NBN VoIP Compatibility for Australian Businesses

NBN Technology Types and VoIP: The Summary

FTTP: The Best NBN Connection for VoIP

FTTP (Fibre to the Premises) delivers optical fibre directly to your building. Because there is no copper component in the connection, FTTP provides consistent, low-latency performance regardless of distance or time of day. Latency is typically 2-5ms with minimal jitter. For a business that relies heavily on VoIP and cannot tolerate call quality variation, FTTP is the preferred connection type.

If FTTP is available at your address but the building is not yet connected (common in new developments or recently upgraded areas), contact your NBN retailer. FTTP upgrade programs have expanded significantly since 2022 and many formerly FTTN premises can now access FTTP connections.

FTTN connections (fibre to a street cabinet, then copper wire to your premises) are the most common source of VOIP call quality problems in Australia. If your NBN is FTTN and your copper run is long or in poor condition, call quality will be inconsistent regardless of your plan speed. The fix is either an upgrade to FTTC or FTTP (which you can request from NBN Co) or a 4G failover connection to avoid the copper run on critical calls.

A lot of businesses assume poor VOIP call quality means their internet plan is too slow. Speed is rarely the issue. A voice call uses only about 100Kbps of bandwidth. The actual causes are latency (the delay between sending and receiving packets), jitter (inconsistency in that delay), and packet loss. An FTTN connection with 50Mbps download but high jitter will have worse phone call performance than an FTTC connection with 25Mbps but low jitter.

FTTC: Excellent Performance, Close to FTTP

FTTC (Fibre to the Curb) is one of the newer NBN deployments across Australia. Fibre runs to a distribution point (DP) unit in a pit directly outside or near your premises, typically within 10 to 30 metres. A short VDSL2 copper run bridges the final distance from the DP to your building's existing copper socket.

Because the copper component is extremely short, FTTC performance is substantially better than FTTN and approaches FTTP in practice. Latency is typically 3-8ms and jitter is low. Businesses on FTTC can run multiple simultaneous VoIP calls without concern about the connection technology itself. The limiting factors shift to router configuration, SIP ALG handling, and internal network setup, not the NBN connection.

FTTB: Common in Multi-Tenancy Commercial Buildings

FTTB (Fibre to the Building) is the dominant NBN technology for businesses in multi-tenancy office buildings, commercial towers, and mixed-use developments. Fibre runs to the building's main distribution frame (MDF), typically in the basement communications room, and from there the existing internal building copper serves each tenancy.

Internal copper runs in commercial buildings are typically under 100 metres and are in better condition than the street copper used by FTTN. FTTB latency is generally 5-10ms and is reliable for VoIP. The main risk factor is aging internal building copper in older commercial properties. If your business is in an older building and experiencing VoIP quality issues, check with the building manager whether the internal copper has been tested. Old or poorly jointed internal copper can produce the same symptoms as FTTN, variable latency and occasional packet loss, even though the external connection is fibre-based.

HFC: Generally Reliable With One Caveat

HFC (Hybrid Fibre Coaxial) uses the old Foxtel cable TV infrastructure, coaxial cable, for the final connection to your premises. HFC is generally reliable for business VoIP. Latency is typically 5-15ms, which is well within acceptable range for voice.

The caveat is that the coaxial network is shared between nearby premises. In residential-dense areas, peak-hour congestion can occasionally affect latency. During business hours this is typically not a problem. If you notice VoIP quality degrading in the late afternoon or evening, peak-hour coaxial congestion is the likely cause. A business-grade NBN plan (with dedicated CVC allocation) from your retailer can help, as some providers prioritise business plan traffic during congestion events.

FTTN: The Most Problematic NBN Type for VoIP

FTTN (Fibre to the Node) is the NBN technology that causes the most VoIP problems for Australian businesses. The fibre component runs to a street cabinet (node), and from there a copper telephone line runs to your premises. The length and condition of that copper run determines your line's latency and stability.

