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And if so, what is this feature called?

In a plant floor setting I would like to simplify the a printing systems for the maintenance folks.

Each station consists of a very small form factor Windows 7/10 PC and an Ethernet printer. The PC has a single Ethernet port and cannot be easily expanded to two.

Right now each PC and printer has an manually assigned network IP address. The installed printer drivers have ports assigned to the printer for that particular line and spare printer.

The problem comes when things get shifted do to repairs or testing. Over time as the number of units have increased it is getting harder to manage each station as replacing a computer or printer requires a lot of reconfiguration.

I would like to simplify the process by doing the following:

  1. Set the PC to DHCP and have the DHCP server set a fixed IP via the MAC.
  2. Set a secondary fixed address on the Ethernet card in all the computers to some public IP (Ex: 192.168.1.1)
  3. Set all the printers for all lines to the same address such on that network such as 192.168.1.2

This is the step I don't know if it can be done with a managed switch:

  1. Configure pairs of ports on the switch to separate VLANs so that each pair share the same 192.168.1.0 subnet. The means that the printer on port 2 and the printer on port 4 do not overlap because they are on separate VLANs but have the same address. We do not expect to be able to reach the printers from outside their paired PC.

  2. Allow the main LAN traffic on the network to reach the PC via its primary DHCP assigned address.

  3. Repeat on additional pairs of ports for additional stations.

This question is meant to determine if it this is a valid feature of smart manged switches or is strictly a routing problem.

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  • A managed switch will not help you. I can think of some convoluted ways to make this work, but they are more complicated than what you're doing now. What do you need to reconfigure besides the address of the printer?
    – Ron Trunk
    Jun 12, 2017 at 16:19
  • As far as the computer is concerned its making sure the right IP is in the driver configuration. Printing to another printer by accident would be very bad, Then there is the paper work that needs to be done to track it where those printer IPs are living.
    – Rich Shealer
    Jun 12, 2017 at 16:52
  • Can a Win 7/10 computer be configured for dhcp AND have a static secondary? I've never tried it.,
    – Ron Trunk
    Jun 12, 2017 at 17:01
  • Yes. In the IPV4 settings for the card there is an Advanced... button. On the dialog that opens you can set additional network addresses and gateways,
    – Rich Shealer
    Jun 12, 2017 at 17:17
  • @Run Trunk So you are saying that the switches generally prevent you from making VLANs with duplicate networks.
    – Rich Shealer
    Jun 12, 2017 at 17:18

1 Answer 1

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Your scenario seems plausible and possible. The switch should not have issues with the same subnet being used on multiple VLANs because it doesn't even look at the "Subnet" or Layer 3 contents of the frames. Its job is to just forward frames into their proper broadcast domains.

But of course if you are using multiple VLANs for each pair, the primary DHCP scopes must be separate for each VLAN and the DHCP setup will be the tricky part here since, you either need to have a VLAN interface and a DHCP helper/relay IP on each primary subnet for each VLAN.

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3
  • It looks like DHCP will be out. Windows 7 and up do not allow DHCP and a secondary IP address. The router that the switch connects to will not be able to resolve the subnet used by the printers, but that is desired. It will understand the computers primary address and that is desired.
    – Rich Shealer
    Jun 12, 2017 at 19:54
  • Yes, this whole scenario is only valid under the assumption that you can actually configure secondary addresses of your choice when the primary configuration is set to DHCP and not manual addressing. I had a feeling this wasn't possible in Windows 7 (or any Windows version for that matter)
    – Fahad Yousuf
    Jun 12, 2017 at 19:57
  • Since they already manually assign addresses it won't be too much of a hardship to continue and add the second address. DHCP was a wish list item..
    – Rich Shealer
    Jun 12, 2017 at 20:42

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