Low Latency Queueing (LLQ)

A Cisco Certification Exam Review

By Chris Bryant, CCIE #12933

Configuring LLQ on a Cisco router is basically a four-step process. First, define the traffic to be queued with access lists.

R2#show access-list
Extended IP access list 155
permit udp 210.1.1.0 0.0.0.255 220.1.1.0 0.0.0.255 range 17000 18000
permit udp 210.1.1.0 0.0.0.255 220.1.1.0 0.0.0.255 range 20000 21000

Next, create the class map that will call the access list.

R2(config)#class-map VOICE_QUEUE
R2(config-cmap)#match access-group 155

Now, create the policy map itself. Use IOS Help to verify the unit of measurement of any Cisco routing command - it can be kilobits per second, megabits per second, or bits per second!

R2(config-cmap)#policy-map VOICE
R2(config-pmap)#class VOICE_QUEUE
R2(config-pmap-c)#priority ?
<8-2000000> Kilo Bits per second

R2(config-pmap-c)#priority 100
R2(config-pmap-c)#class class-default
R2(config-pmap-c)#fair-queue

Finally, apply the policy map with the service-policy command on the appropriate interface - and in the appropriate direction with the input or output option!

R2(config-pmap-c)#interface serial0
R2(config-if)#service-policy output VOICE

To your success,

Chris Bryant

CCIE #12933

chris@thebryantadvantage.com