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auto-negotiation

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 7.6.

Statement introduced in Junos OS Release 9.0 for EX Series switches.

Statement introduced in Junos OS Release 12.2 for ACX Series Universal Metro Routers.

Description

For Gigabit Ethernet interfaces on M Series, MX Series, T Series, TX Matrix routers, and ACX Series routers explicitly enable autonegotiation and remote fault. For EX Series switches, explicitly enable autonegotiation only.

  • auto-negotiation—Enables autonegotiation. This is the default.

  • no-auto-negotiation—Disable autonegotiation. When autonegotiation is disabled, you must explicitly configure the link mode and speed.

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

Note

On EX Series switches, an interface configuration that disables autonegotiation and manually sets the link speed to 1 Gbps is accepted when you commit the configuration; however, if the interface you are configuring is a Tri-Rate Ethernet copper interface, the configuration is ignored as invalid and autonegotiation is enabled by default.

To correct the invalid configuration and disable autonegotiation:

  1. Delete the no-auto-negotiation statement and commit the configuration.
  2. Set the link speed to 10 or 100 Mbps, set no-auto-negotiation, and commit the configuration.

On EX Series switches, if the link speed and duplex mode are also configured, the interfaces use the values configured as the desired values in the negotiation. If autonegotiation is disabled, the link speed and link mode must be configured.

Note

On T4000 routers, the auto-negotiation command is ignored for interfaces other than Gigabit Ethernet.

Note

On ACX Series routers, when you configure fiber interfaces (fiber media mode) to operate at 1 Gbps, autonegotiation is enabled by default to negotiate the speed and duplex settings. You can disable autonegotiation by using the (no-auto-negotiation) statement, and commit the configuration. in the fiber media mode. In copper interfaces (copper media mode), autonegotiation is enabled by default. To disable autonegotiation, you need to explicitly configure the link speed to 10 or 100 Mbps, set no-auto-negotiation, and commit the configuration.

Default

Autonegotiation is automatically enabled. No explicit action is taken after the autonegotiation is complete or if the negotiation fails.

Options

remote-fault (local-interface-online | local-interface-offline)—(Optional) For M Series, MX Series, T Series, TX Matrix routers, and ACX Series routers only, manually configure remote fault on an interface.

Default: local-interface-online

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.