This article explains how to verify that the Physical Interface of an EX switch is UP, and to troubleshoot it if it is not.
To verify an Aggregated Ethernet Interface (LAG) or an IRB interface (called VLAN interface in legacy platforms), refer to KB22217 - Resolution Guides - EX - Troubleshoot/Verify Interface [juniper.net] .
Goals
Troubleshoot a Physical Interface that is down.
Verify that the Physical Interface is up.
Below is an example of a Physical Interface that is up. The following points are verified and corrected in the step-by-step solution below.
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up up <<<< Physical Interface ge-0/0/0.0 up up eth-switch <<<< Subinterface (Logical Interface)
In the above output:
The Physical Interface (ge-0/0/0) is Administratively Up and the Link is also Up.
The Subinterface (ge-0/0/0.0) is Administratively Up and the Link is also Up.
The correct family is assigned to the Subinterface (ge-0/0/0.0).
Perform the following steps:
Run the following command to view the status of the Physical Interface and the Subinterface (Logical Interface):
show interfaces <interface> terse
Note: This command output is going to be used throughout this article.
Example: root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down <<<<<< ge-0/0/0.0 up down eth-switch
Example:
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down <<<<<< ge-0/0/0.0 up down eth-switch
What is the 'Admin' status of the Physical interface (i.e. ge-0/0/0 in the example)?
Up - Jump to Step 3 .
Down - Continue to Step 2 .
Expected Interface is not listed - Consult KB22218 - [EX/QFX] Physical Interface is not listed in 'show interface' command output [juniper.net] .
The interface is Administratively Down, which means that the administrator of this switch disabled the interface.
Example: root@EX4600# run show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 down down ge-0/0/0.0 up down eth-switch This can be confirmed with the operational command: show configuration interfaces <Interface Name> | display set Example: root@EX4600# show interfaces ge-0/0/0 | display set set interfaces ge-0/0/0 disable set interfaces ge-0/0/0 unit 0 family ethernet-switching
root@EX4600# run show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 down down ge-0/0/0.0 up down eth-switch
This can be confirmed with the operational command:
show configuration interfaces <Interface Name> | display set
root@EX4600# show interfaces ge-0/0/0 | display set set interfaces ge-0/0/0 disable set interfaces ge-0/0/0 unit 0 family ethernet-switching
Bring the interface Administratively Up by enabling the interface with the command:
# delete interfaces <Interface Name> disable Example: root@EX4600# delete interfaces ge-0/0/0 disable Important Note : We strongly recommend that you check with the network administrator before issuing this command, as it will alter the network topology.
# delete interfaces <Interface Name> disable
root@EX4600# delete interfaces ge-0/0/0 disable
Important Note : We strongly recommend that you check with the network administrator before issuing this command, as it will alter the network topology.
For more information about disabling Physical Interfaces, refer to Disabling a Physical Interface .
Continue with Step 3 (when the interface is Administratively Up).
What is the 'Link' status of the Physical interface (i.e. ge-0/0/0)?
Example: root@EX4600# run show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down <<<<< ge-0/0/0.0 up down eth-switch
root@EX4600# run show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down <<<<< ge-0/0/0.0 up down eth-switch
Up - Jump to Step 9 and perform the Subinterface (Logical interface) check. Down - Continue to Step 4.
Up - Jump to Step 9 and perform the Subinterface (Logical interface) check.
Down - Continue to Step 4.
Display the interface speed and duplex settings with the command:
root@EX4600> show interfaces ge-0/0/0 extensive | match “duplex|speed” Example: root@ex4600> show interfaces ge-0/0/0 extensive | match "duplex|speed" Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Speed: 1000mbps, Link mode: Full-duplex, Flow control: None, Remote fault: OK, Link partner Speed: 1000 Mbps
root@EX4600> show interfaces ge-0/0/0 extensive | match “duplex|speed”
root@ex4600> show interfaces ge-0/0/0 extensive | match "duplex|speed" Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Speed: 1000mbps, Link mode: Full-duplex, Flow control: None, Remote fault: OK, Link partner Speed: 1000 Mbps
Are the speed and duplex settings still set to 'auto'? Yes - Continue to Step 5 . No - If Speed/Duplex have been configured, make sure that the configuration of the EX port matches the far-end/peer port settings. You can also configure duplex and speed manually with the following commands: set interfaces <interface name> speed 1g set interfaces <interface name> ether-options no-auto-negotiation set interfaces <interface name> ether-options link-mode full-duplex . If this resolves the issue, contact Juniper Support . If it is not resolved, continue to Step 5 .
Are the speed and duplex settings still set to 'auto'?
set interfaces <interface name> speed 1g set interfaces <interface name> ether-options no-auto-negotiation set interfaces <interface name> ether-options link-mode full-duplex .
If this resolves the issue, contact Juniper Support . If it is not resolved, continue to Step 5 .
