Yes you can setup config sync only. However somethings are automatically converted for use on the secondary during the sync. Mostly the CARP VIPs which you wouldn't be using but also notably the DHCP server config. If you use Kea that wouldn't be an issue in 24.03 and in 24.08 you can disable it.

@balmmva
A WAN interface behaves basically like any other. So for HA you need three IPs in a subnet.

However, CARP isbnot compatible with PPPoE. You will have to put a router in front of the WANs.

@edgarquadros If it's only on one VLAN, be sure everything is tagged through your switches like the rest.

I have actually figured out how to setup the automated unit tests to run, so my code changes have passed all the required tests and I'm just waiting for the fix to be accepted. Hopefully the patch will be rolled out soon.

@Gertjan
Looks very similar. Thank you!

I have some new information about this problem. Unfortunately, I still haven't solved it.

Today I discovered that by changing the NAT settings I am able to restore full internet speed.
If I select the "WAN interface" option in "Translation Address", the full speed appears. However, if I select "CARP WAN VIP", the speed drops to a few Mbit/s.

I recorded packets with wireshark from the WAN port.
Both IP addresses (IP Address from WAN interface and CARP WAN VIP)
come out with the same MAC Address.

Maybe this is the problem?

I tried to connect a switch + two routers to the cable from the ISP in which I set the same MAC Address but different IP addresses.

After starting the routers, they interfered with each other and worked interchangeably, but neither cut the other's speed. Maybe if they came out of the same physical device, there would be a different symptom.

Maybe it is somehow related to the ISP. But I can't confirm or deny it.

Does anyone have any ideas what it could be?

@mikethiessen Thank you, I ended up doing just that and once the 8th spot was made, I deleted the other 2.

@Tadmin
A CARP setup requires at least two IPs within a subnet for the two nodes and a shared CARP VIP. All three have to be static to get CARP work out of the box. A shared DHCP VIP is not supported.

However, people posted workarounds here to get it up with DHCP as far as I remember. But this needs some scripting. Try the forum search.

@Phelton Don't know what you mean by your last comment but make sure that BASE is e.g. 1 on main and at least 100 on secondary. Also, use a different VHID Group for each network/carp ip

@MrPete You, Sir, are a lifesaver! I spent quite a couple of days figuring this out with no avail! Thank you a hundred times!!!

FWIW : I have moved all AD Server to the dhcp lan subnet, removed the ra server configuration, removed the virtual IP to have a second subnet, and all works flowlessly.

It seems ipv6 virtual ip routing is not working as expected on the LAN side.

@antoinef67 I registered an account just to say thank you sir, a life saver!