@Kevin_Z sure, here they are

And here's what happens when I try to re-enable the 192.168.22.2 reservation:

That's the DHCP part. The other half is the router's own IP. Here's the static config:

If I try to set it back to Dynamic IP, I lose internet connectivity. The 192.168.12.0/24 network is under my control and DHCP works fine in it. The only changes that I can recall between when it all worked fine and now are:

- I updated the firmware.

- I went from dynamic IP (192.168.0.0/24) to bypassing the outside router and getting an outside world IP on the Archer and then back to dynamic IP (192.168.12.0/24).

- The 192.168.12.0/24 subnet is my home DMZ. Devices in the 192.168.12.0/24 can be reached from devices in the 192.168.22.0/24 but the opposite is not true (this is normal, this is how I want it).

Here are some entries from the Archer log that I think might be relevant:

2021-03-02 11:35:03 imb[12838]: <6> 218011 ARP Binding enabled

2021-03-02 11:35:16 imb[3039]: <5> 218021 IP 192.168.22.2 and MAC 04:D3:B0:7E:A4:5F bound succeeded
2021-03-04 07:06:04 dhcps[31302]: <6> 212052 send offer ip 192.168.22.217 and dns 1.1.1.1 to fc:03:9f:07:a1:d9
2021-03-04 07:06:04 dhcps[31302]: <6> 212051 receive discover from fc:03:9f:07:a1:d9
2021-03-04 07:05:22 dhcps[31302]: <6> 212052 send offer ip 192.168.22.2 and dns 1.1.1.1 to 04:d3:b0:7e:a4:5f
2021-03-04 07:05:22 dhcps[31302]: <6> 212051 receive discover from 04:d3:b0:7e:a4:5f
2021-03-04 07:04:18 dhcps[31302]: <6> 212052 send offer ip 192.168.22.2 and dns 1.1.1.1 to 04:d3:b0:7e:a4:5f
2021-03-04 07:04:18 dhcps[31302]: <6> 212051 receive discover from 04:d3:b0:7e:a4:5f
2021-03-04 07:03:13 dhcps[31302]: <6> 212052 send offer ip 192.168.22.2 and dns 1.1.1.1 to 04:d3:b0:7e:a4:5f

All the while, IPv6 is still working fine.

Thanks,
Nacho

@Kevin_Z 

Hi!

Thank you for following up, here are some answers:

> After you upgraded the router firmware, did you reset it and reconfigure it?

No

> Or did you input the previous config file back into the router?

No, I didn't need to do it. The configuration stayed there between updates.

> It is suggested to delete the Address Reservation rules, and add them back manually again, check if it will work properly

All of them? Some are still working properly.

> As for the Static IP address concern, can you please provide the detailed network layout,

The layout is like this:

Proprietary ISP box gets WAN address on its fiber connection side.

On the Ethernet side, it has a DHCP server handing out 192.168.12.0/24 IP addresses.

In the 192.168.12.0/24 network area there are 2 devices: a Linux Debian server and the C7.

C7 is connected via Ethernet cable to one of the Ethernet ports of the ISP box.

> how is the C7 connected to the network, will it get a WAN IP address if you change the WAN connection type to Dynamic?

If I set the WAN connection in the C7 config to dynamic, what should happen is that the C7 should get IP address 192.168.12.5 from the DHCP (address reserved at the DHCP of the ISP box). Instead, it silently loses connectivity to the internet. I say silently because there's no indication other than all the devices on the C7 wifi (192.168.22.0/24) losing internet access. Other devices on the 192.168.12.0/24 are not having any problem.

Should I try resetting the router and reconfiguring everything? How can I preserve the OpenVPN server cert and config if I do that?

I'm not in a big hurry to fix it because everything is working with static IPs right now but I'm curious about what's happening and would like to go back to dynamic IPs in the near future. My theory is that the C7 is being unable to rewrite entries in the ARP table for some reason... It explains why the problem is happening both on the LAN side and on the WAN side.

Best regards,

Nacho