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Configuring the Link Characteristics on Ethernet Interfaces

Full-duplex communication means that both ends of the communication can send and receive signals at the same time. Half-duplex is also bidirectional communication, but signals can flow in only one direction at a time.

By default, the router’s management Ethernet interface, fxp0 or em0, autonegotiates whether to operate in full-duplex or half-duplex mode. J Series Gigabit Ethernet interfaces and Fast Ethernet interfaces, except the J Series ePIM Fast 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 and 10-Gigabit Ethernet, the link partner must also be set to full duplex.

Note: For M Series, MX Series, and most T Series routers, the management Ethernet interface is fxp0. For TX Matrix Plus routers and T1600 routers configured in a routing matrix, the management Ethernet interface is em0.

Note: Automated scripts that you have developed for standalone T1600 routers (T1600 routers that are not in a routing matrix) might contain references to the fxp0 management Ethernet interface. Before reusing the scripts on T1600 routers in a routing matrix, edit the command lines that reference the fxp0 management Ethernet interface so that the commands reference the em0 management Ethernet interface instead.

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

Note: On a J Series ePIM Fast Ethernet interface, if you specify half-duplex (or if full-duplex mode is not autonegotiated), the following message is written to the system log: "Half-duplex mode not supported on this PIC, forcing full-duplex mode."

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.

Note: Member links of an aggregated Ethernet bundle must not be explicitly configured with a link mode. You must remove any such link-mode configuration before committing the aggregated Ethernet configuration.

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:

[edit interfaces interface-name]link-mode (full-duplex | half-duplex);
 

Related Documentation

 

Published: 2012-12-11

Supported Platforms

 

Related Documentation

 

Published: 2012-12-11

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