Gigabit Ethernet Autonegotiation

To configure explicit autonegotiation and remote fault, include the auto-negotiation statement and the remote-fault option at the [edit interfaces ge-fpc/pic/port gigether-options] hierarchy level.

Routers with Combo Line Rate DPCs and Tri-Rate Copper SFPs support autonegotiation of speed. The autonegotiation specified interface speed is propagated to CoS, routing protocols, and other system components. Half-duplex mode is not supported.

Routers with IQ2 PICs connected to other devices require matching auto-negotiation configurations for both the PIC and for the device in order to achieve link up.

To specify the autonegotiation speed, use the speed (auto | 1Gbps | 100Mbps | 10Mbps | auto-10m-100m) statement at the [edit interfaces ge-fpc/pic/port] hierarchy level.

To set port speed negotiation to a specific rate, set the port speed to 1Gbps, 100Mbps, or 10Mbps. If the negotiated speed and the interface speed do not match, the link will not be brought up.

If you set the autonegotiation speed auto option, then the port speed is negotiated.

Starting from Junos OS Release 14.2, theauto-10m-100m option allows the fixed tri-speed port to auto negotiate with ports limited by 100m or 10mmaximum speed. This option must be enabled only for Tri-rate MPC port, that is, 3D 40x 1GE (LAN) RJ45 MIC.

You can disable auto MDI/MDIX using the no-auto-mdix statement at the [edit interfaces ge-fpc/pic/port gigether-options] hierarchy level.

Use the show interfaces ge-fpc/pic/port brief command to display the auto negotiation of speed and auto MDI/MDIX states.

Starting in Junos OS Release 14.2, on routers with Tri-rate Enhanced DPC (DPCE-R-40GE-TX), when you configure the interface speed using the auto-10m-100m option, the speed is negotiated to the highest value possible (100 Mbps), if the same value is configured on both sides of the link. However, when you view the interface speed of the DPC, using the show interfaces command, the value of the speed is not accurately displayed. For instance, if you configure the speed of the Tri-rate enhanced DPC, as 100Mbps on both sides of the link, the interface speed of the DPC is negotiated to 100 Mbps. However, the interface speed of the DPC displays 1 bps. This is an issue with the show interfaces command only. The actual interface speed is 100 Mbps.

To display Gigabit Ethernet interface details, including the autonegotiation status, use the operational mode command show interfaces ge- fpc/pic/port extensive.

Table 1 and Table 2 provide information about the autonegotiation status on local and remote routers with fiber interfaces. The status of the link and LED can vary depending on the level of autonegotiation set and the transmit and receive fiber status.