In which configuration mode is name [region-name] used?

The name [region-name] command is entered in MST Config mode on Cisco IOS devices.

Spanning TreeMST Config

name [region-name]

Configures the Multiple Spanning Tree (MST) region name, which is required to group switches into the same MST region for interoperable MSTP operation.

Definition: name [region-name] is a Cisco IOS mst config command. Configures the Multiple Spanning Tree (MST) region name, which is required to group switches into the same MST region for interoperable MSTP operation.

Overview

The `name` command in MST configuration mode is used to assign a region name to the Multiple Spanning Tree (MST) region on a Cisco IOS switch. MSTP (IEEE 802.1s) extends Rapid Spanning Tree Protocol (RSTP) by allowing multiple spanning tree instances (MSTIs) to map to multiple VLANs, reducing the number of spanning tree instances needed in a large VLAN environment. The MST region is a logical grouping of switches that share the same region name, revision number, and VLAN-to-instance mapping.

Switches must have identical MST configuration to be considered part of the same region; otherwise, they will treat each other as separate regions and interoperate using Common Spanning Tree (CST). This command is critical when deploying MSTP because misconfigured region names cause switches to fall back to CST, leading to suboptimal forwarding paths and potential loops. You would use this command when migrating from PVST+ or Rapid PVST+ to MSTP to reduce spanning tree overhead, or when designing a large Layer 2 network with many VLANs.

The command is entered in MST configuration mode (reached via `spanning-tree mst configuration`). It modifies the running configuration immediately; the MST configuration is saved as part of the running config and must be saved to startup config to persist. The region name is case-sensitive and can be up to 32 characters.

A common mistake is forgetting to also set the revision number and VLAN-to-instance mapping, as all three must match across switches in the same region. The command does not require any special privilege level beyond privileged EXEC (enable) mode. The MST configuration is stored in a separate section of the running config and can be viewed with `show running-config | include mst` or `show spanning-tree mst configuration`.

When troubleshooting MSTP issues, verifying that the region name matches on all switches is the first step. The command itself does not produce output; its effect is seen in the MST configuration and spanning-tree behavior. The MST region name is also used in the BPDU exchange to identify region membership.

Syntax·MST Config

name [region-name]

When to Use This Command

When deploying MSTP in a campus network to define a consistent region name across all switches in the same MST region.
When migrating from Rapid PVST+ to MSTP to ensure all switches in the region share the same name and revision number.
When adding a new switch to an existing MST region, you must configure the same region name to avoid topology instability.
When troubleshooting MST region mismatches that cause spanning tree loops or blocked ports.

Parameters

Parameter	Syntax	Required	Description
region-name	WORD (1-32 characters)	Required	A case-sensitive alphanumeric string that identifies the MST region. All switches in the same MST region must have the same region name. Common practice is to use a descriptive name like 'Campus' or 'Region1'. Avoid spaces or special characters; using underscores or hyphens is acceptable. A common mistake is using different case or trailing spaces, which cause region mismatch.

Command Examples

Configuring MST region name

name CAMPUS_CORE

This command sets the MST region name to 'CAMPUS_CORE'. The name is case-sensitive and must match exactly on all switches in the same region. No output is generated upon successful configuration.

Verifying MST region configuration

show spanning-tree mst configuration

Name      [CAMPUS_CORE]
Revision  1     Instances configured 2
Instance  Vlans mapped
--------  ---------------------------------------------------------------------
0         1-9,11-99,101-199,201-4094
1         10,100,200

The output shows the configured MST region name 'CAMPUS_CORE', revision number (default 1), and the VLAN-to-instance mapping. Ensure the name matches other switches in the region.

Understanding the Output

The 'show spanning-tree mst configuration' command displays the MST region configuration. The 'Name' field shows the configured region name; it must be identical on all switches in the same MST region. The 'Revision' field is a number (0-65535) that must also match across the region.

The 'Instances configured' shows how many MST instances are active. The table lists each MST instance and the VLANs mapped to it. A mismatch in region name or revision will cause the switch to consider itself in a different region, leading to boundary ports and potential loops.

