--- title: "ASUS (RT, GT, and Merlin firmware) Configuration Guide" slug: "asus-rt-gt-and-merlin-firmware-configuration-guide" updated: 2026-03-03T19:05:07Z published: 2026-03-03T19:05:07Z canonical: "docs.ucstack.io/asus-rt-gt-and-merlin-firmware-configuration-guide" stale: true --- > ## Documentation Index > Fetch the complete documentation index at: https://docs.ucstack.io/llms.txt > Use this file to discover all available pages before exploring further. # ASUS (RT, GT, and Merlin firmware) Configuration Guide ## **Introduction** This guide provides our recommended configuration for ASUS routers (RT series, GT series, and Merlin firmware) to ensure optimal VoIP performance. --- ## **✅ Quick Checklist: Signs Your ASUS Router Needs VoIP Optimization** If you notice any of the following, this guide is for you : | **Symptom** | **Description** | | --- | --- | | **One-way audio** | You can hear the caller, but they can't hear you (or vice versa) | | **Phone disconnects after 15 minutes** | VoIP desk phone loses registration after ~15 minutes | | **Registration failures** | Phones won't register or stay registered | | **Dropped calls** | Calls drop after specific time periods | ## **✅ Compatible ASUS Models** | **Series** | **Popular Models** | **Notes** | | --- | --- | --- | | **RT Series** | RT-AC87U, RT-AC68U, RT-AC56U, RT-AC66U, RT-AC86U, RT-AX88U, RT-AX92U, RT-AX3000, RT-AX55, RT-AX52 | Most popular, Merlin firmware support | | **GT Series (ROG)** | GT-AXE16000, GT-AC5300, GT-AX11000 | Gaming series, same SIP ALG location | | **N Series (Older)** | RT-N56U, RT-N66U, RT-N15 | Some models have no SIP ALG | > [!NOTE] > **Note:** Some ASUS firmware versions (like 3.0.0.4.380.7378 on RT-N66U) have a bug where disabling SIP ALG stops all SIP traffic. Check your firmware version . ## **Provider-Specific Requirements** > [!WARNING] > **Important:** You need to configure the following settings on your ASUS router. | **Requirement** | **Specification** | | --- | --- | | **IP Range to Whitelist** | `64.26.133.64/27` | | **Ports to Open** | UDP `5060-5061` (SIP) and UDP `10000-20000` (RTP) | | **SIP Passthrough** | Must be **DISABLED** | --- ## **Core Configuration Steps** ### **1. Disable SIP Passthrough (CRITICAL)** > [!CAUTION] > **Critical:** SIP Passthrough (SIP ALG) is enabled by default on ASUS routers and MUST be disabled for proper VoIP operation . | **Web Interface Method** | Log in to router | `http://192.168.1.1` or `http://192.168.50.1` | | --- | --- | --- | | Go to **Advanced Settings** | Click **WAN** in the left menu | | Click **NAT Passthrough** | Tab at the top of the WAN page | | Disable SIP Passthrough | Change **SIP Passthrough** to **Disable** | | Apply settings | Click **Apply** and reboot router | | **SSH/Telnet Method** | Connect via SSH | Use a terminal client (PuTTY, Terminal) | | Check current value | `nvram get nf_sip` (should return "1") | | Disable SIP ALG | `nvram set nf_sip=0` then `nvram commit` | ### **2. Port Forwarding for VoIP** Port forwarding must be enabled in the WAN configuration. The port range used by your VoIP phone must be assigned to its local IP address . | **Navigation** | **Setting** | **Value** | | --- | --- | --- | | `WAN > Virtual Server / Port Forwarding` | **Service Name** | VoIP-SIP | | **Protocol** | UDP | | **External Port** | `5060-5061` and `10000-20000` | | **Internal Port** | Same as external | | **Internal IP** | Your VoIP device's IP address | ### **3. IPTV/VoIP Configuration** ASUS routers have a dedicated IPTV section for VoIP configuration . | **Navigation** | **Setting** | **Action** | | --- | --- | --- | | `Advanced Settings > IPTV` | Configure VoIP | Select ISP profile or manual settings | | UDP Proxy | Configure if required by your ISP | ### **4. QoS for VoIP Priority** ASUS routers have built-in QoS to prioritize VoIP traffic . | **Navigation** | **Setting** | **Action** | | --- | --- | --- | | `Adaptive QoS > Bandwidth Management` | Set VoIP priority | Click **VOIP/Video Streaming** to set highest priority | | Apply settings | Click **Finish and Apply** | ### **5. Important Model Notes** | **Model** | **Important Note** | | --- | --- | | **RT-N56U** | No firewall masking SIP packets; works without interference. No SIP ALG to disable . | | **RT-N66U** | Firmware 3.0.0.4.380.7378 has bug where disabling SIP ALG stops all SIP traffic. With latest firmware, leave SIP ALG enabled . | | **GT-AXE16000** | Some users find no need to disable SIP ALG on newer routers; NAT Helper may be sufficient . | --- ## **IP Whitelist Configuration** Create a port forwarding rule to allow traffic from our servers to reach your VoIP device. | **Field** | **Value** | | --- | --- | | **Service Name** | `VoIP-Provider` | | **Source IP** | `64.26.133.64/27` | | **Destination IP** | Your VoIP device's IP address | | **Port Range** | `5060-5061` and `10000-20000` | | **Protocol** | UDP | > [!TIP] > **Note:** The `/27` notation includes **32 IP addresses** ranging from `64.26.133.64` to `64.26.133.95`. --- ## **✅ Configuration Checklist** | **#** | **Task** | | --- | --- | | 1 | **SIP Passthrough disabled** in WAN > NAT Passthrough | | 2 | **Port forwarding** configured for VoIP device IP | | 3 | **QoS enabled** with VoIP priority | | 4 | **Whitelist rule created** for `64.26.133.64/27` | | 5 | **Firmware checked** for known bugs (RT-N66U specific) | | 6 | **Test call successful** with two-way audio | --- ## **Verification & Testing** ### **SIP-ALG Verification Test** > [!NOTE] > **Test URL:** `http://mcstest.visualware.com/myspeed/myvoiph5_g711_sipalg.html` | **Item** | **Detail** | | --- | --- | | **Requirement** | Download the BCS utility when prompted | | **Expected Result** | `SIP ALG Firewall: N` | ### **Functional Testing** | **Test Case** | **Procedure** | **Expected Result** | | --- | --- | --- | | **Outbound Call** | Place call to external number | Two-way audio established | | **Inbound Call** | Call in from external number | Phone rings, call connects with two-way audio | | **Stability Test** | Monitor for 15+ minutes | Phone stays registered, no disconnects | ## **🚨 Troubleshooting** | **Issue** | **Likely Cause** | **Solution** | | --- | --- | --- | | **One-way audio** | SIP Passthrough still enabled | Disable in WAN > NAT Passthrough or via SSH | | **Phone disconnects after ~15 minutes** | SIP ALG interference | Disable SIP Passthrough and verify with SSH | | **No SIP traffic after disabling ALG** | Firmware bug (RT-N66U) | Update firmware or leave SIP ALG enabled | | **Port forwarding not working** | IP address changed | Use DHCP reservation for VoIP device | --- ## **🛠️ Official ASUS Tutorials** For visual guidance on configuring your ASUS router, visit the official ASUS support page: 🔗 [**ASUS Support**](https://www.asus.com/support/)