Gigabit Ethernet Autonegotiation

Learn about Autonegotiation and how to configure Autonegotiation on Gigabit Ethernet Interfaces.

Gigabit Ethernet Autonegotiation Overview

Autonegotiation is enabled by default on all Gigabit Ethernet and Tri-Rate Ethernet copper interfaces. However, you can explicitly enable autonegotiation to configure remote fault options manually. When the autonegotiation is disabled, the speed has to be explicitly configured to 10–100 Mbps.

When you configure the Tri-Rate Ethernet copper interface to operate at 1 Gbps, autonegotiation must be enabled.

Configuring Gigabit Ethernet Autonegotiation

Configuring Gigabit Ethernet Autonegotiation with Remote Fault
Configuring Flow Control
Configuring Autonegotiation Speed on MX Series Routers
Displaying Autonegotiation Status

Configuring Gigabit Ethernet Autonegotiation with Remote Fault

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.

Configuring Flow Control

To enable flow control, include the flow-control statement at the [edit interfaces ge-fpc/pic>/port gigether-options] hierarchy level. For more information, see Configuring Flow Control.

Configuring Autonegotiation Speed on MX Series Routers

MX Series 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.

MX Series 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 on MX platform. This option does not support other MICs on MX platform.

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.

Note:

Starting in Junos OS Release 14.2, on MX Series 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.

Displaying Autonegotiation Status

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.

Table 1: Mode and Autonegotiation Status (Local)
Transmit	Receive	Mode	LED	Link	Autonegotiation Status
ON	ON	Default	Green	UP	Complete
ON	OFF	Default	Red	DOWN
OFF	ON	Default	Red	DOWN
OFF	OFF	Default	Red	DOWN
ON	ON	Default	Red	DOWN
ON	ON	Default	Green	UP	No-autonegotiation
ON	OFF	Default	Red	DOWN
OFF	OFF	Default	Red	DOWN
ON	ON	Default	Green	UP
ON	ON	Default	Red	DOWN
ON	ON	No-autonegotiation	Green	UP	Incomplete
ON	OFF	No-autonegotiation	Red	DOWN
OFF	ON	No-autonegotiation	Green	UP
OFF	OFF	No-autonegotiation	Red	DOWN
ON	ON	No-autonegotiation	Red	DOWN
ON	ON	Explicit	Green	UP	Complete
ON	OFF	Explicit	Red	DOWN
OFF	ON	Explicit	Red	DOWN
OFF	OFF	Explicit	Red	DOWN
ON	ON	Explicit	Red	DOWN
ON	ON	Explicit	Green	UP	No-autonegotiation
ON	OFF	Explicit	Red	DOWN
OFF	ON	Explicit	Green	UP
OFF	OFF	Explicit	Red	DOWN
ON	ON	Explicit	Red	DOWN
ON	ON	Explicit+RFI-Offline	Green	UP	Complete
OFF	ON	Explicit+RFI-Offline	Red	DOWN
OFF	OFF	Explicit+RFI-Offline	Red	DOWN
ON	ON	Explicit+RFI-Offline	Red	DOWN
ON	ON	Explicit+RFI-Offline	Green	UP	No-autonegotiation
ON	OFF	Explicit+RFI-Offline	Red	DOWN
OFF	ON	Explicit+RFI-Offline	Green	UP
OFF	OFF	Explicit+RFI-Offline	Red	DOWN
ON	ON	Explicit+RFI-Offline	Red	DOWN
ON	ON	Explicit+RFI-Offline	Red	DOWN	Complete
ON	OFF	Explicit+RFI-Offline	Red	DOWN
OFF	ON	Explicit+RFI-Online	Red	DOWN
OFF	OFF	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Green	UP	No-autonegotiation*
ON	OFF	Explicit+RFI-Online	Red	DOWN
OFF	ON	Explicit+RFI-Online	Green	UP
OFF	OFF	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Green	UP
ON	ON	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Red	DOWN	Complete
ON	OFF	Explicit+RFI-Online	Red	DOWN
OFF	ON	Explicit+RFI-Online	Red	DOWN
OFF	OFF	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Red	DOWN
ON	ON	Explicit+RFI-Online	Green	UP	Complete

Table 2: Mode and Autonegotiation Status (Remote)
Transmit	Receive	Mode	LED	Link	Autonegotiation Status
ON	ON	Default	Green	UP	Complete
ON	ON	Default	Red	DOWN
ON	OFF	Default	Red	DOWN
OFF	ON	Default	Red	DOWN
OFF	OFF	Default	Red	DOWN
ON	ON	No-autonegotiation	Green	UP	Incomplete
ON	ON	No-autonegotiation	Red	DOWN
ON	OFF	No-autonegotiation	Red	DOWN
OFF	ON	No-autonegotiation	Green	UP
OFF	OFF	No-autonegotiation	Red	DOWN
ON	ON	Explicit	Green	UP	Complete
ON	ON	Explicit	Red	DOWN
ON	OFF	Explicit	Red	DOWN
OFF	ON	Explicit	Red	DOWN
OFF	OFF	Explicit	Red	DOWN
ON	ON	Explicit	Red	DOWN	Complete
ON	OFF	Explicit	Red	DOWN
OFF	ON	Explicit	Red	DOWN
OFF	OFF	Explicit	Red	DOWN
ON	ON	Explicit+RFI-Offline	Red	DOWN	Complete
ON	OFF	Explicit+RFI-Offline	Red	DOWN
OFF	ON	Explicit+RFI-Offline	Red	DOWN
OFF	OFF	Explicit+RFI-Offline	Red	DOWN
ON	ON	Explicit+RFI-Online	Green	UP	Complete
ON	ON	Explicit+RFI-Online	Red	DOWN
ON	OFF	Explicit+RFI-Online	Red	DOWN
OFF	ON	Explicit+RFI-Online	Red	DOWN
OFF	OFF	Explicit+RFI-Online	Red	DOWN

Change History Table

Feature support is determined by the platform and release you are using. Use Feature Explorer to determine if a feature is supported on your platform.

Release

Description

14.2

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.

14.2

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Gigabit Ethernet Autonegotiation