IP SLA monitoring with PRTG:
Keep the line open!


  • PRTG monitors the quality of your VoIP-connections

  • PRTG comes with special sensors for Cisco IP SLA monitoring


  • PRTG monitors quality of service without expensive hardware

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Unlimited version of PRTG for 30 days. After 30 days, PRTG reverts to a free version.
Or, you can upgrade to a paid license anytime.






IP SLA monitoring:
Optimize the quality of service of VoIP and your network

Lost connections and poor sound quality
 during video conferences and customer calls are extremely annoying. Frequently, calls have been planned well in advance and are unable to be rescheduled on short notice. For the smooth functioning of voice over IP and video streaming, a stable flow of data packets is a must. With IP SLA monitoring, you’ll ensure a high quality of service. And by preventing malfunctions and verifying service level agreements, you’ll save time and money.

PRTG monitors quality of service (QoS) in real time regardless of your hardware, and comes with special sensors at no extra cost. Expensive Cisco IOS routers are required for Cisco IP SLA monitoring which monitors a network’s various VoIP parameters. Even if you do not have IP SLA-compatible routers or switches, you can still keep an eye on the network quality between two random network nodes by using Paessler’s QoS sensors. To do so, all you need are two regular Windows computers. As a result, you’ll ensure the quality of your network connections without having to shell out exorbitant amounts for IP SLA-compatible hardware.

With PRTG, everyone will work with peace of mind.


An introduction to IP SLA monitoring with PRTG


Data collected


 i What is a sensor?

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, e.g. the traffic of a switch port, the CPU load of a server, the free space of a disk drive. On average you need about 5-10 sensors per device or one sensor per switch port.

View video (3:26 min.)

The PRTG comes with a Cisco IP SLA sensor that monitors the following parameters:

  • ICPIF (Calculated Planning Impairment Factor): Predefined combinations of packet loss and packet delay for VoIP
  • MOS (Mean Opinion Score): Calculation of the subjectively perceived connection quality based on parameters such as jitter and packet loss
  • Packets which arrive in the wrong order
  • Packets which arrive too late
  • Average VoIP Jitter value (a kind of packet delay)
  • Average round-trip time (network latency time)
  • Transaction RTT
  • Packet loss

While QoS sensors and the Cisco IP SLA Sensor query similar data, QoS sensors also calculate MOS. With the Cisco IP SLA Sensor, this value is read directly by the Cisco device.


Free Download

Unlimited version of PRTG for 30 days. After 30 days, PRTG reverts to a free version.
Or, you can upgrade to a paid license anytime.


How IP SLA monitoring with PRTG works

VoIP connections are susceptible to even the most minor of problems. At the same time, it is extremely important that they comply with service level agreements (SLAs). If data packets do not arrive on time, get lost, or become mixed up, then the quality of the connection will drop dramatically. For optimal quality of service, jitter and packet delay variation (PDV) values should be as low as possible; packet losses, duplicate packets, and packets arriving in the wrong order must be avoided at all costs. The PRTG Network Monitor is a VoIP monitoring software that uses a variety of sensors for QoS monitoring and for the presentation of these values: the QoS sensor (in the variants QoS (Quality of Service) One Way and QoS (Quality of Service) Round Trip), the SNMP Cisco CBQoS sensor and the Cisco IP SLA sensor.

IP SLA Sensor: Cisco devices with the IP SLA feature gather various information about VoIP-related parameters, such as response time, latency time, jitter, packet loss, and packet delay. The most interesting values for VoIP are the mean opinion score (MOS) and ICPIF. The PRTG IP SLA Sensor monitors all these results. PRTG can be used as IP SLA monitoring software without extra add-ons or costs. In addition, the SNMP Cisco CBQoS Sensor lets you use Class-Based QoS when monitoring Cisco devices.

QoS sensors: When monitoring quality of service, PRTG deploys QoS sensors which verify the quality of a network connection between two end points. VoIP jitter, packet loss, packet delay, and other relevant values are measured. QoS sensors provide similar values to those gathered by IP SLA monitoring but are not limited to monitoring Cisco routers which include the IP SLA feature. PRTG is not just a LAN monitor: by using “remote probes,” you can even monitor quality of service via VPNs, WIFI and WAN connections.


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Free Download

Unlimited version of PRTG for 30 days. After 30 days, PRTG reverts to a free version.
Or, you can upgrade to a paid license anytime.



