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[QFX] Disabling and enabling one VCP port is bringing down the second VCP port on QFX5100

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Article ID: KB33338 KB Last Updated: 25 Apr 2019Version: 1.0
Summary:

In a three-member Virtual Chassis setup (where one is a QFX5100-24s device), disabling and enabling one VCP port on the QFX5100-24s device is bringing down the other port, with a reboot required to recover both ports.

In this article, you understand the cause for the second port to go down and also learn about the solution to use to resolve the issue.

 

Symptoms:

The three-member Virtual Chassis setup consists of two QFX5100-96s devices and one QFX5100-24s device wherein port 100 from each QFX5100-96s device is connected to the QFX5100-24s device. When VC port 1/2 on QFX5100-24s is disabled and then enabled, port 1/3 is brought down and port 1/2 does not come up. 

{master:0}
QFX5100-VC> show virtual-chassis vc-port 
localre:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured          6    Up           40000        2   vcp-255/1/3
0/96        Configured          5    Up           40000        1   vcp-255/0/96
0/97        Configured          5    Up           40000        1   vcp-255/0/97
0/98        Configured          6    Up           40000        2   vcp-255/1/1
 
fpc1:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured          6    Up           40000        2   vcp-255/1/2
0/96        Configured          5    Up           40000        0   vcp-255/0/96
0/97        Configured          5    Up           40000        0   vcp-255/0/97
0/98        Configured          6    Up           40000        2   vcp-255/1/0
 
fpc2:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
1/0         Configured          6    Up           40000        1   vcp-255/0/98        
1/1         Configured          5    Up           40000        0   vcp-255/0/98  
1/2         Configured          6    Up           40000        1   vcp-255/0/100 
1/3         Configured          5    Up           40000        0   vcp-255/0/100
 
QFX5100-VC> request virtual-chassis vc-port delete pic-slot 1 port 2 member 2
fpc2:
--------------------------------------------------------------------------
Port deletion initiated, use cmd show virtual-chassis vc-port to verify

 
QFX5100-VC> show virtual-chassis vc-port    
localre:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured          6    Up           40000        2   vcp-255/1/3
0/96        Configured          5    Up           40000        1   vcp-255/0/96
0/97        Configured          5    Up           40000        1   vcp-255/0/97
0/98        Configured          6    Up           40000        2   vcp-255/1/1
 
fpc1:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured         -1    Down         40000
0/96        Configured          5    Up           40000        0   vcp-255/0/96
0/97        Configured          5    Up           40000        0   vcp-255/0/97
0/98        Configured         -1    Up           40000        2   vcp-255/1/0
 
fpc2:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
1/0         Configured         -1    Up           40000        1   vcp-255/0/98
1/1         Configured          5    Up           40000        0   vcp-255/0/98
1/3         Configured          5    Up           40000        0   vcp-255/0/100


{master:0}
QFX5100-VC> request virtual-chassis vc-port set pic-slot 1 port 2 member 2    
fpc2:
--------------------------------------------------------------------------
Port conversion initiated,  use show virtual-chassis vc-port to verify

 
{master:0}
QFX5100-VC> show virtual-chassis vc-port                                   
localre:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured         -1    Down         40000
0/96        Configured          5    Up           40000        1   vcp-255/0/96
0/97        Configured          5    Up           40000        1   vcp-255/0/97
0/98        Configured         -1    Up           40000        2   vcp-255/1/1
 
fpc1:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
0/100       Configured         -1    Down         40000
0/96        Configured          5    Up           40000        0   vcp-255/0/96
0/97        Configured          5    Up           40000        0   vcp-255/0/97
0/98        Configured         -1    Up           40000        2   vcp-255/1/0
 
fpc2:
--------------------------------------------------------------------------
Interface   Type              Trunk  Status       Speed        Neighbor
or                             ID                 (mbps)       ID  Interface
PIC / Port
1/0         Configured         -1    Up           40000        1   vcp-255/0/98
1/1         Configured         -1    Up           40000        0   vcp-255/0/98
1/2         Configured         -1    Down         40000
1/3         Configured         -1    Down         40000

 

Cause:

When an interface goes down (moved from VCP to normal ports), auto-channelization is triggered, which brings down these ports. 

 

Solution:

To resolve this problem, you can disable auto-channelization either entirely or only on the required ports.

  • Disable auto-channelization on the desired ports:

set chassis fpc <fpc-slot> pic <pic-slot> port <port-num> channel-speed disable-auto-speed-detection 
  • Disable auto-channelization entirely:

set chassis fpc <fpc-slot> auto-speed-detection disable

 

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