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How can QoS be configured to prioritize VoIP traffic on congested links?
Asked on Oct 17, 2025
Answer
To prioritize VoIP traffic on congested links, Quality of Service (QoS) can be configured to ensure that voice packets are given precedence over other types of traffic. This is typically achieved by classifying and marking VoIP packets, then applying queuing mechanisms to prioritize them. Tools like Cisco IOS or Juniper Junos can be used to implement these configurations on routers and switches.
<!-- BEGIN COPY / PASTE -->
class-map match-any VOIP
match ip dscp ef
!
policy-map PRIORITIZE-VOIP
class VOIP
priority
class class-default
fair-queue
!
interface GigabitEthernet0/1
service-policy output PRIORITIZE-VOIP
<!-- END COPY / PASTE -->Additional Comment:
- Classify VoIP traffic using DSCP (Differentiated Services Code Point) marking, typically EF (Expedited Forwarding).
- Use a policy map to apply a priority queue to the VoIP class, ensuring low latency and jitter.
- Attach the service policy to the outbound interface where congestion might occur.
- Monitor and adjust the configuration as needed to maintain voice quality.
- Ensure that network devices along the path support and honor QoS markings.
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