Configuration Scenarios

Configure MST Region Name on a Distribution Switch

A network administrator is migrating from Rapid PVST+ to MSTP to reduce spanning-tree instances. The distribution switch (DSW1) must be configured with an MST region name that matches the core switches.

Topology

DSW1(Gi0/1)---trunk---(Gi0/1)Core1
DSW1(Gi0/2)---trunk---(Gi0/2)Core2

Steps

1.Step 1: Enter global configuration mode: configure terminal
2.Step 2: Enter MST configuration mode: spanning-tree mst configuration
3.Step 3: Set the region name: name Campus
4.Step 4: (Optional) Set revision number: revision 1
5.Step 5: (Optional) Map VLANs to instances: instance 1 vlan 10-20
6.Step 6: Exit MST configuration mode: exit
7.Step 7: Verify configuration: show spanning-tree mst configuration

Configuration

! Enter MST configuration mode
spanning-tree mst configuration
 name Campus
 revision 1
 instance 1 vlan 10-20
 exit

Verify: show spanning-tree mst configuration Expected output includes: Name [Campus], Revision 1, Instance 1 Vlans mapped: 10-20

Watch out: If the region name does not match exactly (case-sensitive) on all switches, they will not form a common MST region, and CST will be used instead. Always copy-paste or carefully type the name.

Correcting MST Region Name Mismatch Between Switches

Two access switches (ASW1 and ASW2) are connected via trunk links but are not forming a single MST region. The network engineer suspects a region name mismatch.

Topology

ASW1(Gi0/1)---trunk---(Gi0/1)ASW2

Steps

1.Step 1: On ASW1, check current MST configuration: show spanning-tree mst configuration
2.Step 2: On ASW2, check current MST configuration: show spanning-tree mst configuration
3.Step 3: Compare region names. If different, on the switch with incorrect name, enter configuration mode: configure terminal
4.Step 4: Enter MST configuration mode: spanning-tree mst configuration
5.Step 5: Change the region name to match: name CorrectRegion
6.Step 6: Exit and verify: end, show spanning-tree mst configuration

Configuration

! On ASW2, correct the region name
configure terminal
spanning-tree mst configuration
 name CorrectRegion
 exit
end

Verify: show spanning-tree mst configuration Both switches should show: Name [CorrectRegion]. Also check 'show spanning-tree mst' to see that they are in the same region (region ID matches).

Watch out: Changing the region name resets the MST configuration? No, it only changes the name. However, if the revision number or VLAN mapping also differ, those must be corrected too. Use 'show spanning-tree mst configuration detail' to see full details.

Troubleshooting with This Command

When troubleshooting MSTP issues, the `name` command itself is not a show command, but its configuration is critical. The primary verification command is `show spanning-tree mst configuration`. Healthy output shows a consistent region name across all switches in the region.

If the region name is mismatched, the output will show different names, and the switches will not be in the same region. This can be identified by checking the 'MST region' field in `show spanning-tree mst`; if the region ID (a hash of name, revision, and mapping) differs, the switches are in different regions. Common symptoms of region mismatch include: unexpected blocking ports, loops, or suboptimal forwarding paths.

For example, if two switches are directly connected but one has region name 'Campus' and the other 'campus' (case difference), they will treat each other as separate regions and use CST, which may cause one link to block unnecessarily. To diagnose, follow this flow: 1) On each switch, run `show spanning-tree mst configuration` and note the Name, Revision, and Instance mapping. 2) Compare across switches; all must match exactly. 3) If mismatched, correct the configuration using the `name` command. 4) After correction, verify with `show spanning-tree mst` that the 'MST region' field shows the same hash. Additionally, use `debug spanning-tree mst events` to see region boundary changes.

Correlate with `show spanning-tree interface` to see port roles. If the region name is correct but other parameters differ, the region will still be inconsistent. The MST configuration is stored in NVRAM as part of the startup config; if a switch reloads with a different config, the region may break.

