Despite its many benefits, VoIP is not immune to problems and
issues that can arise during use, and that's where you come into
the picture to troubleshoot those issues.
In this module,
we will explore some of the common problems and causes of VoIP issues.
We will also discuss the best practices for troubleshooting
VoIP issues. So, let's start with the most common problems
that can occur with VoIP systems.
Sometimes the users complain that they are unable to make or
receive calls, or their calls are being dropped, and this
could be due to many reasons.
Let's start with the feature and function configuration‑related
issues. Call routing is the most important feature of Unified
Communication and collaboration for the end users.
So the configuration related to call routing is also
quite critical. In my experience,
many times users complain that they are not able to make or
receive calls, or some features like call hold,
call transfer,
call conferencing, or the music on hold is not working
for them. And when I dug deeper,
I realized that it was due to the simple misconfiguration,
the VoIP administrator simply did not follow the step‑by‑step process and
missed something or the other, and that really caused a problem.
So the first step to troubleshoot any such issue is just to
go ahead and validate the configuration.
If you know how to configure different functions and features well,
you can troubleshoot them as well.
So following the configuration and feature guides will help you the most here.
It's highly recommended to recreate the issue in your own
lab first so you know the feature well,
and then you will be confident and in a better
position to validate the configuration.
Many other components like the configuration of the SIP
trunk that connects your VoIP system to the IP telephony
service provider configuration, or firewall‑related configuration,
basic network settings, such as incorrect network mask,
gateway‑related configs, or DNS server IP addresses,
or the Quality of Service (QoS) settings,
these all cause network congestion, packet loss,
and even call drops.
So make sure you build and validate the complete infrastructure from
physical connectivity to the network devices, firewalls,
and even at the application level where you configure your phones,
features, and functions. All the components work together to make a
successful VoIP call. Then comes another common issue where some or
more users are not able to make or receive calls. Or, maybe they are
able to call local calls, but not long‑distance calls or international calls.
When you check the configuration,
most of the time you would find that the users do not have
enough privilege to make certain type of calls.
For example,
an internal call to another team member or a call to another
site, or a call to another department, or maybe to the
outside PSTN network. For instance,
a user complains to you that he is unable to make a call from his
office in New York to another internal user in London,
and the call fails. When you check the configuration,
you realize that this user does not have the privilege to call between two
different sites, since calling privilege can be configured for each call
type, so calling privilege‑related configuration is an important item to
look at to deal with such issues.
Users still love their physical IP phones at their
desks to make and receive calls, and to work,
these IP phones register with the call processing servers. And, you
would realize that although the device registration seems pretty simple,
a lot depends on the underlying network and reachability from these IP
phones to the call processing servers, and then the correct
configuration for the devices as well.
Different devices support different protocols to talk to the call agent
server, like SSCP or Skinny protocol, or the SIP protocol.
Although most of the devices today have started to support SIP protocol lately,
and that has eased out the device registration process. It is still
difficult to register third‑party devices sometimes, so, make sure
that the device is supported in the UC infrastructure you're
supporting and that you follow the vendor‑specific configuration guide to register these endpoints.