Can't get DHCP IP on WAN LAN1 interface

[Silem2013]

I have a weird issue - I have 2 ISPs that I want to use for failover.  I set WAN and LAN1 interfaces for Dual WAN but my LAN1 basically doesn't work - it shows "Your ISP's DHCP does not function properly" error.  I can switch ISPs around and each of them work on WAN port but not on LAN1.  To make matters worse the DHCP server from ISP on LAN1 can talk to my internal network causing rogue DHCP server issues.

My router is RT-AX3000 on 3.0.0.4.388_25210 firmware.  The setup used to work, I only noticed DHCP and failover related issues this year.

[Silem2013]

I can replicate the problem when a guest WiFi is enabled - Microsoft Rogue DHCP checker doesn't see other DHCP when there is no guest WiFi set up and it detects the rogue DHCP when a guest WiFi is set up and enabled.  Disabling it still keeps the wrong DHCP visible, but I haven't restarted the router yet.

[Silem2013 · Accepted solution]

Status update: disabling guest network and restarting the router fixes the issue. 

It really looks like having Dual WAN and guest network doesn't work together for RT-AX3000. 

It's quite an exotic combination but I hope it's fixable - dual WAN failover is really nice for working from home and guest network is good for ... house guests, obviously.  Now I just have to figure out some Wireguard VPN issues.

[Alex52]

Wireguard VPN commonly causes issues back and forth. I used it myself only a week back with a new GT-BE98 Pro and tied my S24 cellphone to it before it started throttling my Spectrum Internet speeds from the router. When I saw that, I turned it off but forgot to remove it from the cellphone. I got up one morning to find my cellphone unresponsive until I  deleted the VPN  Wireguard settings from it. The Wireguard system uses distant servers here and there which is part of the problem, but again, much of the problem is with the ASUS software.  You also have to consider ASUS is trying to use a router hardware to fulfill the actions of a server. It's all a balancing act to properly utilize the router resources. That's partially why we're seeing erratic behavior after each ASUS firmware update. ASUS programmers evidently lack a full understanding of what they are trying to do and are working with.

[Silem2013]

I think I just used a wrong saved profile on the laptop - probably from the time before the factory reset.  I'd expect it to fail the connection but it connects and appear active on the laptop, just not routing anywhere.  I've deleted it and added the profile again and it works as expected.

[Alex52]

You're likely correct about that saved profile on the laptop. It almost makes you question yourself. Minor unseen SSID changes will affect connections after a factory reset of the router. I've experienced the same thing across bands and had to delete old profiles and create new ones using the exact same input when the adapter shows what are the same found network names using the same ID and security - as well as the same MLO or WiFi6/WiFi 7 profile.  I've come to expect it after any factory reset now. It may have something to do with DHCP assignment with the router.