Bill Sandiford wrote:
The problem with relying on DNS for a failover solution is caching.
Many ISPs name servers cache their records. Even if you turn down
your TTLs, not all ISPs (especially the large ones) will respect
them. They will cache based on their settings.
The end problem is that when you have a failure, your DNS switches
over to point at your secondary VoIP server, but your clients all over
the world still end up getting the old DNS info from their ISP and try
and contact the dead server.
Or just setup multiple SRV records from the start and share the load
across both servers most devices that honour SRV records (in theory)
should flip between servers and this negates the problems you pointed
out above.
