Troubleshooting subnet filtering

Only macOS and iOS devices having trouble discovering the printers

Confirm the subnets match.

This applies only if you specified the subnets when setting up the DNS records (to restrict printer access per subnet or because the domain name ends in .local). If that's the case, there are different type of DNS records for macOS and iOS devices where the B and LB records are stored within a reverse lookup zone.

However, for this to work successfully the reverse lookup zone must exactly match the subnet of the device. For example, if you create DNS records for two subnets like and, then you can't use as a shortcut. See DNS Record Examples for more details on how this works.

My users can't see any printers in their printer list

Remember, only users (clients) in subnets listed in the printer.conf.toml file will see printers in their printer lists.

  • Before you create subnet filtering rules, make sure that all of the printers are visible from that particular subnet. If the printers are missing, run through the steps in Configure Mobility Print.
  • When you configure DNS Setup in from the Mobility Print Admin interface, make sure that you list all of the subnets and create the correct DNS records by running the DNS commands generated by the Mobility Print Admin interfaceserver. This creates the Reverse Lookup Zones and Conditional Forwarder needed for mMacOS and iOS clients to work with Subnet Filtering. To see how the records should look, take a look at Mobility Print DNS Record Examples.
  • Do the subnets precisely match the subnets used by the clients on the network? If you create subnet filtering rules for two subnets, for example and, you cannot use as a shortcut.

Editing the printer.conf.toml file doesn't seem to do anything

After editing the file, did you remember to restart the Mobility Print service? When you look at the Mobility Print Admin Interface, changes should show immediately. Subnets are listed below each printer.

After editing the printer.conf.toml I received a "There was an error reading the printer config file" message

Does the printer.conf.toml revert back to the template every time you restart the Mobility Print server? Double-check that the rules follow the correct formatting and syntax (including spaces!). If there are formatting or syntax errors, the file is reverted back to the template.

Other considerations

  • If you are still having trouble, test the subnet filtering rules one at a time. After restarting the Mobility Print service, you should see the change immediately in the Mobility Print Admin interface.
  • If you want to use Subnet Filtering with BIND DNS servers, then there is a different method for setting up the DNS records that requires setting up Reverse Lookup Zones. If this sounds like your situation, let us know and we'll send you special instructions.