For Juniper Networks EX or QFX Series switches, the following article details steps to verify whether an IRB (called VLAN interface on legacy platforms) interface is up, and the steps to troubleshoot when it is down.

To verify a Physical Interface or an Aggregated Ethernet Interface (LAG), refer to KB22217 - Resolution Guides - EX - Troubleshoot/Verify Interface [juniper.net].

• Troubleshoot an integrated routing and bridging (IRB) or virtual local area network (VLAN) interface that is down.

• An IRB or VLAN interface is not coming up (both terms are used interchangeably).

Perform the following steps:

1. Run the following command to display the 'Admin' status of the IRB or VLAN interface:

Legacy: show interfaces <vlan interface> terse

ELS: show interfaces <irb interface> terse

Example

ELS

root@switch> show interfaces irb.15 terse
Interface               Admin Link Proto    Local                 Remote
irb.15                  up    up   inet     192.168.0.1/24

Legacy

root@switch> run show interfaces vlan.10 terse
Interface  Admin   Link  Proto   Local      Remote
vlan.10    up      up    inet    10.0.0.1/24 

What is the "Admin" status of the IRB interface?

• Up - This means that the IRB Layer 3 Sub-Interface is Administratively Enabled. Continue to Step 3.

• Down - If the Admin status of the IRB Interface is Down, then Continue to Step 2.

2. The interface is Administratively Down, which means that the administrator of this switch disabled the interface.

root@switch> show interfaces vlan.30 terse
Interface  Admin   Link  Proto  Local      Remote
vlan.30   down    down  inet   10.0.0.1/24 

This can be confirmed with the following command:

show configuration interfaces <vlan interface> | display set

Example

root@switch# show interfaces vlan.30 | display set
set interfaces vlan unit 30 disable
set interfaces vlan unit 30 family inet address 10.0.0.1/24

 Bring the interface Administratively Up by enabling the interface with the following command:

ELS: delete interfaces irb unit <number> disable

Legacy: delete interfaces vlan unit <vlan id> disable

Example

Legacy: root@switch# delete interfaces vlan unit 30 disable

ELS:    root@switch# delete interfaces irb unit 15 disable 

Important Note: We strongly recommend that you check with the network administrator before issuing this command, as it will alter the network topology.

Continue with Step 3 (when the VLAN interface is Administratively Up).

3. What is the "Link" status of the VLAN interface?

root@switch> show interfaces vlan.10 terse
Interface  Admin    Link  Proto   Local      Remote
vlan.10    up      up    inet    10.0.0.1/24 

• Up: End of workflow. Your IRB interface is up. See other helpful commands and links.

• Down: Continue to Step 4.

4. Run the following command to verify that the physical interfaces are correctly mapped to the VLAN:

show vlans <VLAN Name> 

Example

root@switch> show vlans DATA-1
Name           Tag     Interfaces
DATA-1         10     
                       ae0.0, ge-0/0/0.0*, ge-0/0/3.0, ge-0/0/10.0

Are all the physical interfaces listed?

• Yes - Continue to Step 5.

• No - Add the physical interfaces as shown in the above example: 

root@switch# set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members DATA-1 

OR

root@switch# set vlans TEST interface ge-0/0/0 

For more information on Layer 3 Subinterfaces, refer to Understanding Integrated Routing and Bridging.

5. Verify that the interfaces are active with the following command:

show vlans <vlan>

Example

root@switch> show vlans TEST

Name Tag Interfaces
TEST 30
ge-0/0/0.0*, ge-0/0/1.0

Asterisk "*" denotes the active connection for the interface/Switch Port.

In the above example, interface ge-0/0/0 has a client detected, but ge-0/0/1 does not.

Is there an ( * ) on at least one physical interface of that VLAN?

• Yes: End of Workflow. Your IRB is up. See other helpful commands and links.

Note: If an ( * ) is found next to the physical interface, but that VLAN interface is still down, then contact your technical support representative.

• No: To make an IRB or VLAN Interface active, at least one physical interface has to be up on the VLAN.

  An expected Physical Interface has a physical connection, but it is not detected. To fix this, proceed with the following Resolution Guide for all the Physical Interfaces that do NOT have an ( * ) : KB19797 - Resolution Guide - EX - Troubleshoot Physical Interface [juniper.net].

Then your IRB or VLAN should be up.

*If you got any issues with configuration change, please rollback the config by the command, "rollback 1" and commit. 
For the details of rollback command, you can refer to the document below:

https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/command/rollback.html

Other Helpful Commands 

show ethernet-switching interfaces

2020-05-20: ​Article reviewed for accuracy, no changes required; article accurate and valid.
2022-09-27: Specified that this article applies both to legacy and devices with support for ELS, including QFX Series devices
2024-08-02: Added ELS platforms in category
2026-05-28: Added rollback command