One of our clients (lets call them Anon), have their DNS records hosted with a third party (lets call them DNSAnon). We (lets call us ALTDNSAnon), host the actual web server for Anon, and have two physically different SHDSL links entering our premises.
Each of the SHDSL links are provided by different vendors, and we have different public ip's assigned to each link. At any one time, we use one link as the primary, and the other as a secondary. In the event that the primary fails, we physically connect to the secondary. As that link has different public IP's we then have to get DNSAnon to change the IP addresses accordingly.
The main issue is that DNSAnon's DNS servers can then take up to 6 hours to propagate the changes which is too long. Our DNS servers propagate much quicker as they are directly hosted at a higher level in the DNS chain.
What I want to do is have some sort of redirection to our DNS entries from DNSAnon. For example, staging.anon.com.au which currently points to an IP address needs to point to staging.altdnsanon.com.au. This way I can make a simple change to the record for staging.altdnsanon.com.au which will propagate within 20 minutes or so.
There are a couple of contstraints;
1. Anon, don't want to move their DNS entries to us, so the primary records must stay with DNSAnon.
2. We can't use BGP as the links come from independent providers; if they were the same provider we could use BGP to solve all our problems.
3. Anon can live with 30 minutes of DNS propagation.
4. Anon can not live with up to 6 hours of DNS propagation.
Any ideas or suggestions would be much appreciated.