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How to prioritize voice traffic using c2621 and cisco IP telephones or other IP gateways through Frame Relay?

2621 is connected to Frame Relay and want to prioritize voice traffic going from Ethernet0/0 (other data traffic goes also via Ethernet 0/0)(using IP telephones or other IP gateways, which supports IP precedence)

Which type of queuing should we use (and how- the example would be the best) and what parameters should be set for FR links ?


Re: How to prioritize voice traffic using c2621 and cisco IP tel

IP precedence is really unecessary if you are

doing voip over frame-relay. The queuing mechanism would

be Ip rtp priority which create two queues. A high

queue for voip traffic and a low queue populated by the queue

mechanism used for data traffic. In the example below it is


Also to ensure good voice quality, large data packets

should be fragmented to reduce the propagation time across the link. The

frame relay tc should be kept at a small value to reduce

the maximum time we will need to wait for a token ( i.e. clocking of next frame on the wire)

Example below shown how these issues are addressed.

Interface ethernet 0

ip address


int ser 0/0

encap frame-relay

frame-relay traffic-shaping

no ip address


interface serial0/0.1 point-to-point

ip add

frame-relay interface-dlci 100

class voice


map-class frame-relay voice

frame cir 64000

frame bc 640

frame mincir 64000

frame-relay ip rtp priority 16384 16383 48

frame fragment 80

frame fair-queue 64 256

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