Spirent SmartBits System, Reference Manual

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Appendix B: Auto Negotiation
10/100/1000Mbps Copper Ethernet Auto Negotiation
SmartBits System Reference 201
Auto Negotiation Priorities
When device interfaces have a range of capability levels, the highest performance mode is
selected based on the priority table shown in
Table 1 .
For 10/100Mbps Ethernet interfaces, the full-duplex 100Mbps mode of operation has the
highest priority of the available modes.
Fast Link Pulse (FLP) Signals
The auto negotiation protocol uses Fast Link Pulse (FLP) signals to exchange interface
information. These are a modified version of the Normal Link Pulse (NLP) signals that are
defined in the original 10BASE-T specifications and used to verify link integrity.
FLP signals are generated automatically at power-up. They are designed to coexist with
NLP signals, to ensure that a 10BASE-T device using NLP signals will continue to detect
link integrity even when it is attached to an auto negotiation hub sending FLP signals.
To ensure operation with interfaces that do not support Fast Link Pulses or auto
negotiation, as well as with older 10BASE-T interfaces that predate auto negotiation, the
AN protocol is designed to co-exist with non-AN interfaces. In these cases, the operating
mode used is that of the non-AN interface.
The auto negotiation management interface allows you to disable auto negotiation or to
manually force the negotiation process to take place. This enables you to select a specific
operational mode for a given device.
Auto negotiation is best viewed as one phase of the link initialization and verification
process. The following sections focus on the effects of having AN enabled or disabled, as
well as on how AN is handled in Spirent Communications applications.
Table C-1. Auto Negotiation Priority Table
Priority Level Description
A 100Base-T2 Full Duplex
B 100Base-TX Full Duplex
C 100Base-T2
D 100Base-T4 *
E 100Base-TX
F 10Base-T Full Duplex
G 10Base-T
* Not supported by SmartBits cards.