Monitoring Cisco Devices With PRTG – Part 1/3

Published by Florian Staffort
Last updated on March 03, 2022 • 10 minute read

As a network administrator, you know about the power and importance of Cisco devices. Whether you use Cisco routers, switches, access points, or VoIP (Voice over IP) solutions within your network-PRTG Network Monitor provides the exactly right sensor that will deliver the data you need to keep your network running smoothly.

monitoring cisco devices with prtg dedicated sensors 1

Being a member of the Cisco Developer Network, we not only have long-term experience with Cisco, but also in gathering important information from these devices and placing them at your disposal.

Besides offering several sensors that you can use with Cisco systems (for example, NetFlow sensors), PRTG offers 7 sensors specifically designed to monitor Cisco devices:

1. Cisco IP SLA Sensor

IP SLA (IP Service Level Agreement) is part of the Cisco IOS Software. It uses active traffic-monitoring technology to monitor continuous traffic on the network, thus being a reliable method in measuring overhead network performance. Our Cisco IP SLA sensor enables you to monitor relevant network parameters of important IP applications and IP services, like for example VoIP, through IP SLA results from Cisco devices via SNMP (Simple Network Management Protocol).

Regarding IP SLA, PRTG supports the following operations:

echo
pathEcho
fileIO
script
udpEcho
tcpConnect
http
dns
jitter
dlsw
dhcp
ftp
path-jitter

With the dns operation, for example, you can measure the DNS (Domain Name System) response time which is computed by calculating the difference between the time taken to send a DNS request and the time a reply is received. For VoIP, especially the jitter operation is important because it measures the variance in inter-packet delays between the source and the destination, as well as the other way around. For an IP service, such as VoIP which is extremely sensitive to inter-packet delay and packet loss, this operation is definitely one to remember.

The IP SLA sensor will provide you with live values for the following parameters, so you see all relevant information about QoS (Quality of Service) in your network:

Average RTT (Round-Trip Time)
Average Jitter (Destination - Source/Source - Destination)
Average Latency (Destination - Source/Source - Destination)
Downtime
ICPIF (Calculated Planning Impairment Factor)
Late Packets
Maximum/Minimum Latency (Destination - Source/Source - Destination)
Maximum/Minimum RTT
MOS (Mean Opinion Score)
Packets Lost
Packets Out Of Sequence
DNS RTT
TCP RTT
Transaction RTT

ICPIF, for example, represents predefined combinations of packet loss and packet delay in a VoIP network call and is a standard for measuring QoS. Another important parameter is MOS, which also is a well-established metric to obtain the quality of VoIP. By providing a numerical indication of the perceived quality of received media after compression and/or transmission, it gives you an overall benchmark for QoS in your network. When using the MOS channel in the IP SLA sensor, PRTG directly monitors this value on the device and no further internal calculation is needed.

Most vendors of monitoring solutions charge extra if you want to monitor IP SLA. Following Paessler's long term "all-in" policy we simply include this as one of our sensor types, with no extra charge. With PRTG you can even use the Freeware Edition to monitor IP SLA!

Note: Even if you do not have an IP SLA enabled device, you can still get similar information about line qualities with PRTG's QoS sensors.

2. SNMP Cisco ADSL Sensor

With the SNMP Cisco ADSL (Asymmetric Digital Subscriber Line) sensor, PRTG offers a solution to monitor the ADSL statistics of your Cisco router. Because it queries the data via SNMP, it only requires minimal bandwidth and CPU cycles to help you keep track of:

Downlink and uplink
Remote and local attenuation
Remote and local SNR (signal-to-noise ratio)
Remote and local power output

As you can see with the SNMP Cisco ADSL sensor, PRTG provides an easy and efficient way to monitor the connection quality of your Cisco router's ADSL connection.

3. SNMP Cisco CBQoS Sensor

With the SNMP Cisco CBQoS (Class Based Quality of Service) sensor, you can use PRTG to monitor your network parameters using Cisco's CBQoS via SNMP. This sensor supports the classes Class Map, Match Statement and Queueing and helps you monitor the following values:

Current and maximum queue depth
Pre policy packets
Pre and post policy size
Drop packets and size
Drop packets without buffer
Fragment packets and size

Because you and your colleagues usually work with bandwidth demanding IP applications and services to do business and, thus, rely on high QoS in your network, you probably already have implemented your own CBQoS policies on your Cisco routers. Besides IP SLA which is an active response time measurement method that uses reliable, scheduled continuous traffic generation to monitor network performance, CBQoS is a passive method to measure response time. This sensor is best used to monitor data that includes summary counts and rates by traffic class before and after the enforcement of previously defined QoS policies.

PRTG's CBQoS sensor helps you to:

analyze the different traffic classes in your network,
monitor the efficiency of your QoS policies,
and take the right measures when you need to amend your QoS policies to meet new challenges in an ever changing IT environment.