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[QFX] Actual speed of em0 interface not displayed in "show" output

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Article ID: KB35459 KB Last Updated: 05 Feb 2020Version: 1.0
Summary:

On QFX Series switches, the interface speed of a management port may not be reflected properly in the show command output due to a product limitation. This behavior is explained in this article and a workaround is also provided.

 

Symptoms:

The actual interface speed of the em0 port is not displayed in the show interfaces em0 output on QFX Series switches. For example, when the em0 port is connected to a 100m-speed peer, the port's speed is displayed as 1000 mbps even though the actual em0 interface speed is 100m.

A sample output is as follows:

test@QFX5100> show interfaces em0 extensive | match speed
  Type: Ethernet, Link-level type: Ethernet, MTU: 1514, Clocking: Unspecified, Speed: 1000mbps

In the show command output, the speed of the em0 interface is always shown to be a fixed value of 1000 mbps.

 

Cause:

This is a limitation on all platforms that run Junos VM on a CentOS/Linux host. Because the command output is coming from a virtual network port and not the physical interface, there is no support for changing the link speed of the virtual port.

 

Solution:

To check the actual speed, log in to the host shell and check the speed of the eth0 port.

Steps:

  1. Log in to the system as the root user.
  2. On Command Line Interface (CLI), issue the request app-engine host-shell or the hshell command in shell mode to get to the host shell.

root> request app-engine host-shell

root@QFX5100:RE:0% hshell
  1. Issue the ethtool eth0 command on the host shell and check the interface speed.
-sh-4.1# ethtool eth0
Settings for eth0:
            Supported ports: [ TP ]
            Supported link modes:   10baseT/Half 10baseT/Full
                                    100baseT/Half 100baseT/Full
                                    1000baseT/Full
            Supports auto-negotiation: Yes
            Advertised link modes:  10baseT/Half 10baseT/Full
                                    100baseT/Half 100baseT/Full
                                    1000baseT/Full
            Advertised pause frame use: Symmetric
            Advertised auto-negotiation: Yes
            Speed: 100Mb/s
            Duplex: Full
            Port: Twisted Pair
            PHYAD: 5
            Transceiver: internal
            Auto-negotiation: on
            MDI-X: Unknown
            Supports Wake-on: pumbg
            Wake-on: g
            Current message level: 0x00000003 (3)
            Link detected: yes

 

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