Downtime is a nightmare, and every network or app administrator wants to avoid it in any way they can. The longer the downtime, the greater the potential for a loss of revenue and a damaged reputation for the organization.
The critical applications hosted on the internet are always served from the primary site and, in the event of an outage, the traffic is rerouted to the backup site by either announcing the primary site IP prefixes from the backup site in Border Gateway Protocol (BGP) or making DNS record changes manually. The BGP announcement involves convergence time and a DNS record change wait for Time to Live (TTL) expiry. For a brief period, the application will be unreachable to end users.
The DNS failover helps admins drastically reduce this downtime by performing a simple DNS record failover configuration on their DNS hosting provider.
DNS failover
The DNS failover is an automated process that helps users specify multiple records for a domain and monitor those records from different locations. In the event of record failure, a monitor associated with the record detects the failure and makes sure that the failed record is removed from the equation. The DNS response is served only for available records.
Administrators must make sure, when setting up the DNS failover, that TTL for all recordings is equal and very low. This ensures that the downtime is minimal and that no manual intervention is required.
For an example, the www.manageengine.com domain has multiple records and when DNS lookup is performed on the site, those records are served in a round-robin manner. When a record fails, DNS continues to serve the failed record, and users may be unable to connect.
If the www.manageengine.com domain is configured for failover and all the records are monitored, the record failure is detected and only available records are served until the failed record is restored.
Figure 1:
Figure 1 shows the DNS lookup when all the resource records are monitored and all the records are reachable while polling. If the monitor associated with the record 127.0.0.1 detects IP is not reachable, the DNS response displays as shown in Figure 2.
Figure 2:
DNS failover with CloudDNS
ManageEngine CloudDNS supports DNS failover for multiple record types such as A, AAAA, ALIAS and CNAME. It also supports various failover strategies, such as active-active and active-backup. CloudDNS has more than 100 monitoring locations available worldwide to monitor DNS resource records
Sign up for a free, 30-day trial of ManageEngine CloudDNS and try various DNS failover strategies. You can also schedule a free, personalized demo with one of our solution experts to learn valuable tips and receive answers to your product questions.
