Are you using the same FQDN for the gateway as before? If so, and clients can't communicate with the gateway, then you'll need to run brokerconfig again on your clients.
For clients that do connect to the LAN where the core is located, you can simply set up a policy to run "brokerconfig.exe -r."
If you have clients that only connect to the core through the gateway, then you will need to run brokerconfig.exe manually on each machine. If you have a lot of machines like this, you may just want to open a ticket with LANDesk Support to see if there is a better way.
Unfortunately I have above 500 comps out of LAN. Before installing clients I made some tests, and clients could connect using FQDN after change. Now it isn’t work. Of course Gateway FQDN is the same, only IP address is different.
I found, settings are in broker.crt file!
They are also in the hash (or .0) file.