DNS Failover and Monitoring Documentation

Access to the DNS Failover

DNS Failover and Monitoring checks are an optional feature. By default, it is not included in the Free plans. Most of the paid plans support it with a fixed amount of available checks and rules.

Supported records

DNS Failover and Monitoring checks are supported both for IPv4 A records and IPv6 AAAA records. Each A and AAAA record can be configured separately, which means that the DNS Failover and Monitoring feature is fully compatible with Round-Robin DNS and GeoDNS configurations.

Available monitoring types

Currently, our DNS Failover and Monitoring checks system supports following monitoring types:

ICMP Ping - The system sends 12 ICMP ping checks to the given IP address. The packets are 4x 64bytes, 4x 512bytes, and 4x 1024bytes.
- Ping with 15% threshold - If 15% or more of the packets fails, the check is marked as DOWN.
- Ping with 25% threshold - If 25% or more of the packets fails, the check is marked as DOWN.
- Ping with 50% threshold - If 50% or more of the packets fails, the check is marked as DOWN.
Web checks - The system makes HTTP(S) request to the given IP address. The hostname, port, and path can be customized.
- HTTP - Check request is send over HTTP. If the request time outs or the returned response code is not 200, the check is marked as DOWN.
- HTTPS - Check request is send over HTTPS. If the request time outs or the returned response code is not 200, the check is marked as DOWN.
- HTTP with custom string in the response - Check request is send over HTTP. If the request time outs or the returned response code is not 200, or the returned response text is not equal to the defined custom string, the check is marked as DOWN.
- HTTPS with custom string in the response - Check request is send over HTTPS. If the request time outs or the returned response code is not 200, or the returned response text is not equal to the defined custom string, the check is marked as DOWN.
TCP - The system makes TCP connection to the given IP address on the chosen port number. If the connection is unsuccessful, the check is marked as DOWN.
UDP - The system scans the chosen UDP port number on the given IP address. If the connection is unsuccessful, the check is marked as DOWN.
DNS - The system makes DNS query for chosen hostname and query type on the given IP address. If the response is not equal to the expected response, the check is marked as DOWN.

Monitoring regions

You can use the monitoring regions to configure your records to be monitored only from a specific area. Here are the options:

Global - this is the default option, it sets your failover record to be monitored from all nodes globally.
Europe - your failover record will be monitored only from nodes located in Europe.
North America - your failover record will be monitored only from nodes located in North America (USA and Canada).

Monitoring regions are great options if you are runing GeoDNS and you want to monitor your nodes from the closest locations.

Supported countries

You can use the monitoring countries to configure your records to be monitored only from a specific country. Here are the options:

Austria - at
Bulgaria - bg
Brazil - br
Canada - ca
Germany - de
Spain - es
Finland - fi
Hong Kong - hk
Hungary - hu
Israel - il
India - in
Italy - it
Japan - jp
South Korea - kr
Mexico - mx
Netherlands - nl
Peru - pe
Poland - pl
Romania - ro
Russian Federation - ru
Singapore - sg
Turkey - tr
Taiwan - tw
United Kingdom - uk
United States - us
South Africa - za

Handling of DOWN events

To be marked as DOWN the DNS record should be detected as DOWN from two different checks on two different locations (check nodes). If only a single node returns a DOWN event, but the others report it as UP, the DNS record will not be marked as DOWN.

The DOWN event handlers define what will be happened with the monitored DNS record when it is detected as DOWN. Available options are:

Monitoring only - no changes will be applied to the DNS record. You will be notified by e-mail if the DNS record is detected as down.
Deactivate the DNS record - if the monitored DNS record is detected as down, it will be deactivated. The option is useful for Round-Robin and GeoDNS configurations.
Replace with working IP - it allows up to 5 backup IPs to be defined. If the main DNS record IP is detected as down, the system will check the backup IPs starting from the first till the last. The first IP which is detected as UP and working will be set to the DNS record.

Handling of back UP event

To be marked as UP the DNS record should be detected as UP from two different checks on two different locations (check nodes). If only a single node returns a UP event, but the others report is still as DOWN, the DNS record will not be marked as back UP.

The UP event handlers define what will happen with the monitored DNS record when the main IP address of the DNS record is detected as UP again after it is already marked as down. Available options are:

Monitoring only - The DNS record will continue to be monitored, once it is detected as down. No changes will be applied to the DNS record when it is detected as back UP. The monitoring will continue even after the check is detected as UP and you will continue to receive e-mail notifications if the check is going multiple times UP and DOWN.
Do not monitor, if the check is back up - When this option is chosen, once the DNS record is detected as DOWN and the down event handler is processed, the DNS record will not be monitored anymore. It will be required to be reactivated manually in order the checks to continue.
Activate the main IP, if it is back up - With this option, even the main IP is detected as DOWN, it will continue to be monitored. If the main IP is detected as UP again, it will be reactivated for the DNS record. This option is working both with the down events "Deactivate the DNS record" and "Replace with working IP".

Monitoring checks identification

We are monitoring all DNS Failover checks from multiple checks around the world. Here is the full list with our monitoring nodes: https://www.cloudns.net/wiki/article/379/

All the checkers can be fetched by DNS with the following hostnames:

IPv4 A record: ipv4.failover.cloudns.net

IPv6 AAAA record: ipv6.failover.cloudns.net

HTTP(S) requests made from the monitoring system are with the following User Agent:

Mozilla/5.0 (compatible; ClouDNS/1.0; +https://www.cloudns.net/dns-failover/)

It is possible the version (1.0 for now ) to be changed in future based on the updates of our system.

History

For each DNS Failover and Monitoring check, we are recording history both for the executed monitoring checks and for the taken actions on the DNS record. The history is stored for 30 days and can be seen in the control panel for each DNS record for which is activated a DNS Failover and Monitoring check.

Activation and deactivation

For all supported DNS record you can activate the DNS Failover and Monitoring check by clicking on the icon:

Once the DNS Failover is activated, the first monitoring check will be executed within a minute, and the details will be recorded.

The DNS Failover and monitoring check can be deactivated anytime when you need by "Deactivate this DNS Failover and Monitoring check" button.

Have a question? Check more on our DNS Failover and Monitoring check page and write to our Technical Support. We will assist you with all the questions you have.

Last modified: 2023-01-24

Wiki