Confirm whether the cable is connected to the port.
If you have physical access to the EX switch, verify that the cable is connected to the affected interface. Make sure that the link light is on for that interface to confirm that the cable is firmly seated. (Try unplugging and re-plugging if possible.) Perform a physical loopback test as described in Performing Loopback Testing for Fast Ethernet and Gigabit Ethernet Interfaces .
If you do not have physical access, use J-Web to identify the interface connectivity. The port will be green if the Physical Link is detected.
If another working port is available, does the same cable work in another working port?
Yes - Suspect bad port. Contact your technical support representative .
No - Continue to Step 7.
Does the link come up with another working (known good) cable?
Suspect cable could have gone bad. Try with a different cable. Perform Cable Test to make sure that it is not a cable issue: [CLI Procedure] Diagnosing a Faulty Twisted-Pair Cable [JWeb Procedure] Troubleshooting Interface Configuration and Cable Faults Yes - Replacing the cable fixed the issue. The physical interface is up. Jump to Step 9 to perform the Subinterface (Logical interface) check. No - Continue to Step 8.
Suspect cable could have gone bad.
Try with a different cable.
Perform Cable Test to make sure that it is not a cable issue:
[CLI Procedure] Diagnosing a Faulty Twisted-Pair Cable
[JWeb Procedure] Troubleshooting Interface Configuration and Cable Faults
Yes - Replacing the cable fixed the issue. The physical interface is up. Jump to Step 9 to perform the Subinterface (Logical interface) check.
No - Continue to Step 8.
View the logs for any errors with the following command:
root@EX4600> show log messages | match <Interface Name>
If the reason for the physical link being down cannot be resolved, contact your technical support representative .
[Subinterface Check] Continue to look at the output of show interfaces <interface name> terse , and check the Sub interface (i.e. ge-0/0/0.0).
show interfaces <interface name> terse
Now observe the Subinterface line output (i.e. ge-0/0/0.0 in the example):
Example: root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down ge-0/0/0.0 up down eth-switch <<<<<<< Subinterface (Logical Interface)
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up down ge-0/0/0.0 up down eth-switch <<<<<<< Subinterface (Logical Interface)
Is the Subinterface/ Unit mapped to the correct Protocol family (Layer 2 = 'eth-switch' and Layer 3 = 'Inet' ) ? Yes - Continue to Step 10. No - Configuration issue. For more information about Protocol Family, refer to family (for EX Series switches) . The Logical Interface is not listed (ge-0/0/0.0 ).
Is the Subinterface/ Unit mapped to the correct Protocol family (Layer 2 = 'eth-switch' and Layer 3 = 'Inet' ) ?
Yes - Continue to Step 10.
No - Configuration issue. For more information about Protocol Family, refer to family (for EX Series switches) .
The Logical Interface is not listed (ge-0/0/0.0 ).
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up up ge-0/0/0.16386 up up Seeing the unit 16386 means that the Logical/Subinterface (unit 0) for this Physical Interface (ge-0/0/0) has not been defined. On Legacy platforms, there would be no listed subunits. Verification: root@EX4600# show interfaces | display set | match ge-0/0/0 There is nothing configured under the interface ge-0/0/0 hierarchy.
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up up ge-0/0/0.16386 up up
Seeing the unit 16386 means that the Logical/Subinterface (unit 0) for this Physical Interface (ge-0/0/0) has not been defined. On Legacy platforms, there would be no listed subunits.
Verification:
root@EX4600# show interfaces | display set | match ge-0/0/0
There is nothing configured under the interface ge-0/0/0 hierarchy.
Solution : root@EX4600# set interfaces ge-0/0/0 unit 0 family ethernet-switching
Solution :
root@EX4600# set interfaces ge-0/0/0 unit 0 family ethernet-switching
What is the 'Admin' status of the Subinterface (Logical Interface)?
Example: root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up up ge-0/0/0.0 up down eth-switch <<<<
root@EX4600> show interfaces ge-0/0/0 terse Interface Admin Link Proto Local Remote ge-0/0/0 up up ge-0/0/0.0 up down eth-switch <<<<
Down - Enable the logical interface with the command as discussed in Step 2 .
Up - End of workflow - Your Physical Interface has been verified as Up. For example:
The Physical Interface (ge-0/0/0) is Administratively Up and the Link is Up. The Subinterface (ge-0/0/0.0) is Administratively Up and the Link is Up. The correct family has been assigned to the Subinterface (ge-0/0/0.0).
The Physical Interface (ge-0/0/0) is Administratively Up and the Link is Up.
The Subinterface (ge-0/0/0.0) is Administratively Up and the Link is Up.
The correct family has been assigned to the Subinterface (ge-0/0/0.0).
Technical Documentation
Network Interfaces for EX Series Switches:
2020-02-25: Article reviewed for accuracy; links updated
2022-03-11: Article updated to reflect ELS terminology, changes and additional steps