4–2
MULTILINK ML810 MANAGED EDGE SWITCH – INSTRUCTION MANUAL
AUTO-CROSS(MDIX) AND AUTO-NEGOTIATION, FOR RJ-45 PORTS
CHAPTER 4: OPERATION
4.2
Auto-Cross(MDIX) and Auto-negotiation, for RJ-45
ports
The RJ-45 ports independently support auto-cross (MDI or MDIX) in auto-negotiation mode
and will work properly with all the other connected devices with RJ-45 ports whether they
support Auto-negotiation (e.g 10Mb Hub, media converter) or fixed mode at 10Mb or
100Mb Half/Full Duplex(managed switch) or not. No cross-over cable is required while
using the ML810’s copper port to other devices. Operation is according to the IEEE 802.3u
standard.
The Managed ML810’s Fast Ethernet copper ports can be set for either fixed 100Mb speed
or for 10/100 F/H N-way auto-negotiation per the IEEE802.3u standard. The selection is
made via MNS software. The factory default setting is for auto-negotiation. At 10Mb or
100Mb-fixed speed, the user may select half- or full-duplex mode by MNS Software for
each RJ-45 port separately. For detail information See Section 2.3 of this manual for
information to access the “6K-MNS Software user guide”
One frequently-used application for the Managed Multilink ML810 Switch copper ports is to
connect one of them using a fiber media converter to another Switch in the network
backbone, or to some other remote 100Mb device. In this case, it is desirable to operate
the fiber link at 100Mb speed, and at either half- or full duplex mode depending on the
capabilities of the remote device. Standard commercially available Fast Ethernet media
converters mostly do not support auto-negotiation properly, and require that the switched
port to which they are connected be at the 100Mb fixed speed. Attachments to a 10/100
auto-negotiation port typically will not work properly. The ML810 Switch’s RJ-45 ports
handle this situation by configuring the ports as per desired through MNS software port
settings and can check the port status of each port after the change.
When Multilink ML810 RJ-45 copper ports are set for auto-negotiation and are connected
to another auto-negotiating device, there are 4 different speed and F/H modes possible
depending on what the other device supports. These are: (1) 100Mb full-duplex, (2) 100Mb
half-duplex, (3) 10 Mb full-duplex and (4) 10 Mb half-duplex.
The auto-negotiation logic will attempt to operate in descending order and will normally
arrive at the highest order mode that both devices can support at that time. (Since auto-
negotiation is potentially an externally controlled process, the original “highest order
mode” result can change at any time depending on network changes that may occur). If
the device at the other end is not an auto-negotiating device, the ML810’s RJ-45 ports will
try to detect its idle signal to determine 10 or 100 speed, and will default to half-duplex at
that speed per the IEEE standard.
General information:
Auto-negotiation per-port for 802.3u-compliant switches occurs when:
• the devices at both ends of the cable are capable of operation at either 10Mb or
100Mb speed and/or in full- or half-duplex mode, and can send/receive auto-
negotiation pulses, and...
• the second of the two connected devices is powered up*, i.e., when LINK is
established for a port, or...
• the LINK is re-established on a port after being lost temporarily.
NOTE
Note
Some NIC cards only auto-negotiate when the computer system that they are in is
powered. These are exceptions to the “negotiate at LINK – enabled” rule above, but may
be occasionally encountered.
