# Set Up Speed and Duplex

In the default mode, an Intel® PRO/100 adapter or Intel® PRO/1000 adapter using copper connections will attempt to auto-negotiate with its link partner to determine the best setting. If the adapter cannot establish link with the link partner using auto-negotiation, you may need to manually configure the adapter and link partner to identical settings to establish link and pass packets. This should only be needed when attempting to link with an older switch that does not support auto-negotiation or one that has been forced to a specific speed or duplex mode.

The settings available when auto-negotiation is disabled are:

- 10 Mbps or 100 Mbps Full duplex (requires a full duplex capable link partner set to full duplex). The adapter can send and receive packets at the same time. You must set this mode manually (see below).

- 10 Mbps or 100 Mbps Half duplex (requires a link partner set to half duplex). The adapter performs one operation at a time; it either sends or receives. You must set this mode manually (see below).

| CAUTION: Only experienced network administrators should force speed and duplex manually.

Your link partner must match the setting you choose.

| NOTE: You cannot change the speed or duplex of Intel PRO/1000 adapters that use fiber cabling.

## Manually Configuring Duplex and Speed Settings

If your switch supports the NWay* standard, and both the adapter and switch are set to auto-negotiate, full duplex configuration is automatic, and no action is required on your part. Not all switches support auto-negotiation. Check with your network administrator to verify whether your switch supports this feature.

Configuration is specific to the driver you’re loading for your operating system. To set a specific Link Speed and Duplex mode, click the Table of Contents link to the appropriate operating system.

| CAUTION: The settings at the switch must always match the adapter settings. Adapter performance may suffer or your adapter may not operate if you configure the adapter differently from your switch.
| NOTE: Per the IEEE specification, gigabit speed cannot be forced. It can only be auto-negotiated.

`Last modified on 12/03/04 4:48p Revision 1`