Openwrt on Netgear R6220 with mwan3... Second WAN and LAN have same Mac Address

[Audioctor]

Hello, I recently installed Openwrt on my Netgear R6220 Router. I intend to use it with multiple WAN connections with Load Balancing/Fail over using mwan3.
After installation, I was successful in configuring 2 of the LAN ports into WANB and WANC ports as per the procedure mentioned in user guide.

I have connected my ISP modems (all from different providers) to the 3 WAN ports.
All the ports successfully acquire the respective IP addresses from the modems

I am able to access the Internet when the Primary WAN port is Live. While when the primary WAN is off, I cannot access the internet or ping openwrt.org through either WANB or WANC. Though, I am able to access the Web UI of the respective modems.

On having a closer look I have discovered that my LAN as well as WANB and WANC interfaces have the same Mac address. I believe this is probably causing the problem.

Please help me get around this.

Thanks

[vgaetera]

You can try to change MAC address, or utilize virtual interfaces.

[Audioctor]

Thanks.
I tried changing the Mac address using the Mac Address override option. It won't accept any random Mac address that I enter. So what other Mac address can I use besides the default one?
I am an absolute novice at this. So explain in the fundamental layman terms to me. Please guide with options using the Luci web UI. I am not comfortable in handling the command line.

Thanks again.

[vgaetera]

Specify the new MAC address by incrementing the last bit of the old one.

Unfortunately, web interface sometimes fails:
MAC override does not work - #5 by wulfy23

[Audioctor]

Thanks a lot @vgaetera for your quick help. It worked. All my WAN ports are working now.
Shall be getting into load balance configurations now. Will get back when I need more help.
Thanks again.