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New Member

VoIP & Qos & RTP priority


I have 2 routers 1750-4V (1 FXO & 1 FXS each other) and because I have

a low speed link (64 Kbps) I have to use QoS, and define Voip traffic with

high priority. I define multilink ppp, and ip rtp, like :

> ip rtp header-compression iphc-format

> ip rtp priority 16384 16383 40

So when there is Voip traffic I want to reserve 40Kbps for it, but when

there is no Voip traffic, I want to have all the 64 Kbps available for data

traffic, and feel is not working like that, because is too slow.

My question is, this rtp command reserve a fixed bandwidth,although is

there not Voip traffic ?

So which other QoS can I use to reserve 40Kbps only when I have Voip

traffic, and have all the 64 Kbps available when there is only data traffic


Thanks a lot for your suggestions.



New Member

Re: VoIP & Qos & RTP priority

I would implement Low Latency Queuing...take a look: Be sure to have at least 12.1.3T loaded on your 1750.

version 12.1

no service single-slot-reload-enable

service timestamps debug uptime

service timestamps log datetime msec localtime

service password-encryption


hostname 1750-LIVONIA-R1


logging rate-limit console 10 except errors

enable secret 5 $1$LGwO$AGYLm4SQlWaa1c9vwnYVO1


username 3640-LISLE-R1 password 7 060506324F41

memory-size iomem 25

ip subnet-zero

no ip finger

no ip domain-lookup



class-map match-all VOICE

match access-group 102



policy-map QOS

class VOICE

priority 128 (<--the bandwidth you want allocated to voice calls)

class class-default



isdn switch-type basic-dms100

call rsvp-sync









interface BRI0

description Backup to Frame Relay Lisle

ip address

encapsulation ppp

dialer idle-timeout 600

dialer wait-for-carrier-time 10

dialer map ip name 2610-LISLEFRAME-R2 broadcast 16303530368

dialer map ip name 2610-LISLEFRAME-R2 broadcast 16303530361

dialer hold-queue 75

dialer load-threshold 128 either

dialer-group 1

isdn switch-type basic-dms100

isdn spid1 73463201230101

isdn spid2 73463201240101

ppp authentication chap

ppp multilink


interface FastEthernet0

ip address

speed auto


interface Serial0

no ip address

encapsulation frame-relay

no ip mroute-cache

cdp enable

frame-relay traffic-shaping

frame-relay qos-autosense


interface Serial0.1 point-to-point

ip address

frame-relay interface-dlci 30

class FRAME

frame-relay ip rtp header-compression


router eigrp 1


default-metric 64 200 255 1 1500

distribute-list 1 out

no auto-summary

eigrp log-neighbor-changes


ip classless

ip route 240

no ip http server



map-class frame-relay FRAME

frame-relay cir 256000

frame-relay bc 2560

frame-relay be 0

frame-relay mincir 128000

no frame-relay adaptive-shaping

service-policy output QOS

frame-relay fragment 320

access-list 1 deny

access-list 1 permit any

access-list 100 deny eigrp any any

access-list 100 permit ip any any

access-list 102 permit udp any any range 16384 32767

access-list 102 permit tcp any eq 1720 any

access-list 102 permit tcp any any eq 1720

dialer-list 1 protocol ip list 100



line con 0

password 7 151C5902123E


transport input none

line aux 0

password 7 011D540A4D1F


modem InOut

modem autoconfigure type usr_sportster

speed 115200

flowcontrol hardware

line vty 0 4

password 7 030A0905101B


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