Suggested Solution

Although your physical hardware might differ, Example 7-7 shows the output of the show auto qos command on R2 after entering the auto qos voip command for interfaces Serial 0/0 and Serial 0/1. Notice that cRTP and MLP are enabled only for interface Serial 0/0 since these link efficiency mechanisms are appropriate for slower link speeds (that is, link speeds less than 768 kbps), such as Serial 0/0's link speed of 128 kbps. However, these link efficiency mechanisms are not appropriate for higher-speed links (that is, link speeds equal to or greater than 768 kbps), such as Serial 0/1's link speed of 2 Mbps.

Example 7-7. Output from the show auto qos Command on R2

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R2#show auto qos
 !
  ip access-list extended AutoQoS-VoIP-RTCP
   permit udp any any range 16384 32767
 !
  ip access-list extended AutoQoS-VoIP-Control
   permit tcp any any eq 1720
   permit tcp any any range 11000 11999
   permit udp any any eq 2427
   permit tcp any any eq 2428
   permit tcp any any range 2000 2002
   permit udp any any eq 1719
   permit udp any any eq 5060
 !
  class-map match-any AutoQoS-VoIP-RTP-UnTrust
    match protocol rtp audio
    match access-group name AutoQoS-VoIP-RTCP
 !
  class-map match-any AutoQoS-VoIP-Control-UnTrust
    match access-group name AutoQoS-VoIP-Control
 !
  class-map match-any AutoQoS-VoIP-Remark
    match ip dscp ef
    match ip dscp cs3
    match ip dscp af31
 !
policy-map AutoQoS-Policy-UnTrust
 class AutoQoS-VoIP-RTP-UnTrust
  priority percent 70
  set dscp ef
  class AutoQoS-VoIP-Control-UnTrust
   bandwidth percent 5
   set dscp af31
  class AutoQoS-VoIP-Remark
   set dscp default
  class class-default
   fair-queue

Serial0/0 -
!
 interface Serial0/0
  no ip address
  encapsulation ppp
  no fair-queue
ppp multilink
ppp multilink group 2001100114
!
 interface Multilink2001100114
  bandwidth 128
  ip address 10.1.1.1 255.255.255.0
  service-policy output AutoQoS-Policy-UnTrust
  ppp multilink
  ppp multilink fragment delay 10
  ppp multilink interleave
  ppp multilink group 2001100114
ip rtp header-compression iphc-format

Serial0/1 -
!
 interface Serial0/1
  service-policy output AutoQoS-Policy-UnTrust
!
 rmon event 33333 log trap AutoQoS description "AutoQoS SNMP traps for Voice Drops" owner
 AutoQoS
 rmon alarm 33333 cbQosCMDropBitRate.1081.1083 30 absolute rising-threshold 1 3 3333
 falling-threshold 0 owner AutoQoS
 rmon alarm 33334 cbQosCMDropBitRate.1137.1139 30 absolute rising-threshold 1 3 3333
 falling-threshold 0 owner AutoQoS

Note

LLQ is appropriate for all interface speeds and is configured for both interfaces.