You have recently moved to a new company as a network administrator and you've started doing an audit of the existing network.
Your network uses an end-to-end QOS approach between multiple offices. Access switches trust QOS markings received from IP Phones and higher layer devices trust the markings received from access switches, as seen in diagram below.
During your audit, you've discovered that MLS QOS is not enabled on one of the access switches in Office-1 (access-4):
Access-4#sh mls qos QoS is disabled
You checked entire configuration for Access-4 switch and notice that everything is configured identical to all other existing access switches with the exception of the fact that MLS QOS is disabled globally on the switch. So, you take the initiative and enable MLS QOS on it.
Not so long after you did that, you are contacted by server team about the following: they run a LAB-1 SERVER connected to that switch (Access-4) that is used to test some new applications that are very sensitive to delay and jitter - and they complain that this application is reporting errors due to high latency that started few hours ago (aproximately same time you enabled QOS on the access switch).
You did not change anything on the port configuration. You only enabled QOS globally (as part of standard config for all switches).
Why communication between Lab-1 and Lab-2 servers experience high delays ? What is the solution to solve this problem ?
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Costi is a network and security engineer with over 10 years of experience in multi-vendor environments. He holds a CCIE Routing and Switching certification and is currently pursuing same expert-level certifications in other areas. He believes that the best way to learn and understand networking topics is to challenge yourself to fix different problems, production-wise or lab-type exams. He also enjoys teaching networking and security technologies, whevever there is an opportunity for it.
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