I have two WAN from different providers, I would like to know how can I manage an IP failover to switch services in case of failur of the primary WAN. The only solution that I know is to use dns records and switch them in case of failure.
- Is there any service to switch them automatically?
- If I set a low TTL for my dns records can I be sure a fast switch from clients all over the world? Do DNS cache servers consider my TTL settings?
KEMP load balancers are an example of load balancers that monitors the backend servers and updates the DNS A records that it serves. It can do "active/active" load balancing by giving back multiple A records, i.e. round robin load balancing; or it can use "active/passive" load balancing, only giving back the second A record when the first fails.
As for the time-to-live (TTL; not TLS!) of your resource records, most DNS resolvers cach them correctly so a low TTL will allow for a quick failover. It is rumored that there are (were?) ISPs that modify their installation of BIND to artificially increase the TTL of records they cache, but I do not believe that is still the case.