When an SRX300, SRX550HM, or SRX1500 Series device, 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.

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

For SRX300 Series, SRX1500 Series, and SRX550HM devices, when auto-negotiation is disabled, auto-MDI/MDI-X will also be disabled and the port will be an 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.

We have two options to solve this issue:

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

OR

2. 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.

• 2020-06-22: Changed "gigether-options no-auto-negotiation" to "ether-options no-auto-negotiation"

• 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.