VLANs, Firewalls, and More: A Guide to VoIP Network Security for SMBs
How SMBs Can Use VLANs, Firewalls, and Best Practices to Improve VoIP Performance
In today’s fast-paced business environment, reliable communication is more essential than ever. Many small businesses are turning to hosted VoIP solutions like those offered by FluentStream to streamline operations and save costs.
Properly managing your network infrastructure plays a critical role in VoIP performance. In this guide, we’ll walk you through how VLANs, firewalls, and best practices can help your business get the most from your VoIP system without disruption or delays.
Why VoIP Quality Can Suffer Without the Right Setup
VoIP transmits voice data over the internet, which means it shares bandwidth with every other device on your network including printers, computers, streaming devices, and more. Without a well-structured network, your phone calls can suffer from:
- Choppy or robotic audio
- Dropped calls
- VoIP registration issues
- Security vulnerabilities
That’s where smart network design comes in.
VLANs: Prioritize Voice Traffic
Virtual Local Area Networks (VLANs) are one of the most effective tools for improving VoIP performance. A VLAN logically separates network traffic, allowing voice data to flow separately from regular internet traffic.
Why VLANs Matter for VoIP
- Prioritization: VoIP data can be prioritized using Quality of Service (QoS) policies, ensuring call packets are delivered first.
- Isolation: Phones on a separate VLAN are isolated from data traffic, improving security and reducing interference.
- Scalability: As your business grows, VLANs make it easier to manage increasing numbers of phones and devices.
How to Set Up a VLAN for VoIP
- Enable VLAN support on your switch and router (check that your hardware supports 802.1Q).
- Create a dedicated VLAN, e.g., VLAN 20 for voice.
- Assign VoIP phones to that VLAN, either manually or via LLDP-MED or DHCP option 132.
- Configure QoS policies to prioritize UDP traffic on SIP and RTP ports (typically 5060 and 10000-20000 UDP).
💡 Tip: FluentStream’s support team can assist you in planning VLAN deployments if needed.
Firewalls: Secure Your Phone System Without Blocking It
Firewalls are essential for network security, but misconfigurations can wreak havoc on VoIP systems. Too often, phones can’t register, calls fail to connect, or one-way audio occurs due to blocked ports or SIP ALG issues.
VoIP-Friendly Firewall Best Practices
- Disable SIP ALG: Many consumer-grade routers have SIP Application Layer Gateway (ALG) enabled by default, which often causes more problems than it solves. Disable it to allow SIP traffic to pass correctly.
- Open the Correct Ports:
- SIP Signaling: UDP/TCP 5060 (and sometimes 5061 for TLS)
- RTP Media: UDP 10000–20000
- Provisioning: Typically HTTP/HTTPS on 80/443 or vendor-specific ports
- Use Static IPs or DHCP Reservations for VoIP phones to simplify troubleshooting and traffic rules.
- Whitelist FluentStream's IP ranges in your firewall to ensure uninterrupted service. (FluentStream provides these IPs in their documentation.)
VoIP Network Best Practices
Even if you're not an IT expert, these straightforward tips can dramatically improve your VoIP quality and reliability.
1. Separate Voice and Data Traffic
Use VLANs to avoid bandwidth competition between calls and other devices. Never run your entire office network on a single flat LAN.
2. Implement Quality of Service (QoS)
Configure QoS on your router to prioritize VoIP traffic based on DSCP values (often EF 46 for voice).
3. Use Wired Connections Where Possible
VoIP calls over Wi-Fi can be unreliable. Hardwire desk phones with Ethernet cables for optimal performance.
4. Avoid Double NAT
If you have multiple routers or firewalls, you might unintentionally create a double NAT scenario. This causes VoIP registration issues and call drops. Ensure only one device is performing NAT.
5. Monitor Network Usage
Use simple monitoring tools to track bandwidth usage. If your internet connection is saturated (especially uploads), voice quality will degrade. Consider business-grade internet with sufficient upload speeds.
6. Keep Firmware Updated
Outdated firmware on routers, switches, or phones can lead to incompatibility or security holes. Regular updates help keep everything stable and secure.
VoIP Doesn’t Have to Be Complicated
When set up properly, hosted VoIP services like FluentStream can deliver high-quality, secure, and scalable communication for businesses of all sizes. With a bit of smart network design, including VLAN segmentation, firewall tuning, and QoS, you can ensure your calls are crystal-clear and your system is protected.
Need Help?
If you're unsure about VLANs or firewall settings, FluentStream’s support team can work with your IT provider or directly assist you in configuring your network for optimal performance. Whether you’re starting from scratch or troubleshooting existing issues, it pays to get your network VoIP-ready.
Want to learn more about VoIP readiness or need network guidance? Contact FluentStream Support or check out our VoIP Network Configuration Guide.
