value that is a multiple of 4096 (for example, 4096, 8192, 12288).
parameter default cist | msti msti_id | vlan vlan_id cist
Defaults
- By default, the bridge priority value is set to 32768 for the CIST, an MSTI, and a VLAN instance.
- By default, the port or link aggregate priority value is set to 7.
Usage Guidelines
- The bridge priority is used to determine which bridge the Spanning Tree algorithm designates as the
root bridge. The port priority value is used to determine the most favorable port when a bridge has multiple ports with the same path cost to the root bridge.
- The lower the bridge or port priority number assigned, the higher the priority that is associated with the
bridge or port.
- If none of the optional instance parameters (cist, msti, or vlan) or port and linkagg parameters are
specified with this command, the bridge priority is configured for the CIST instance by default. This is true regardless of which mode (flat or per-VLAN) is active for the switch.
- Although the cist, msti, and vlan parameters are configurable in both the flat and per-VLAN mode, the
specified priority values are not applied unless the supporting mode (flat for CIST/MSTI or per-VLAN for a VLAN instance) is active.
- To configure the bridge priority with this command, specify the instance (cist, msti, or vlan) and the
priority value; do not specify a port number or link aggregate ID.
- The bridge priority value for an MSTI is calculated by adding the configured priority value to the
Spanning Tree instance number. For example, if the priority value of MSTI 10 equals 32768 (the default), then the Spanning Tree priority value advertised for this instance is 32770 (32768 + 10).
- When the protocol is changed to/from MSTP, the bridge priority for the flat mode CIST instance is
reset to the default value.
- The bridge priority specifies the priority value for the first two octets of the Bridge ID (eight octets
long). The remaining six octets of the Bridge ID contain a dedicated bridge MAC address. In regards to the priority for an MSTI, only the four most significant bits are used.
- To configure the port priority with this command, specify the instance (cist, msti, or vlan), a port
number or link aggregate ID that is associated with that instance, and the priority value.
- The port priority value configured with this command is only applied to the specified instance. As a
result, a single port can have different priority values for each instance. For example, in flat mode, port 1/24 can have a priority value of 7 for MSTI 2 and a priority value of 5 for MSTI 3.
- The port priority specifies the value of the priority field contained in the first byte of the port ID. The
second byte contains the physical switch port number.
Examples
The following command examples set the bridge priority for the specified instance:
-> spantree priority 8192 -> spantree cist priority 8192 -> spantree vlan 2 priority 32679 -> spantree msti 1 priority 2500 ERROR: Valid bridge priority values are multiples of 4096: 0, 4096, 8192, 12288, 16384 ... 61440 -> spantree msti 1 priority 8192
The following command examples set the port priority for the specified instance:
-> spantree port 1/1/10 priority 10 -> spantree cist port 1/1/10 priority 10 -> spantree cist linkagg 10 priority 1 -> spantree vlan 200 port 2/1/1 priority 15 -> spantree vlan 2 linkagg 5 priority 2 -> spantree msti 2 port 1/1/24 priority 5 -> spantree msti 3 linkagg 6-8 priority 10
Enabling/Disabling Spanning Tree on a Port
Spanning Tree is automatically enabled on all eligible ports. When Spanning Tree is disabled on a port, the port is put in a forwarding state for the specified instance.
For example, if a port is associated with both VLAN 10 and VLAN 20 and Spanning Tree is disabled on the port for VLAN 20, the port state is set to forwarding for VLAN 20. However, the VLAN 10 instance still controls the port state as it relates to VLAN 10. This example assumes the switch is running in the per-VLAN Spanning Tree mode.
If the switch is running in the flat Spanning Tree mode, then disabling the port Spanning Tree status applies across all VLANs associated with the port. The flat mode instance is specified as the instance associated with the port, even if the port is associated with multiple VLANs.
To change the port Spanning Tree status for a VLAN instance regardless of which mode (per-VLAN or flat) is active for the switch, use the enable Spanning Tree on port 8/1 for VLAN 10 and disable STP on port 6/2 for VLAN 20 :
-> spantree vlan 10 port 8/1 enable -> spantree vlan 20 port 6/2 disable
To change the port Spanning Tree status for the flat mode instance, use the that this command is available when the switch is running in either mode (per-VLAN or flat). For exam- ple, the following command disables the Spanning Tree status on port 1/24 for the flat mode instance :
-> spantree cist port 1/24 disable
