1. Need to change IP as soon as possible, but DNS record has huge TTL (e.g. 24h).
2. Client ISP DNS does not resolve my domain and it's absolutely not clear how to proceed from here. I don't have connections in huge ISPs, writing stuff to ISP support is as effective as throwing stones in the lake.
Funnily enough, for both cases, /etc/hosts or its Windows equivalent comes to the rescue.
1. 24 hours is not common at all for A records, it should be between 5 minutes to 60 minutes.
Perhaps you are thinking of NS records, which would only be changed very infrequently, and both the source and target systems should be up so that there's no loss of availability.
2. Never had that, it's more likely that you did something wrong rather it being an ISP issue.
Feel free to send me an email with specifics, the email is in my profile although in a cryptic format to avoid spam.
1. Need to change IP as soon as possible, but DNS record has huge TTL (e.g. 24h).
2. Client ISP DNS does not resolve my domain and it's absolutely not clear how to proceed from here. I don't have connections in huge ISPs, writing stuff to ISP support is as effective as throwing stones in the lake.
Funnily enough, for both cases, /etc/hosts or its Windows equivalent comes to the rescue.