Very likely if it's not the Gateway
Broadband IP address: 81.136.55.xxx
Default gateway: 172.16.13.191
Primary DNS: 81.139.56.100
Secondary DNS: 81.139.57.100
If you really want to determine if it is on your LAN, very carefully unplug the fibre cable from the ONT to disconnect from the internet and see if the address is still pingable. This is at your own risk.
If it is pingable with the fibre disconnected but not with the ONT depowered, it must be the address of the ONT.
Be interesting to see the result of that. The ONT is the other side of the router WAN interface so I would still not expect 192.168 to reach it.
Thanks for the suggestion of unplugging the fibre cable from the ONT. Good idea!
I did this and pings timed out, so this IP MUST be outside of my LAN and not the ONT itself.
What result do you get if you try trace root to the ip address?
Have done a few trace routes and that IP doesn't show as a hop to external hosts either.
This private IP to me, looks like a private device within BT's network. I suspect a customer/client device with broadcast subnet.
Yes, 172.16.13.191 is the BRAS, it can't be beyond that as it isn't routable.
I get the same via a different BRAS.
Possibly the address of the device used to update/access BT Hubs throughout the network.
I also get the same result but with a different BRAS