How does DNS work and when should you have backup DNS?

Related questions

1. Why is WebRTC important?
2. How does nslookup work?
3. What is WebRTC IP leak?
4. Do VPNS use own DNS?
5. Can hackers hack through VPN?
6. What TTL should I use?
7. Does WebRTC work on Safari?
8. What is WebRTC detection?
9. What is DNS TTL?
10. Can you speed up DNS propagation?

Tags

1. #outage
2. #resilience
3. #master
4. #alternative
5. #secondary
6. #servers
7. #records
8. #reduce
9. #server
10. #known
11. #answering
12. #backup
13. #requests
14. #primary
15. #system
16. #periods