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[EX] How to link up Juniper Ethernet switching GbE copper port by RJ45 loopback connector

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The EX series GbE copper ports has the ability to support 10/100/1000BASE-T. But, by default, the copper port will not link up by inserting a RJ45 loopback connector. This article provides a sample configuration for EX switching and the RJ45 pinout to solve this request.

As the EX GbE copper port supports 10/100/1000M speed, testing whether a port can link up or not through a RJ45 loopback connector, is the easiest way for some customers. This article provides information on how to test a EX GbE copper interface via the RJ45 loopback connector.

Instructions to link up EX GbE copper port in 100M fixed speed.

A 100base-T RJ45 loopback connector, whether made or bought, should look similar to the diagram shown below:

RJ45 loopback connector

To link up a copper GbE interface from EX series, disable auto-negotiation and set the speed to 100Mbps.The excerpt below is a sample configuration to link up ge-0/0/14 with a RJ45 loopback connector:
lab# show interfaces ge-0/0/14 | display set
set interfaces ge-0/0/14 ether-options no-auto-negotiation
set interfaces ge-0/0/14 ether-options link-mode full-duplex
set interfaces ge-0/0/14 ether-options speed 100m
set interfaces ge-0/0/14 unit 0 family ethernet-switching
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