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How to Resolve a LAN-WAN IP Conflict

Written by Sunny

Purpose

This document explains how to identify and resolve a LAN-WAN IP conflict on a Pronto router.

What is a LAN-WAN IP Conflict?

A LAN-WAN IP conflict occurs when the router's LAN network and WAN network belong to the same IP subnet.

Example:

Interface

IP Address

WAN

192.168.0.100

LAN

192.168.0.1/24

Since both interfaces are using the 192.168.0.0/24 network, the router cannot properly distinguish between internal and external traffic.

This may result in:

  • Internet connectivity issues

  • Routing problems

  • Devices being unable to reach external resources

  • LAN/WAN IP Conflict alerts

Symptoms

You may observe one or more of the following:

  • LAN/WAN IP Conflict Detected alert

  • Clients connected to the LAN cannot access the internet

  • Intermittent connectivity issues

  • Routing instability

  • WAN receives an IP address, but internet access is unavailable

Common Causes

ISP Modem Uses the Same Network as LAN

Example:

  • ISP modem gateway: 192.168.0.1

  • Pronto LAN subnet: 192.168.0.0/24

This is the most common cause.

Router Connected Behind Another Router

When the upstream router and Pronto LAN use the same subnet, a conflict occurs.

Incorrect Static WAN Configuration

A manually configured WAN IP may overlap with the LAN subnet.

Resolution Method 1: Change the LAN Subnet (Recommended)

Step 1

Navigate to:

Configure → Network → LAN

Step 2

Modify the LAN IP range to a different subnet.

Example:

Current:

  • LAN IP: 192.168.0.1

  • Subnet: 255.255.255.0

Change to:

  • LAN IP: 192.168.10.1

  • Subnet: 255.255.255.0

Step 3

Save the configuration.

Step 4

Allow connected devices to obtain new IP addresses from the updated DHCP scope.

Resolution Method 2: Modify the Upstream Network

If you manage the upstream modem or router:

  1. Log in to the upstream device.

  2. Change its LAN subnet to a different network.

  3. Reconnect the Pronto router.

Example:

Change upstream network from:

  • 192.168.0.0/24

To:

  • 192.168.100.0/24

Resolution Method 3: Verify Static WAN Settings

If the WAN interface is configured with a static IP:

  1. Navigate to WAN/Uplink Configuration.

  2. Verify the configured IP address and subnet.

  3. Ensure the WAN subnet does not overlap with the LAN subnet.

Example:

Valid:

  • WAN: 10.10.10.2/24

  • LAN: 192.168.1.1/24

Invalid:

  • WAN: 192.168.1.2/24

  • LAN: 192.168.1.1/24

Verification

After applying the changes:

  1. Confirm the LAN and WAN interfaces use different subnets.

  2. Verify clients receive valid DHCP addresses.

  3. Test internet access from a connected client.

  4. Confirm the LAN/WAN IP Conflict alert has cleared.

  5. Verify the router reports online status in the Cloud dashboard.

Best Practices

  • Use different IP ranges for LAN and WAN interfaces.

  • Avoid using the same subnet on multiple routers.

  • Verify subnet assignments before deploying new equipment.

  • When deploying behind an ISP modem, check the modem's LAN network before configuring the router.

Using unique subnets helps prevent routing conflicts and simplifies network management.

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