---
title: "W55RP20 Mac Address Rewrite"
url: "https://maker.wiznet.io/forum/15738"
markdown_url: "https://maker.wiznet.io/forum/15738/md"
type: "Forum topic"
category: "MCU & Boards"
author: "USASHIROU"
created: "2025-05-25T10:56:23+09:00"
last_activity: "2025-06-10T22:31:54+09:00"
language: "en"
tags: ["W55RP20"]
views: 10
replies: 4
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# W55RP20 Mac Address Rewrite

## Question

Asked by USASHIROU on 2025-05-25 in MCU & Boards.

I want to change the MAC address of my W55RP20.

There is a MAC Address writing guide, but I don't know how to rewrite it.https://docs.wiznet.io/Product/ioNIC/W55RP20/W55RP20-S2E/mac_address-write-guide-en

## Replies

### Reply 1 by USASHIROU, 2025-05-25

This explanation is for Write, and there is no explanation for ReWrite.

### Reply 2 by Alan, 2025-05-27

Have you previously uploaded the firmware to the W55RP20 and set the MAC address?
If so, you can simply erase the firmware completely and proceed again in the same way.

### Reply 3 by Lihan__, 2025-05-27

If a MAC address is already written in the W55RP20,
the only way to change it is to completely initialize all data stored in the internal Flash.

After initializing the Flash area, you can proceed with the steps mentioned in the link you previously provided.
**https://docs.wiznet.io/Product/ioNIC/W55RP20/W55RP20-S2E/mac_address-write-guide-en**

When entering a new MAC address,
please make sure that it does not duplicate the MAC address of any other device.

### Reply 4 by USASHIROU, 2025-06-10 (in reply to reply 2)

Thank you.
I was able to delete it.

[Meshtastic](https://meshtastic.org/docs/getting-started/flashing-firmware/nrf52/nrf52-erase/)

---

Source: https://maker.wiznet.io/forum/15738