@Ratsima 

Ratsima wrote

  @Alexandre. 

 

See this Wikipedia article: MAC Address which contains this:

 

Network nodes with multiple network interfaces, such as routers and multilayer switches, must have a unique MAC address for each NIC in the same network. However, two NICs connected to two different networks can share the same MAC address.

 

In other words, the Deco X20 should have three MAC addresses: one for the Wireless interface, one for the Wired LAN (Ethernet) interface and one for the WAN interface.

 

 

It depends how you interpret it. With my Deco M9 Plus, I can see at least three different MAC addresses:

MAC address #1: for WiFi 2.4GHz broadcasting

MAC address #2: for WiFi 5GHz broadcasting

MAC address #3: for wired connections

Just like Deco X20, Deco M9 Plus has two Ethernet ports. One would think each of them should have its own MAC address, but is it really necessary? Deco in Router mode uses autosensing to figure which port is WAN and which is LAN. This makes it two NICs connected to two different networks, WAN and LAN, right? One MAC address on both, formally not wrong according to what you found on WiKi.

When Deco is in AP mode, it has both Ethernet ports connected to the same network. Yet, if you think of these ports as a three-port switch, two ports of switch are external and third port is internal connected to internal NIC with MAC address, again with this concept one MAC address of a Deco unit should be enough.

These are my speculations. It will be fascinating to get overview of that topic from people who designed Deco, but these people don't seem to be participating in this forum.

I had an unused Deco X20 lying around. Here's the MAC address on the bottom of the device:

As you can see, the MAC address printed on the label is: b0:a7:b9:ae:38:54

I powered up the Deco and connected it to my existing router using a CAT5 cable; first on the top ethernet port and then on the bottom port. Then I scanned the LAN. Here are the results:

Top:     192.168.0.194      b0:a7:b9:ae:38:55      TP-Link Corporation Limited

Bottom:  192.168.0.194      b0:a7:b9:ae:38:55      TP-Link Corporation Limited

As you can see, the MAC address is one greater than the MAC address printed on the label. The MAC address is the same on either port.

  @Ratsima 

Looks like Deco MAC address is different when Deco is in Router mode than when it is in Access Point mode. I made a mistake assuming Deco mode makes no difference, so thanks for testing it with X20 and sharing the info. Learn something new about Deco every day.

So, in summary:

MAC address on the label is what Deco uses in Access Point mode. I have verified that with wired Deco M9 Plus and two wired M5s in my house.

For Deco in Router mode, Main Deco MAC address is based on the MAC address on the bottom label(=the last character of label MAC(hexadecimal)+1). Just like @David-TP  said in post #2.