Cisco V3PN & QoS on ADSL Uk for VoIP

SoHo workers now share their lines with other PC’s in the house. The following is a config snippet from my router to provide some protection for my VoIP and business traffic.

! policy and classes to mark local incoming traffic
! whilst QoS pre-clasify should be used I have found it
! unreliable on certain IOS releases.  Also this allows us
! to be more specific about how we want to handle our traffic.
class-map match-all BIZAPPS1_VLAN1
 match access-group name BIZAPPS1    ! an acl to match biz apps
class-map match-all BIZAPPS2_VLAN1
 match access-group name BIZAPPS2    ! an acl to match biz apps
class-map match-all SCAVENGER_VLAN1
 match access-group name SCAVENGER   ! low priority stuff
policy-map VLAN1
  set dscp af21                      ! low drop probability
  set dscp af22                      ! med drop probability
  set dscp cs1
! Policy and Classes to on outbound connection
class-map match-all BIZAPPS
 match  dscp cs2  af21  af22  af23   ! all business aps
class-map match-any VOICE_SIG
 match  dscp cs3                     ! new dscp values signalling
 match  dscp af31                    ! old dscp value signalling
class-map match-all SCAVENGER
 match  dscp cs1                     ! unwanted traffic
class-map match-any IPCONTROL
 match  dscp cs6                     ! routing protocols etc
class-map match-all VOICE_RTP
 match  dscp ef                      ! voice packets
! Based on using no more than 30% for voice traffic this policy
! is enough for two voice calls (52k). DSL has a fixed uplink speed
! so I have used percentages to make carving up easier. Where a pipe
! which is likely to have speed changes it might be easier to use
! absolute 'bandwidth' statements to simplify calculations.
! NB: You cannot mix absolute and percentages in the same
! policy-map so decide up front what you are going to use.
policy-map V3PNWAN
 class VOICE_RTP
  priority 52 5348            ! 52k for 2 voice calls
 class VOICE_SIG
  bandwidth percent 5         ! 5% for call control traffic
  bandwidth percent 5         ! 5% for routing protocols etc
 class BIZAPPS
  bandwidth percent 30        ! 30% for business apps
  bandwidth percent 1         ! limit scavenger to 1%
  class class-default
! The device snippets are just enough info to show how the
! policys are applied and any other relevant settings.
interface ATM0
no ip address
no ip redirects
no ip unreachables
no ip proxy-arp
no atm ilmi-keepalive
dsl operating-mode auto
interface ATM0.1 point-to-point
 bandwidth 384                   ! your upstream speed
 pvc 0/38
 vbr-nrt 384 384                 ! your upstream speed
 tx-ring-limit 3                 ! tx-ring set to 3
 encapsulation aal5mux ppp dialer
 dialer pool-member 1
 service-policy out V3PNWAN      ! associate to phys interface
interface Dialer0
 ip tcp adjust-mss 542           ! make tcp packets much smaller
interface Tunnel0
 qos pre-classify                ! allow acls based on pre-encrypted data

Good luck


Sam Knows – LLU Information for the Uk

This is more of a memory jogger for me as I’ve been using this excellent site for years. So for my benefit as well as anyone else who needs it the URL is :

This is an excellent site originally setup by campaigners to find the latest information on broadband pre-registrations. Since then things have changed dramatically in the Uk. This site now contains excellent information on what services are via your own local telephone exchange.

This site will now be added to my links … !