Copper runs under 300 metres typically perform well enough for VoIP. Copper runs over 600 metres begin to show variable latency. Deteriorated copper, aged joints, water-damaged pits, and corroded connections can cause significant quality issues regardless of distance. If your business is on FTTN and experiencing VoIP problems, request a line quality check from your NBN retailer and ask specifically about latency and jitter, not just download speed.

Fixed Wireless: Workable for Small Deployments

Fixed Wireless NBN is deployed in regional and rural areas where fibre is not economically viable. The connection uses radio signals from a nearby tower to an antenna mounted on your roof. Latency is typically 30-60ms, higher than any fibre-based NBN type but generally workable for VoIP.

For businesses in Fixed Wireless areas running 1-3 simultaneous calls, cloud phone system generally works. Variability comes from weather interference, tower congestion, and distance to the tower. Businesses planning to run 5+ simultaneous calls on Fixed Wireless should test under real load conditions before committing to a full deployment.

Satellite Internet and VoIP: Sky Muster vs Starlink

There are two satellite internet options available in rural Australia, and they have completely different implications for VoIP. Most VoIP guidance about satellite refers to the older Sky Muster system, but Starlink has changed the picture significantly for rural businesses.

Sky Muster: Not Compatible With Real-Time VoIP

Sky Muster is NBN Co's geostationary satellite service for very remote areas. Geostationary satellites orbit approximately 35,000km above the earth. The signal must travel up to the satellite and back twice for every packet, adding a minimum round-trip latency of 600 milliseconds. Real-time VoIP requires latency below 150ms for acceptable quality. Sky Muster is fundamentally incompatible with standard SIP-based VoIP.

Businesses on Sky Muster who need telephone service should use a mobile-based solution, a hosted business number that rings through to a mobile app, rather than attempting to deploy SIP desk phones.

Starlink: VoIP-Capable With Caveats

Starlink (SpaceX) uses low-earth-orbit satellites at approximately 550km altitude. Because the satellites are far closer to earth than geostationary systems, Starlink latency is typically 20-60ms, well within VoIP-compatible range. Many Australian rural businesses now run VoIP successfully over Starlink.

Two caveats to be aware of: First, Starlink uses CGNAT (Carrier Grade NAT), which means you do not have a dedicated public IP address. Most current Australian cloud phone system companies handle CGNAT correctly, but confirm with your provider before deploying. Second, Starlink occasionally experiences brief dropouts during satellite handoffs (when your terminal switches between overhead satellites). These dropouts are typically under one second and are not a problem for most VoIP use cases, but are worth knowing about for high-volume environments.

How Many Simultaneous Calls Can Your NBN Support?

Each simultaneous VoIP call uses approximately 80-100 kbps of bandwidth (G.711 codec, the standard for Australian VoIP deployments). On an NBN25 plan (25 Mbps download / 10 Mbps upload), you have theoretical bandwidth for roughly 100 simultaneous calls.

Bandwidth is almost never the bottleneck for VoIP on NBN. The real constraints are latency, jitter, and packet loss, all determined by your NBN connection technology type, not your plan speed. Upgrading from NBN25 to NBN100 will not fix VoIP problems caused by FTTN copper degradation. Switching from FTTN to FTTP on an NBN25 plan will almost always outperform FTTN on NBN100 for voice quality.

The practical recommendation for most Australian small businesses: run NBN50 or above not because you need the bandwidth for calls, but because higher-tier plans typically come with greater CVC (Connectivity Virtual Circuit) allocation from your retailer, reducing peak-hour congestion. For offices with 10 or more staff regularly making calls, a dedicated business-grade NBN plan provides service level commitments and prioritised fault resolution that residential plans do not include.

SIP ALG: The Number One Cause of NBN VoIP Failures in Australia

Across every NBN connection type, one router setting causes more VoIP registration failures and call quality problems than any other: SIP ALG.

