HA IP - strange issue with base_url

I change my setup with cloudflare+traefik as reverse proxy ,
Previously my base_url was simply
Not with new setup i can only access it via http(s)://mydomain.com .
All working perfectly but i have some doubts:

strange - but i forgot to update the base_url and it still using ,
Where i cant from the browser with this IP.
Only with http(s)://mydomain.com .
how come it’s still working?this really confusing me …

by inspect the homeassitant docker netwrok:

"Containers": {
            "2c5d0697f7fe87217dxxxxxxxxxx7ad62e8bdc65a7920cf": {
                "Name": "traefik",
                "EndpointID": "04b4ab3e8a658fexxxxxxxxxxd2a8329f2a02b5422",
                "MacAddress": "02:22:22:1d:04:02",
                "IPv4Address": "",
                "IPv6Address": ""
            "546da201428a0dcb7fxxxxxxxxx3a824937624ee8574f10dba9f50c624": {
                "Name": "homeassistant",
                "EndpointID": "bb14061b00199e6292e7xxxxxx50f811ceaf303e4f9d51c0357bcb0cab",
                "MacAddress": "02:22:22:22:04:05",
                "IPv4Address": "****",
                "IPv6Address": ""


How come HA still working with this IP where actually i can’t connect with it?
Should I place the internal IP as base_url instead?
I guess i could also use http://mydomain.com but correct me if i wrong …
is this impact the performance as this it out to the internet and then connect back to server ?
Is there any IP i could use when connecting from browser (when working on same network)?