• SGMII Auto-Negotiation (Cisco specification)
Auto-Negotiation provides a mechanism for transferring information from the local unit to the link
partner to establish speed, duplex and Master/Slave preference during a link session.
Auto-Negotiation is initiated upon any of the following conditions:
• Power up reset
• Hardware reset
• Software reset
• Restart Auto-Negotiation
• Transition from power down to power up
• The link goes down
The
10/100/1000BASE-T Auto-Negotiation
is based on Clause 28 and 40 of the IEEE 802.3
specification. It is used to negotiate speed, duplex and flow control over CAT5 (or higher) UTP
cable. Once Auto-Negotiation is initiated, the device determines whether or not the remote device
has Auto-Negotiation capability. If so, the device and the remote device negotiate the speed and
duplex with which to operate.
If the remote device does not have Auto-Negotiation capability, the device uses parallel detect
function to determine the speed of the remote device for 100BASE-TX and 10BASE-T modes. If a
link is established based on the parallel detect function, it is then required to establish the link at
half-duplex mode only. Refer to IEEE 802.3 clauses 28 and 40 for a full description of Auto-Nego-
tiation.
1000BASE-X Auto-Negotiation
is defined in Clause 37 of the IEEE 802.3 specification. It is used
to auto-negotiate duplex and flow control over fibre cable.
If one side of the link enables 1000BASE-X Auto-Negotiation and the link partner does not, the link
cannot linkup. The device implements an Auto-Negotiation bypass mode.
SGMII Auto-Negotiation
. SGMII is a de-facto standard designed by Cisco. SGMII uses 1000BASE-
X coding to send data as well as Auto-Negotiation information. However, the contents of the SGMII
Auto-Negotiation are different than the 1000BASE-X Auto-Negotiation.
Warning
If one device provides Auto-negotiation and the other works with a manual link parameters
setting (i.e. without Auto-negotiation) the link operates in half-duplex mode. If the manual
setting is set to full-duplex, the "Out collisions" may occur.
Speed / duplex
Ethernet link speed and duplex mode can be selected. Both parameters can be either auto negotiated
or set manually. When the Auto negotiation parameter is disabled, only manual setting of the speed
and duplex is possible. In most cases it is better to enable the auto negotiation and use "auto /
auto" speed and duplex settings.
There are two possibilities to force the link to operate in specific speed and duplex:
• Auto negotiation enabled. Select the desired Speed / duplex. The auto negotiation process ad-
vertises only this specified link mode. The link partner is asked to use it.
• Auto negotiation disabled. Select the desired Speed / duplex. The link is set to this specified link
mode. The link partner has to be set manually to the same mode.
Frame mode
Ethernet Frame mode control defines the expected Ingress and the generated Egress tagging frame
format for this port as follows:
• normal
Normal Network mode uses industry standard IEEE 802.ac Tagged or Untagged frames. Tagged
frames use an Ether Type of 0x8100. Ports that are expected to be connected to standard Ethernet
devices should use this mode
• DSA
Inactive options are not required.
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Configuration
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