Configuring IP SLA monitoring

When configuring the PRTG IP SLA monitoring, you’ll need to add the IP SLA-compatible Cisco device you wish to monitor to PRTG by indicating its network address. Be sure to enter the SNMP access data correctly, for PRTG uses SNMP to query the corresponding IP SLA data of target devices.

Next, create a new sensor on this device to represent your Cisco router or switch in PRTG: on the device, click on “Add Sensor” and enter “IP SLA” in the search field. Then add the “Cisco IP SLA” sensor, and on the following screen select the parameters you wish to monitor.

Within minutes, the current values will appear on your PRTG dashboard - Your IP SLA monitoring is up and running.


VoIP connection quality at a glance
 – even on the go

PRTG can be started within minutes and it's compatible with many mobile devices.


PRTG comes with all the features you need, plus more your IT infrastructure won't want to live without.


PRTG monitors these vendors and applications, and more, in one view!



Free Download

Unlimited version of PRTG for 30 days. After 30 days, PRTG reverts to a free version.
Or, you can upgrade to a paid license anytime.



7 good reasons to choose PRTG as your IP SLA monitoring tool

Successful video conferences instead of lost connections

Successful video conferences instead of lost connections

VoIP monitoring lets you optimize the stability and sound quality of video conferences. Save yourself the embarrassment of lost connections and horrible sound quality.

Custom notifications

Custom notifications

Should parameters fall below or exceed your self-defined threshold values, PRTG will inform you immediately by email, SMS, or push notification – wherever you happen to be.

Automation for a lighter workload

Automation for a lighter workload

It’s impossible to monitor the quality of all VoIP connections manually. With PRTG, you can sit back and relax knowing sensors are doing the work for you – and that you’ll be notified automatically if a problem arises. 

Connection and bandwidth consumption optimization

Connection and bandwidth consumption optimization

PRTG lets you keep an eye on your bandwidth over a longer period of time, and recognize the times when utilization PRTG will show you how applications and services use bandwidth, which in turn will enable you to develop specific solutions for all your business needs.

Verification of service level agreements

Verification of service level agreements

By monitoring VoIP and verifying quality of service, IT services will become an aspect of your company which employees can count on in their day-to-day work.

Special IP SLA sensors at no extra charge

Special IP SLA sensors at no extra charge

Paessler charges no extra costs for the monitoring of IP SLA-compatible hardware. IP SLA is simply incorporated as another sensor type, and can therefore even be used as freeware.

Compatibility with all hardware

Compatibility with all hardware

With QoS sensors, the quality of service of VoIP connections can be monitored even in the absence of Cisco devices.


PRTG simplifies your day

Our monitoring software works for you and promptly notifies you of potential issues.
It frees you to concentrate on your day-to-day tasks with peace of mind.


PRTG saves time

With PRTG, you get one central monitoring tool for your servers and entire network. Enjoy a quick overview of your whole infrastructure via our dashboard and app.

PRTG saves worry

Customizing PRTG is a breeze. Getting started or switching from another network monitoring tool is easy thanks to the auto-discovery and pre-configured device templates.

PRTG saves money

80% of our customers report substantial or even exceptional cost savings in the area of network monitoring. The experience shows that the costs for licenses have paid for themselves within a matter of weeks.



Over 95% of our customers recommend PRTG


Paessler AG worldwide trialled PRTG in over 600 IT departments.
The aim was to tune the network monitoring software closer to the needs of the administrators.
The result of the survey: over 95% of the participants would recommend PRTG - or already had.

Recommend PRTG


You want to know more about other network-related monitoring topics?

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PRTG as network discovery tool

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Log monitoring with PRTG

Network utilities

PRTG supports a variety of protocols like SNMP, NetFlow, IPFIX or packet sniffing



PRTG The Swiss Army knife

PRTG: The Swiss Army knife for sysadmins

Adapt PRTG individually and dynamically to your needs relying on a strong API:

  • HTTP API: Access monitoring data and manipulate monitoring objects using HTTP requests
  • Custom Sensors: Create your own sensors for customized monitoring
  • Custom Notifications: Create your own notifications to send alarms to external systems
  • REST Custom Sensor: Monitor almost everything that provides XML or JSON


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More than 300,000 sysadmins love PRTG

PRTG is used by companies of all sizes. Sysadmins love PRTG because it makes their job a whole lot easier.

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Network Monitoring Software - Version (September 21st, 2021)


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