The Security Gatekeeper Behind Reliable Printing and Scanning

A firewall is a security system that monitors network traffic and decides whether a connection should be allowed, blocked, or restricted. For printing and scanning, it often determines whether a computer can find a printer, send a print job, open a device’s web page, or receive a scanned file. A firewall is not inherently a printing problem; it is a policy enforcement point. When its rules do not match the way a printer, scanner, computer, or network is configured, ordinary tasks can stop working.

What a firewall does

Networks exchange information in small units of traffic between devices. A firewall evaluates that traffic against rules based on details such as source and destination IP addresses, port numbers, protocols, connection direction, user or application identity, and network profile. If no rule permits the traffic, a default-deny policy may block it.

Firewalls can be software running on a computer or hardware and software operating at the network edge. Most organizations use more than one layer. A Windows or macOS computer may have a host firewall, while the router, security appliance, or managed switch environment enforces broader network controls.

A firewall should not be treated as an obstacle to remove. It is a control to configure precisely: permit the required service, from the required devices, on the required network, and block everything else.

For a local USB printer, firewall settings usually have little relevance because the print data does not cross the network. For Ethernet, Wi-Fi, and multifunction devices, firewall configuration can be essential.

Why printers and scanners are affected

Modern multifunction printers are small networked computers. They may offer printing, scanning, device discovery, status monitoring, email delivery, cloud access, firmware updates, and browser-based administration. Each feature can use a different protocol and connection direction.

For example, a computer may send a job to a printer over Internet Printing Protocol (IPP), while the printer reports toner status using SNMP. Scan-to-computer commonly requires the receiving computer to accept an inbound connection or to run a vendor service that listens for one. If the workstation firewall allows printing outbound but blocks the scanner’s inbound session, printing can work while scanning fails.

Common symptoms of a blocked rule

• The printer appears offline even though it is powered on and connected.
• Printing works by IP address but the device cannot be discovered automatically.
• A scan begins at the device but never arrives at the selected computer or shared folder.
• The printer’s embedded web server cannot be opened from a browser.
• Only users on a guest Wi-Fi network, VPN, or a particular office segment experience failures.
• Status tools show no ink, toner, paper, or error information.

Firewall types in a printing environment

Understanding where filtering occurs makes troubleshooting much faster. A job may pass through several controls: the sender’s host firewall, a wireless access point policy, an internal firewall between network segments, and the device’s own security settings.

Protocols and ports: use the device documentation

Ports identify network services. They are useful when creating a rule, but a universal “open these ports” approach is unsafe because models, operating systems, drivers, and scan destinations differ. Consult the device manufacturer’s current network guide and the organization’s security policy before changing rules.

Common examples include IPP for printing, often associated with TCP port 631; RAW or JetDirect printing, commonly TCP port 9100; and LPR/LPD, commonly TCP port 515. SNMP may be used for discovery and monitoring, while multicast DNS or other discovery methods can help computers locate devices automatically. Scan-to-folder may use SMB, scan-to-email may use SMTP, and scan-to-computer tools may rely on vendor-specific services.

Prefer direct, authenticated services

Where supported, use encrypted and authenticated options such as IPPS rather than unencrypted printing. Do not expose printer administration interfaces or print ports directly to the public internet. Remote users should normally connect through an approved VPN or managed print service, not through port forwarding on a home or office router.

A safe way to troubleshoot firewall-related failures

Do not begin by disabling every firewall. That can hide the real cause and leave computers exposed. Instead, test a specific path and make the smallest change that resolves it.

1. Confirm the device address and network. Print or view the network configuration page and note the IP address, subnet, Wi-Fi or Ethernet status, and hostname.
2. Test basic reachability. From an authorized computer on the same intended network, test whether the device’s web interface or a documented service is reachable. A failed ping alone is not conclusive because many devices ignore ICMP.
3. Identify the exact task that fails. Separate printing, discovery, status monitoring, scan-to-computer, scan-to-folder, and web administration. They may use different traffic flows.
4. Check the network profile and logs. On managed systems, confirm whether the connection is marked Private, Public, or Domain as appropriate. Review firewall or endpoint-security logs for dropped traffic.
5. Create a narrow allow rule. Limit it to the printer’s fixed IP address or approved subnet, the needed protocol or application, and the intended profile or network zone.
6. Retest and document. Verify the feature from a normal user account, record the rule’s purpose, and remove temporary test exceptions.

If a device works only intermittently, address changes are a frequent cause. Reserve the printer’s address through DHCP or assign a properly managed static address outside the dynamic range. A firewall rule tied to an old address will look like a random printing failure after a lease change.

Practical configuration guidance

For a home office, place the computer and printer on the trusted local network rather than a guest network. Guest networks often isolate clients from one another by design. In Windows, allow the approved printer application or relevant sharing and discovery features only on the Private network profile; avoid broad allowances on Public networks.

For a business, separate printers and multifunction devices into a managed printer or IoT VLAN when practical. Then permit only necessary flows from employee devices, print servers, and management systems. Restrict browser-based administration to IT administration workstations, and use a print server or centrally managed deployment where it improves auditing and driver control.

• Change default administrator passwords on every networked printer.
• Install manufacturer firmware updates through a controlled maintenance process.
• Disable unused protocols, legacy print services, Wi-Fi Direct, or cloud functions.
• Use secure scan destinations with least-privilege credentials.
• Review printer address books and stored scan credentials regularly.
• Back up configuration settings before major network changes.

When the issue is not the firewall

Similar symptoms can come from weak Wi-Fi, expired credentials for a shared folder or email server, incorrect DNS, incompatible drivers, print spooler errors, certificate problems, or network isolation settings. A printer may also reject traffic because its own access-control list, TLS configuration, or administrator policy is stricter than expected.

Start with the simplest facts: is the device connected, does it have the expected address, can an authorized computer reach it, and does the selected protocol match the installed driver and device configuration? This sequence avoids unnecessary rule changes and keeps the security boundary intact.

References

• National Institute of Standards and Technology (NIST)
• Cybersecurity and Infrastructure Security Agency (CISA)
• RFC Editor
• Microsoft Support