Cisco CCNA (200-301)IP ServicesHard
A network engineer is troubleshooting an issue where a specific application's traffic from host 192.168.1.5 is experiencing severe delays, despite other traffic types functioning normally. The application uses UDP port 5000. The engineer suspects that a QoS policy might be misconfigured, causing this traffic to be deprioritized or dropped. Which 'show' command would best help the engineer identify if traffic from 192.168.1.5 on UDP port 5000 is being matched by any QoS policy on a Cisco router?
- Ashow running-config | section policy-map
- Bshow access-list 101
- Cshow class-map
- Dshow policy-map interface GigabitEthernet0/1 input
Show answer & explanationAnswer & explanation
Correct answer: D. show policy-map interface GigabitEthernet0/1 input
The 'show policy-map interface <interface-id> {input | output}' command provides real-time statistics and details about which traffic classes are matching on a specific interface and what actions (like policing, shaping, or queuing) are being applied. This is the most direct way to see if the application's traffic is being affected by a QoS policy.
Why the other options are wrong
- A. This command shows the policy-map configuration from the running config, but not real-time statistics or whether traffic is matching.
- B. This command only shows the access list configuration, not whether traffic is actually matching it as part of a QoS policy.
- C. This command shows the class-map configuration, but not its application to an interface or live traffic statistics.
QoS Policy Verification
To verify the real-time effect of a QoS policy on an interface and see if specific traffic is matching a class, use the 'show policy-map interface <interface-id> {input | output}' command.
- Provides live statistics on class matches and actions.
- Shows bytes and packets matched by each class.
- Essential for troubleshooting QoS implementation.
- Helps identify if traffic is being correctly classified and treated.
Memory trick: Show Policy-Map interface, see the traffic flow!