No Network - No Server

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Network Connectivity for your server ...

Connectivity to a "Network server" is a misnomer all servers are on a network...

And all networks are not created equal.

Network speed is dependent on the slowest NIC speed and the switch / hub.

Note: This article is for Wired Ethernet connectivity only. There are other types of network topologies but most of them are irrelevant now.

NIC Link Speeds and Duplex are:

  • 10 Half Duplex
  • 10 Full Duplex
  • 100 Half Duplex
  • 100 Full Duplex
  • 1000 Half Duplex
  • 1000 Full Duplex

The difference between Half Duplex and Full Duplex is that Half Duplex can not transmit and receive at the same time. That is the NIC has two states: Send or Receive. Where as  Full Duplex can do both at the same time.

Need a server? You can build your own!

80% of connectivity problems are the Half / Full duplex settings. Why? Because most NIC and Operating System software is set for Auto Duplex Negotiation (Automatic negotiation) when installed. If you have one NIC set to Half Duplex on your network the switch / hub will take that as default and all ports on the switch / hub will be set for Half Duplex (it is mind numbing that the NIC and switch/hub manufactures still use this protocol). So if you are having connection problems check the speed / duplex setting on the effected NIC.

What happens when most of the NIC's on your network are 100 / Full and one reverts to 10 / Half Duplex the NIC the 10 / Half Duplex will drop 'Packets'. Dropped packets means that the NIC at 10 / Half Duplex has to negotiate the connection every time it needs to send or receive data on the network. This negotiation will cause the previously transmitted packet to be dropped, causing the transmitting NIC to resend the packet .

This is an old IT cartoon from the Main Frame days when system outage would take days to repair...When you install a switch / hub it may or may not have software to setup the parameters of the device. If you do have software one of the parameters you should set is the speed / duplex. I force all my NIC's to 100/1000 Full Duplex.

As you can see a misbehaving NIC can cause the overall speed of the network to degrade, sometimes it will be so bad that none of the computers on the network will communicate reliably with any other computer.

If you have older computers / NIC's you may want to consider setting all of them to 100 / Full Duplex and not use the Auto Negotiate at all.

With newer computers / NIC's there will be a choice to set the NIC to 1 GBPS (1000 MBPS) / Full Duplex. You can do this but if you have one device that the fastest speed is 100 MBPS (such as a network printer) even with a 'Smart Switch' your overall network speed will 100 / Full Duplex.

What is a 'Smart Switch'?

A Smart Switch is a hub that has from 4 to 48 ports and the hardware has the ability to switch between the listed link speeds above. Do they always work? No. Smart Switches take the incoming speed / duplex and set the parameters for that specific port. This is software it is not hardwired in the device and all it takes is one NIC sending 10 / 100 / 1000 Half Duplex to the switch to reset all the ports. This is one reason to not use the Auto Negotiation software.

If you use a Domain Controller to set the machine GP for the NIC you can force all computers to a set speed and duplex. However devices such as printers, scanners, and other non operating system devices will not use a GPO and those will have to be set manually.

Note: Most small routers such as the Linksys or Netgear are hardwired for speed and duplex at 100 / Full, any computer or NIC connected at any other speed / duplex will cause network connectivity problems.

If you are interested in setting up a network I have a e-book that may interest you - Build a Server Guide and network connectivity.



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