SIP ALG (Session Initiation Protocol Application Layer Gateway) is a feature built into most consumer and SMB routers. It was designed to help SIP traffic pass through NAT more reliably. In practice, most SIP ALG implementations incorrectly modify SIP packet headers as they pass through the router. The result is corrupted SIP signalling that causes phones to fail to register, produces one-way audio (one party can hear the other but not vice versa), drops calls after 30-60 seconds, or prevents inbound calls from ringing at all.

To disable SIP ALG: log into your router's admin interface (typically 192.168.0.1 or 192.168.1.1 in a browser). Look under Advanced Settings, NAT, ALG, or Firewall. The setting may be labelled 'SIP ALG', 'SIP Passthrough', 'SIP Transformations', or 'VoIP ALG'. Disable it, save, and restart the router. For step-by-step instructions by Australian router brand, see our guide to QoS and SIP settings on Australian routers.

Other Steps to Optimise VoIP on Any NBN Connection

Enable QoS for Voice Traffic

QoS (Quality of Service) tells your router to prioritise VoIP packets over other internet traffic. This prevents video streaming, large file downloads, or background updates from degrading call quality during busy periods. Set UDP port 5060 (SIP signalling) and UDP ports 10000-20000 (RTP audio) to high priority. DSCP marking, setting voice packets to EF (Expedited Forwarding, DSCP 46), achieves the same on networks with managed switches.

Use Wired Ethernet for IP Phones

Every IP desk phone should be connected via wired Ethernet, not Wi-Fi. Wi-Fi introduces variable latency and occasional packet loss as devices compete for airtime. On a wired connection, each device has a dedicated full-duplex channel to the switch. For reception desks, primary business lines, or any phone where reliability matters, Wi-Fi is not appropriate. For hot-desk phones where cabling is impractical, Wi-Fi is a compromise, acceptable for occasional use, not for a primary business line.

Consider a Business-Grade Router

The modem-router supplied by most NBN retailers is designed for residential internet, not multi-phone business VoIP. For businesses deploying three or more IP phones, a dedicated business router provides more reliable SIP handling, proper QoS, and better NAT traversal. The Draytek Vigor series is widely used in Australian VoIP deployments for its well-regarded SIP support. Ubiquiti EdgeRouter and MikroTik are popular among technically capable businesses. Budget $300-600 for a purpose-built business router, it is often the highest-value single hardware change for VoIP reliability.

Use G.711 Codec, Not G.729

G.729 is a compressed voice codec that reduces call bandwidth from ~100kbps to ~8kbps. It is sometimes configured by providers or resellers as a bandwidth-saving measure. On any NBN connection above the minimum tier, this is an unnecessary trade-off, bandwidth is not the VoIP constraint on NBN, and G.729 compression introduces audio artefacts and slightly higher processing latency. Use G.711 (PCMU or PCMA) for the best quality on any NBN connection above NBN12.

The PSTN Copper Shutdown

Australia's PSTN copper telephone network has been progressively decommissioned as NBN rollout has completed. When NBN is available at a premises, traditional voice services on the copper network are transitioned to VoIP or ceased. If your business has not yet moved to a proper VoIP service and is still on an ISP-supplied ATA (the green phone port on your NBN modem), see our ATA adapter guide and VoIP vs traditional phone comparison to understand your migration path.

If you have purchased a new IP desk phone and want to understand what to do next, our new IP phone setup guide covers business phone company selection, SIP credential entry, Ethernet connection, and getting the phone registered for the first time.

Does NBN Type Affect Phone System Cost?

NBN connection type does not change the cost of a cloud phone plan — plans run $20-35 per user per month (inc. GST) regardless of whether you are on FTTP, FTTC, FTTN, or HFC. What changes by NBN type is call quality and whether you need a QoS-capable router to prioritise voice traffic. A QoS router costs $100-300 as a one-off if your current router does not support it. FTTN and FTTC connections sometimes benefit from QoS configuration. FTTP and cable connections typically do not need it.

Once you have confirmed your NBN connection type is compatible with cloud phone calls, the next step is configuration. Our guide to setting up business phones on the NBN covers the full setup process including NBN-specific QoS settings, router requirements for each technology type, and the most common issues by connection type.

