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[SRX] Auto-MDI/MDI-X is disabled when auto-negotiation is disabled

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Article ID: KB32053 KB Last Updated: 26 Mar 2020Version: 2.0
Summary:

When SRX300 Series, SRX550HM, SRX1500, and a PC are directly connected with a straight cable and auto-negotiation is off, the link will not go up.

This article explains the issue and offers two solutions.

 

Symptoms:

When SRX300 Series, SRX550HM, and SRX1500 Series devices and a PC are connected directly with a straight cable and auto-negotiation is off, the link does not go up.

 

Cause:

For SRX300 Series, SRX1500 Series and SRX550HM devices, when auto-negotiation is disabled, auto-MDI/MDI-X will also be disabled and port will be the MDI port. If the device (for example, a PC), which is connected to the SRX port, is also in MDI mode, the link will not go up by straight cable.

 

Solution:

We have two options to solve this issue.

 
  1. Use a crossover cable instead of a straight cable.

OR

 
  1. On Junos OS 15.1X49-D80 and later releases, a new command was added to forcibly enable the auto-MDI/MDI-X function. But this is valid only in the case of SRX300 Series and SRX550HM and not for SRX1500 Series devices.

#set interfaces ge-0/0/0 ether-options mdi-mode force
   
root# set interfaces ge-0/0/0 ether-options mdi-mode ?
Possible completions:
    auto                 Automatic mdi/mdi-x mode
    force                Enable auto-MDIX always

When the  force option is configured, auto-MDI/MDI-X will be enabled even if auto-negotiation is disabled.

 

Note: For SRX1500, the only solution would be to use a crossover cable instead of a straight cable.

 

Modification History:

2020-03-26: This issue is also seen for SRX1500 Series along with SRX300 series and SRX550MH. But the workaround introduced in Junos OS 15.1X49-D80 and later releases is not applicable for SRX1500 series.

 

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