DNS Failover Basics
What is DNS failover?
DNS failover is in fact a two-step process. The first step is to actively monitor the health of your servers. Our monitoring servers check every few minutes based on your monitoring criteria to ensure that your service is running. The second step comes into play when downtime is detected. DNS records are dynamically updated in order to resolve traffic to a backup host. Email notifications are also sent out with the critical information on the failure.
Do I need to host my DNS with you?
If you use failover options that require changing the DNS records for your domain name, you will need to manage your DNS with us. If you simply want to monitor your service and get notified about downtime, you do not have to host your DNS with us.
Pricing
Do you offer a free trial?
Yes. We offer a 14-day free trial for 3 monitors. You do not need to provide any personal information or credit card number to start the trial. At the end of the 14 days, you can switch to a paid service.
How much does the service cost?
The cost of System Monitoring & Failover service is based on the number of monitors that you set up. To start with, 5 monitors costs $9.99/year. You may check the pricing here.
I ordered Monitoring & Failover service with 5 monitors, can I add more monitors later?
Yes. You can upgrade to 10, 50, 100 and 500 monitors as per your need.
Monitoring
What is a monitor?
A monitor is basically a certain criterion that you set up to ensure that your server is up and running. For example, you can set up a port check monitor on port 25 of your mail server if you want to make sure that SMTP is running normally on your mail server.
What are the monitoring types that you offer?
We currently offer the following monitoring types and are constantly adding more protocols:
HTTP(s) on a given URL
Keyword check on a given URL
Ping on a given host or IP
Port check on a given host and port
What services do you monitor?
Services are monitored on a given host or IP for a variety of protocols including HTTP, HTTPS, DNS, SSL, PING and TCP/IP port. Services monitored include but are not limited to
HTTP: Web server - port 80
HTTPS: Secure web server - port 443
Keyword: Response of HTTP/HTTPS request
SSL: SSL certificate expiration
PORT: Monitor any TCP port connectivity
FTP: File transfer server - port 21
SMTP: - inbound port 25
SSH/SFTP: Secure shell port 22
PING: ICMP echo
How does keyword check work?
A keyword check in a given URL ensures that the right page is displayed, not just any page. This way, you can detect error pages or defaced pages easily and distinguish them from the correct page. Our monitoring server checks for the keyword in the page source returned by the given URL and triggers an alert if the keyword is (not) found. The keyword can be any word on the HTML page or in the page title.
How often do you check my server?
We poll your server as often as the check interval you set up. The check interval can be set anywhere from 5 minutes to 8 hours.
What IP ranges should I whitelist to allow proper monitoring?
Please whitelist the following IP ranges to ensure proper monitoring.
162.216.242.0/24
72.51.58.0/24
142.202.188.16/29
45.79.53.60
45.79.139.177
45.118.133.11
139.144.225.233
139.162.105.137
139.162.195.230
139.162.241.248
172.105.98.207
172.105.178.214
172.233.26.38
172.234.120.164
172.234.160.126
172.237.28.155
172.237.74.106
172.238.42.108
194.195.117.202
194.195.123.102
2602:ff23:0:8888::/64
2a01:7e00::f03c:91ff:fedd:6af1
2a01:7e00::2000:9eff:fe08:df8f
2400:8901::f03c:93ff:feed:6cc2
2400:8902::f03c:91ff:fee5:9f03
2400:8904::2000:8eff:fe76:5e68
2400:8907::f03c:92ff:fe79:ad70
2400:8907::2000:2aff:feb6:f0f6
2600:3c00::f03c:93ff:fe2b:cc64
2600:3c00::f03c:93ff:fe2b:8509
2600:3c0a::2000:ccff:fe1b:a62f
2600:3c0d::2000:77ff:fee1:7bb6
2600:3c03::2000:e4ff:feaf:b244
2600:3c04::2000:b7ff:fec5:857c
2600:3c07::2000:16ff:fec0:4a88
2600:3c09::2000:39ff:febe:0444
2600:3c15::2000:31ff:fef0:ccc7
2600:3c18::2000:7dff:fed2:103a
I have a web server and a mail server. I want to monitor and failover both. How many monitors do I need?
For this scenario, you will need at least two monitors. One to monitor the SMTP server on port 25, and the other to monitor the web server on port 80. You can also add additional monitors such as keyword check monitor to make sure that the web page is returning the correct content or ping for the server hosts etc.
Getting Notified
Will I get notified if a monitor is down?
Yes, you will get notified. When setting up a monitor, you can set a group of notification contacts who will get alerted when the monitor is down. The contact could be an email address or a mobile phone number to receive SMS.
What kind of notification methods do you support?
We offer free email notification and EmailToSMS notification. SMS notifications will be implemented and you can purchase credits for a certain number of SMS.
Failover Actions
What failover methods do you support?
You have the following Failover options if your server is detected down:
Disable the failing A record and enable a backup IP for your domain name
Disable the failing AAAA record and enable a backup IPv6 for your domain name
Enable or disable a CNAME record
Enable or disable an MX record
Redirect to a custom URL
Failover to an offline page that displays a custom offline message
Do I need to host my DNS with you?
If you use failover options that require changing the DNS records for your domain name, you will need to manage your DNS with us. If you simply want to monitor your service and get notified about downtime, you do not have to host your DNS with us.
What TTL should I use for my DNS records?
Due to DNS caching, using a TTL between 60 to 180 seconds for your DNS records is suggested to reduce downtime to a minimum. In DNS, TTL specifies how long a resolver is supposed to cache (or remember) the DNS query before the query expires and a new one needs to be done.