Auto-Negotiation enables a pair of link partners to communicate whenever either interface is initialized, reset, or reconfigured and to discover an optimal set of mutually supported capabilities.
There are two separate Auto-Negotiation technology families: twisted-pair interfaces and 1000BASE-X interfaces.
Twisted-pair Ethernet interfaces can automatically negotiate transmission speed, half- or full–duplex operation, and use of flow control. In addition, 1000BASE-T and 100BASE-T2 interfaces can negotiate master/slave roles.
1000BASE-X interfaces can automatically negotiate half- or full-duplex operation and the use of flow control.
Both families can use Auto-Negotiation messages to describe a fault or to report vendor- or product-specific ...