Need a little help my friends from another land.

Got site A and site B.

Site A has it's own Internet, DHCP server running on RB2011 (192.168.10.0/24).
Site B has it's own Internet, DHCP server running on RB2011 (192.168.20.0/24).

Both sites are connected using IPSec - runs great for 2 years (site B connects to various Windows servers on site A).

Now, I just bought RBwAPG-60ad kit - everything is up and running (mostly on defaults). MASTER and SLAVE gets their IPs sometimes from site A and sometimes from site B. Becasue of two DHCP servers.

I want to achieve this:

Users from site A let's use Internet from site A as it used to be. Users from site B let's use Internet from site B as it used to be. I want to keep DHCP servers on both sites running as it used to be, I just need access from Site A LAN to Site LAN B and vice versa using RBwAPG-60ad kit link.

Theres always someone at work (at site or remotely) so I need to make changes without testing and stuff.

You can't just bridge two networks like this. Take a free ports from each RB2011, remove it from bridge/switch, add some connecting subnet to it (e.g. 192.168.15.1/24 on one side and 192.168.15.2/24 on another), connect your new 60G link to these ports, then add routes (192.168.10.0/24 via 192.168.15.2 on one side and 192.168.20.0/24 via 192.168.15.1 on another), adjust firewall if needed and live happily ever after.

What ROS are you running on this devices?

Regards.

I was just going to suggest what Sob already did. I came up with exactly same idea as it is reliable and simple solution.
You may actually even improve it by adding route to 0.0.0.0/0 via the connected link with higher distance than your default WAN in order to do failover connection - if one site internet fails, it will get routed through second site.

As this config suggested by Sob is really basic, it does not matter what ROS is running there - even ROS 2.9 could to that.