NBN connection type is one of the biggest factors in whether VoIP will work reliably for your business. If you have an NBN connection type known for reliability problems, or if your business has very specific uptime requirements, our guide to when VoIP is not the right choice for your business covers the scenarios where you need additional planning before committing to a full VoIP setup.

How do I find out which NBN technology type is at my address?

Use the address checker at nbnco.com.au. Enter your business address and the result will show your current NBN technology type and any upgrade plans. Your NBN retailer's account portal also typically shows your connection technology. Ask specifically for the technology type, FTTP, FTTC, FTTB, FTTN, HFC, or Fixed Wireless, not just your speed tier.

Can I upgrade from FTTN to FTTP for better VoIP quality?

In many cases, yes. NBN Co has an ongoing program upgrading FTTN connections to FTTP in areas where the copper network requires significant maintenance. If your area is included, you can request the upgrade through your NBN retailer. The upgrade is typically free, though it may require an NBN technician visit. Check nbnco.com.au for current availability at your address.

My NBN speed test results are good but VoIP quality is poor. Why?

Speed tests measure download and upload throughput, not latency or jitter, which are what VoIP depends on. Before investigating anything else, disable SIP ALG on your router. It is the most common cause of this symptom on any NBN connection type. If that does not resolve the issue, run a ping test to measure round-trip latency and jitter. Latency above 80ms or jitter above 30ms will cause noticeable voice degradation even on a fast connection.

Does my NBN plan speed affect VoIP quality?

Rarely. Each VoIP call uses approximately 80-100 kbps. Even an NBN25 plan has more than enough bandwidth for multiple simultaneous calls. Upgrading to NBN100 will not improve call quality unless your connection was genuinely bandwidth-saturated. Connection technology type and router configuration matter far more than plan speed.

Does Starlink support VoIP for Australian businesses?

Yes, with caveats. Starlink's LEO network delivers 20-60ms latency, which is sufficient for SIP-based VoIP. Most Australian small businesses running 1-5 simultaneous calls over Starlink report acceptable quality. The main consideration is CGNAT, Starlink does not provide a dedicated public IP address. Most current Australian cloud phone system companies handle this correctly, but confirm before deploying. Do not confuse Starlink with Sky Muster (NBN Co's geostationary satellite): Sky Muster has 600ms+ latency and is not compatible with real-time VoIP.

What is SIP ALG and why does it break VoIP?

SIP ALG (Application Layer Gateway) is a router feature that attempts to modify SIP traffic passing through NAT. Most implementations do this incorrectly, corrupting SIP headers in ways that prevent phones from registering, cause one-way audio, or drop calls after 30-60 seconds. It is enabled by default on almost all Australian NBN routers. Disabling it is the first step recommended by every major Australian business phone company. Find it under Advanced, NAT, ALG, or Firewall settings in your router's admin interface.

What router should I use for VoIP on NBN?

The consumer modem-router supplied by your NBN retailer is sufficient for basic setups once SIP ALG is disabled. For businesses with 3+ IP phones, a dedicated business router improves reliability significantly. The Draytek Vigor series is widely used in Australian VoIP deployments and has well-regarded SIP handling. Ubiquiti EdgeRouter and MikroTik are popular options for technically capable users. Budget $300-600 for a purpose-built business router, it is often the highest-value single hardware change for VoIP stability.

My new IP phone shows 'Not Registered', is this an NBN problem?

Usually not. 'Not Registered' typically means the phone has no SIP credentials configured, or that SIP ALG on the router is blocking registration. First, confirm you have a business phone company account and have entered SIP credentials into the phone. If credentials are correct but the phone still will not register, disable SIP ALG on your router. Our new IP phone setup guide covers the full process and troubleshooting checklist.

Not sure what NBN connection type your business has or whether it's causing your phone problems? Tell us your suburb and ISP and we'll tell you what connection type you're likely on and what to do about it. We reply personally, usually within one business day.