Dear, all,
I’m facing a problem registering softphone FreePBX with public IP on the Local network. (when I’m connected to my office Internet. I have deployed FreePBX in my office and using the same internet on FreePBX) and when I disconnect my office internet and turn on my Mobile data softphone registered successfully.
this problem is only when I connected to my office internet.
Please help me How I can set up DNS at my office Mikrotik Router to resolve the FQDN of PBX to its LAN address, while other DNS servers (when at home or on mobile data) resolve to the office public IP
Please help me in this regard.
Thanks

Add a static DNS record on your router pointing to the local IP, should be enough ?
When you connect on the network of that router, it will resolve to the local IP address.
When you are outside that network, it will resolve to the external address.
IP / DNS / static
I have tried adding Static DNS, Please help me If I’m not doing it in the correct way.
172.16.0.69 is LAN IP of FreePBX.

Looks ok to me.
And how are DNS settings in your DHCP config ?
Because if your clients are not passing your router for DNS, then the record will not be used.
It looks like that I think it’s not reading my static DNS entry

DHCP Network, set DNS server to your router.
ONLY router IP.
The other DNS (why 2 times the same ?) will be used by the router.
The client request DNS record from router. When the router does not have it in cache, it will request it from your other DNS.
And make sure to renew lease on client or it will “remember” the old setting.
Cmd: ipconfig /renew
Only router IP in DNS or my IP-PBX IP.
My Router IP is 172.16.0.1/16 and my PBX IP is 172.16.0.69
what I write here?
On your previous screenshot for DHCP network your have THREE DNS entries.
Remove the two for 8.8.8.8 and 8.8.4.4.
ONLY your router IP should be left there. NOT pbx (it doesn’t handle DNS !)
That way your client devices will request DNS from your router and only your router.
You DID renew the lease ?
From your client:
ipconfig / all
yes I have tried whe I renwe it assigin DNS = 172.16.0.1
but the internet stopped working
What router do you have ?
Can you export config ?
terminal: /export file=anynameyouwish
Move export to computer and review contents, remove serial number and any public WAN IP or passwords.
Then post between [ code ] quotes for easier readability.
I have Mikrotik CCR 2004-16G-2S+ arm64.