rDNS: Monitoring the Flip Side of DNS

DNS monitoring is an important part of keeping your services available. DNS is what allows your browser to turn the name ‘nodeping.com’ into the IP address Without proper functioning DNS, your website, email, and other services would be unreachable.

One often neglected part of DNS monitoring is the rDNS, or reverse DNS, entries. As the name suggests, rDNS is the reverse of DNS. It maps an IP address to a hostname using a special PTR DNS record type. In essence, it associates an IP address to a specific hostname or domain.

PTR records are used by all kinds of utilities and services like the humble ‘ping’ and ‘traceroute’ as well as more complex FCrDNS-enabled services. A forward-confirmed reverse DNS (FCrDNS) verification uses the PTR record to associate a domain owner with an IP address. It’s not a rock-solid form of validating ownership but is usually considered enough to be used for whitelisting servers for SMTP services because spammers usually can’t fake an rDNS record when they forge domains.

If you’re sending email from a server, you should have a proper PTR record in place that includes the domain for the ‘from’ address. This will help ensure your email from that server will not get sent to the spam bucket. A PTR, or ‘pointer’, record is usually configured by whomever owns the IP address so you often have to put in a ticket with your colocation or service provider to set or change rDNS entries.

NodePing is one of very few server monitoring services that can monitor rDNS entries. To set up a rDNS check, select ‘DNS’ from the check type and ‘PTR’ from the record type dropdown. It’s important to note that your PTR record will be in what is commonly called ‘arpa’ format. An example of the ‘arpa’ format for the IP is ‘’ – please note how the octets are in reverse order, not the numbers. Set the ‘arpa’ address for your IP address in the ‘Query’ text field. You’ll also want to set the ‘Expected Response:’ field to the hostname for that IP, example: ‘api.nodeping.com’.

For more information about rDNS/PTR monitoring or our DNS check capabilities in general, check out our DNS check documentation.

Replacing probe server [CZ] with [IT] in EUR region and IP changes for [AU], [TX] and [NJ]

Due to continued connectivity issues with our probe in  Zlin, Czech Republic [CZ], we’re replacing it with a new probe server in Milan, Italy [IT]. The new server will be brought online 2014-03-03.

Adding – Milan, Italy (IT) – IT (
Removing – Zlin, Czech Republic (CZ) – CZ (

Additionally, the IP address for the current probes listed below will also be changing on  2014-03-03.

AU will change from to
TX will change from to
NJ will change from to

Please update your firewalls appropriately.

A current and always up-to-date list of all the IP addresses for our probe servers can be found in the FAQ.

[UPDATE - 2014-03-03 08:37GMT-7] – All new probes and IP changes have completed.

NodePing mobile push notifications to wake you up!

We’re pleased to announce another new notification type for NodePing server monitoring. You can now receive persistent push notifications through Pushover on your iOS or Android device.

Once configured, each ‘down’ event for your check will push an ‘emergency’ notification to your device and automatically re-alert every 30 seconds until it is acknowledged, up to 5 minutes.  Try sleeping through that!

Pushover notifications are faster and more reliable than SMS and are currently the only NodePing notification type that will persistently re-alert you when a check fails. Please consider switching your SMS alerts to Pushover alerts. It will also help us keep NodePing prices down as Pushover alerts are significantly cheaper than international SMS.

Once installed, simply add your Pushover ‘user key’ as a ‘Pushover’ notification type in your contact record and select that key when creating or editing a NodePing check.

For those who may be interested in viewing your check status in a native iOS app, one of our customers has created HostCheck using our API.

Let us know in the comments what NodePing feature you’ve been itching to see.

How to integrate PagerDuty into NodePing

Many of our customers are also big PagerDuty fans. What’s not to like! PagerDuty offers great escalation and on-call hand-off capabilities as well as flexible voice, sms, and even pajama alerts.

To make it easier for you to integrate your already existing PagerDuty workflow, we’ve added a new contact notification type to NodePing. The ‘PagerDuty’ type accepts a ‘Service API Key’. You can find information on how to set up a PagerDuty generic API service at their support site.

Our system will send a ‘trigger’ event on each failure and a ‘resolve’ event on each recovery. Add an entry in your contact record by specifying your PagerDuty ‘Service API Key’ (they kind of look like a big random string “47b3a13848514c3fa3def842464eeaa8″) and selecting ‘PagerDuty’ in the notification type drop down. Then specify that contact when you edit or create your NodePing checks.


You can specify as many different PagerDuty contacts as you like. This allows you to use multiple ‘Services’ with NodePing and have full control of your PagerDuty escalations and notifications.

We strive to bring you the best solutions for your monitoring needs. We’ve set our eyes on Android and iOS push notifications next so follow this blog for that notification. We’d also love to hear from you. What notification types or other features would you like to see in NodePing?

If you’re not a NodePing customer yet, you can sign up for a free 15-day trial and kick the tires for yourself. We’re confident you’ll like what you find.

Adding Probes to NAM Region and IP Changes [LD] and [CA]

We’re excited to announce the addition of two more probe servers in the North America (NAM) region. They will be brought online 2014-01-20.

Denver, Colorado (US) – CO (
Chicago, Illinois (US) – IL (

Additionally, the IP address for the current probes listed below will also be changing on  2014-01-20.

LD will change from to
CA will change from to

Please update your firewalls appropriately.

We continue to strive to bring you the most reliable and economical server monitoring anywhere.

A current and updated list of all the IP addresses for our probe servers can be found in the FAQ.

[UPDATE - 2014-01-20 10:29GMT-7] – All new probes and IP changes have completed.

New East Asia/Oceania Region

We’re excited to announce we’re adding a new check region and probe servers in East Asia/Oceania to the NodePing server monitoring service.

The new region will be brought online and available for selection starting January 6, 2014. With this new addition, NodePing now has three distinct check regions, North America (NAM), Europe (EUR), and East Asia/Oceania (EAO).
NodePing Regions
The new probe servers are located in:

  • Sydney, Australia [AU]
  • Singapore [SG]
  • Hong Kong [HK]
  • Tokyo, Japan [JP]

IP addresses for the new probe servers can be found in the FAQ. Any questions can be directed at support(at)nodeping.com

[UPDATE - 2014-01-06 08:52GMT-7] – All four new probe servers in the EAO region are online and operational.


IP Address Changes – [LD]

Our probe server in London, United Kingdom [LD] will be changing IP addresses on 2013/12/09:
LD will change from to

No data loss is expected. We apologize for any inconvenience.
Please adjust your firewalls appropriately so your checks are not blocked.

A current and updated list of all the IP addresses for our probe servers can be found in the FAQ.

[UPDATE - 2013-12-09 13:29GMT-7] – LD IP address change complete


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