---
title: "How to resolve IP conflict when using multiple Wiznet devices with ConfigTool?"
url: "https://maker.wiznet.io/forum/15843"
markdown_url: "https://maker.wiznet.io/forum/15843/md"
type: "Forum topic"
category: "Serial-to-Ethernet & ConfigTool"
author: "sopelos"
created: "2025-08-18T17:00:07+09:00"
last_activity: "2025-08-19T13:54:45+09:00"
language: "en"
views: 7
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# How to resolve IP conflict when using multiple Wiznet devices with ConfigTool?

## Question

Asked by sopelos on 2025-08-18 in Serial-to-Ethernet & ConfigTool.

Hello

I am working on a project that uses several Wiznet modules on the same local network & I noticed that when I scan them with ConfigTool; sometimes two devices show up with the same IP address. This creates problems because I can not reliably connect to the right device and occasionally one device becomes unreachable.

I tried manually reassigning IP addresses through ConfigTool but after a reboot, one of the devices sometimes reverts to the old conflicting IP.

I also checked my DHCP server and it looks like static/manual assignments from ConfigTool do not always sync properly with what the router is giving out.

This is making it difficult to maintain a stable network setup. Checked <https://docs.wiznet.io/Product/ioNIC/W55RP20/W55RP20-S2E/Config-tool-Guide-en> guide for reference. While searching for solutions; I noticed many tutorials explain basics step by step, similar to guides on [how to use ChatGPT](https://www.igmguru.com/blog/how-to-use-chatgpt), which makes me think a clear workflow for avoiding IP conflicts would also help beginners.

Is there a recommended way to prevent or fix IP conflicts when managing multiple devices with ConfigTool?

Should I always disable DHCP and set everything manually is there a best practice for combining ConfigTool with router DHCP reservations?

Any advice / examples would be greatly appreciated.

Thank you !!

## Replies

### Reply 1 by Lihan__, 2025-08-19

To resolve this issue, we recommend **disabling DHCP and operating in Static IP mode**.

As you mentioned, if the IP address changes back after a reset, this is most likely because the device is currently operating in **DHCP mode**.

Please also check whether the two modules have the **same MAC address**. If they are running in DHCP mode with identical MAC addresses, the DHCP server may recognize them as the same device, which could cause an IP conflict. (Although this case is rare, it is worth verifying.)

While receiving IPs correctly from the DHCP server may reduce such issues, the most reliable method is to use **Static IP mode with fixed addresses**.

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Source: https://maker.wiznet.io/forum/15843