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My company has our printers provided by a contractor via a managed service. The contractor has software installed in our network which is supposed to detect the printers and then report back on the print volumes. This software is not working therefore, I took a look at the logs and discovered that the software was scanning the IP range that of the server (where the software is installed) and not other VLANS in the network (where the printers are).

The service provider asked me to send the address ranges for the printers therefore, I sent the below list:

╔══════════════════════════════╦═══════════════════════════════╗
║ Konica Minolta - C625DS      ║ 10.10.108.13                  ║
║ Konica Minolta C280          ║ 10.10.200.10                  ║
║ Konica Minolta - C625DS      ║ 10.10.104.10                  ║
║ HP LaserJet P2055dn          ║ 10.10.104.11                  ║
║ HP LaserJet P2055dn          ║ 10.10.106.13                  ║
║ Konica Minolta C280          ║ 10.10.106.10                  ║
║ Konica Minolta C280          ║ 10.10.206.10                  ║
║ Kyrocera FS-3040MFP+         ║ N/A     (MANUAL REPORT)       ║
║ HP LaserJet P2055dn          ║ 10.2.56.10 (MANUAL REPORT)    ║
║ HP LaserJet P2055dn          ║ 192.168.20.10 (MANUAL REPORT) ║
║ Konica Minolta C280          ║ 10.10.102.10                  ║
║ Fuji Xerox DocuCentre SC2020 ║ 10.10.210.10                  ║
║ Konica Minolta C452          ║ 10.10.102.11                  ║
╚══════════════════════════════╩═══════════════════════════════╝

The service provider replied, asking for the subnets also.

Please help me to understand what he was asking for. I do not understand the difference between a VLAN and a subnet.

Is he looking for the subnet mask? What would my answer possibly look like?

pgunston
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  • Also: [How does IPv4 Subnetting work?](http://serverfault.com/questions/49765/how-does-ipv4-subnetting-work). – EEAA Nov 27 '15 at 00:25
  • Have you considered asking the service provider what they meant? – womble Nov 27 '15 at 00:33
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    "What is a subnet" is "opinion-based"? o_O - they want to know how many addresses to scan to find all printers. To know how big the networks address ranges where the printers are, are. The first one, Konica Minolta - C625DS is on 10.10.108.13. Is that in a network range going from `10.10.108.1 through 10.10.108.255`? The subnet is /24 or 255.255.255.0. Is it from `10.10.108.0 - 10.10.111.254`? The subnet is /22 or 255.255.252.0. The answers will be /NN or roughly 255.255.NN.NN. You could look at the printer configuration, the subnet for each one will be configured with the IP address. – TessellatingHeckler Nov 27 '15 at 01:13

2 Answers2

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I do not understand the difference between a VLAN and a subnet.

A VLAN is a layer 2 construct. Putting devices on separate VLANS is like connecting them to different physical switches. Devices on separate VLANS cannot communicate directly with each other.

A subnet is a layer 3 IP construct.

Frequently VLANS and subnets are deployed in a 1:1 relationship, but that does not necessarily need to be the case.

In your situation, the vendor is essentially asking for the subnet mask for each entry in your table. This will allow them to scan the entire subnet, not just a single IP address.

EEAA
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Short answer

Probably the provider is asking for the netmask, yes.

Long answer

A subnet is a "filter" you give to your network interface to allow only certain IPs to communicate with you, even if they are connected to your same physical switch.

A VLAN is something like a virtual switch: it permits having several collision domains in the same physical switch, allowing you to configure different subnets in each VLAN.

Technically you can set up different subnets in the same VLAN (or physical switch), but is hard to imagine a good reason to do it.

So it looks like the provider has to configure a "subnet" field in their software to make it able to scan all the possible addresses, and that's what he's asking for :-)

jac
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