Always ensure all switches in the region have identical MST configuration. Another useful command is `show spanning-tree mst interface` to see per-instance port states. If a port is in 'boundary' role, it indicates the neighbor is in a different region or running a different STP variant.

This is a key indicator of region mismatch. In summary, the `name` command is a foundational piece of MSTP; without consistent naming, the entire MSTP domain fails to operate correctly.

CCNA Exam Tips

CCNA 200-301 exam expects you to know that MST region name, revision number, and VLAN-to-instance mapping must match on all switches in the same MST region.

A common exam scenario: two switches with different MST region names will treat the link as an MST boundary, reverting to PVST+ behavior on that port.

The 'name' command is configured in MST configuration mode, entered via 'spanning-tree mst configuration'.

Remember that the MST region name is case-sensitive and can be up to 32 characters.

Common Mistakes

Typing the region name with a typo or different case on different switches, causing them to be in different regions.

Forgetting to also set the revision number to match; the default revision is 1, but if one switch has a different revision, they will not form a single region.

Configuring the region name but not applying the configuration with 'exit' or 'end' to activate it.

name [region-name] vs instance [id] vlan [range]

Both the 'name' and 'instance' commands are configured in MST configuration mode and are essential for Multiple Spanning Tree Protocol (MSTP) operation. They are commonly confused because they both define MST region parameters, but they serve distinct purposes: 'name' sets the region identifier that must match across all switches in a region, while 'instance' maps VLANs to specific MST instances within that region.

Aspect	name [region-name]	instance [id] vlan [range]
Scope	Regional identity – applies to the entire MST region.	Per-instance mapping – applies to a specific MST instance (0-15).
Configuration mode	MST configuration mode (spanning-tree mst configuration).	Same MST configuration mode.
Persistence	Saved in running-config and startup-config as part of MST configuration.	Saved similarly; instance mappings are stored in the MST configuration block.
Precedence	Must match on all switches in the same MST region for interoperability.	Mapping is local to the region; mismatched mappings between regions are not compared (separate regions).
Typical use	Grouping switches into an MST region by assigning identical region names.	Creating MST instances (e.g., instance 1 vlan 10-20) to assign VLANs to different spanning tree topologies.

Use name [region-name] when you need to define or verify the MST region identity so that all switches in the same region share the same configuration and interoperate correctly.

Use instance [id] vlan [range] when you want to map a set of VLANs to a specific MST instance, enabling per-instance spanning tree behavior for load balancing or topology control.

Platform Notes

On Cisco IOS-XE (e.g., Catalyst 9000 series), the `name` command syntax is identical to classic IOS. The MST configuration mode is entered via `spanning-tree mst configuration`. The output of `show spanning-tree mst configuration` is similar but may include additional fields like 'MST config ID' in newer versions.

On NX-OS (e.g., Nexus 9000), the equivalent command is `spanning-tree mst configuration` followed by `name <region-name>`. However, NX-OS uses a different configuration hierarchy: you must first enter `configure terminal`, then `spanning-tree mst <instance>`, but the region configuration is done under `spanning-tree mst configuration` as well. The syntax is: `spanning-tree mst configuration` -> `name <region-name>`.

NX-OS also requires a revision number. On ASA firewalls, MSTP is not supported; they use PVST+ or Rapid PVST+ if at all. On IOS-XR (e.g., ASR 9000), MSTP is not supported; instead, use REP or other Layer 2 protocols.

There are no significant differences between IOS 12.x, 15.x, and 16.x for this command; the behavior is consistent. However, in IOS 15.0 and later, the MST configuration can be applied without reloading the switch. In earlier versions, some platforms required a reload after changing MST configuration?

Actually, no reload is required; the configuration takes effect immediately. One nuance: on some older IOS versions (12.2), the MST configuration mode might not be available unless the switch runs the appropriate IP services or advanced IP services image. Always verify the feature set supports MSTP.

The command is available on most Catalyst switches (2960, 3560, 3750, 4500, 6500) and ISR routers with Layer 2 switching modules. On routers, MSTP is supported only if the router has a switch module (e.g., EtherSwitch module).

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