Configuring the Link Characteristics

By default, the router’s management Ethernet interface, fxp0 or em0, autonegotiates whether to operate in full-duplex or half-duplex mode. Fast Ethernet and J Series router Gigabit Ethernet interfaces can operate in either full-duplex or half-duplex mode, and all other interfaces can operate only in full-duplex mode. For Gigabit Ethernet, the link partner must also be set to full duplex.

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

Note: When you manually configure Fast Ethernet interfaces on the M Series and T Series routers, link mode and speed must both be configured. If both these values are not configured, the router uses autonegotiation for the link and ignores the user-configured settings.

To explicitly configure an Ethernet interface to operate in either full-duplex or half-duplex mode, include the link-mode statement at the [edit interfaces interface-name] hierarchy level: