# Set Up Speed and Duplex

In the default mode, an Intel® PRO/100 adapter or Intel® Gigabit Network 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. 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.

Your link partner must match the setting you choose.

| NOTES: You cannot change the speed or duplex of Intel adapters that use fiber cabling. Per the IEEE specification, gigabit speed cannot be forced. It can only be auto-negotiated.

# Configuring Speed and Duplex in Microsoft* Windows*

By default, auto-negotiation is enabled. Change this setting only to match your link partner.

1. Navigate to the Device Manager.

2. Open Properties on the adapter you would like to configure.

3. Click the Link Speed tab.

4. Select the appropriate speed and duplex from the Speed and Duplex pull down menu.

5. Click OK.

## Intel® Gigabit Network Adapter Considerations

If auto-negotiation is disabled, the adapter will not operate at gigabit speed (1000 Mbps).

Per the IEEE specification, gigabit speed is available only in full-duplex.

Fiber-based adapters operate only in full duplex, and only at their native speed.

`Last modified on 12/11/07 4:27p Revision 9`