Scenario#1 – VG224 – Strange DTMF behaviour

Problem description:

One of my customer reported an issue with their VG224. All Polycom conference phones connected to the Vg224 were facing an strange issue of DTMF tones not recognized by PSTN. Users trying to get into a MeetMe conference were having  tough time as their pin was not getting recognised.

Analysis & Observations:

This issue was passed onto me after some of my colleagues already spent few days trying all sort of things for resolution. I found out from the customer that the phones never worked properly ever since they hooked them in VG224. One thing was clear from this statement that nothing changed on Vg224 or on their network as this has been a known issue since they started using VG224.

I checked the gateway which was a SCCP configured VG224. For your information let me share how a SCCP VG224 is configured:

Configuration:

service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!

!
no aaa new-model
clock timezone GMT 0
clock summer-time BST recurring
!
!
!
stcapp ccm-group 10
stcapp
!
voice-card 0
!
!
!
voice service voip
fax protocol none
modem passthrough nse codec g711ulaw
!
!
!
!
!
!
!
!
!
!

archive
log config
hidekeys
!
!
!
class-map match-any Voice-RTP
match ip dscp ef
match ip rtp 16384 16383
class-map match-any Voice-Cntl
match ip dscp af31
!
!
policy-map QoS-LAN-Policy
class Voice-RTP
set cos 5
class Voice-Cntl
set cos 3
!
!
!
interface FastEthernet0/0
description ### Trunk to EIG LAN ###
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.1
description ### Management VLAN ###
encapsulation dot1Q 1 native
ip address 10.1.2.175 255.255.0.0
!
interface FastEthernet0/0.205
description ### Voice Server VLAN ###
encapsulation dot1Q 205
ip address 10.205.2.175 255.255.0.0
service-policy output QoS-LAN-Policy
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 10.205.1.1
!
no ip http server
!
access-list 30 permit 10.1.5.1
access-list 30 permit 10.200.4.216
snmp-server community E1GpUb73 RO 30
snmp-server community 3I6pR186e RW 30
snmp-server trap-source FastEthernet0/0.1
!
!
control-plane
!
!
!
voice-port 2/0
input gain 14
cptone GB
timeouts ringing infinity
impedance 900r
!
voice-port 2/1
cptone GB
timeouts ringing infinity
!
voice-port 2/2
cptone GB
timeouts ringing infinity
!
voice-port 2/3
cptone GB
timeouts ringing infinity
!
voice-port 2/4
cptone GB
timeouts ringing infinity
!
voice-port 2/5
cptone GB
timeouts ringing infinity
!
voice-port 2/6
cptone GB
timeouts ringing infinity
!
voice-port 2/7
cptone GB
timeouts ringing infinity
!
voice-port 2/8
cptone GB
timeouts ringing infinity
!
voice-port 2/9
cptone GB
timeouts ringing infinity
!
voice-port 2/10
cptone GB
timeouts ringing infinity
!
voice-port 2/11
cptone GB
timeouts ringing infinity
!
voice-port 2/12
cptone GB
timeouts ringing infinity
!
voice-port 2/13
cptone GB
timeouts ringing infinity
!
voice-port 2/14
cptone GB
timeouts ringing infinity
!
voice-port 2/15
cptone GB
timeouts ringing infinity
!
voice-port 2/16
cptone GB
timeouts ringing infinity
!
voice-port 2/17
cptone GB
timeouts ringing infinity
!
voice-port 2/18
cptone GB
timeouts ringing infinity
!
voice-port 2/19
cptone GB
timeouts ringing infinity
!
voice-port 2/20
cptone GB
timeouts ringing infinity
!
voice-port 2/21
cptone GB
timeouts ringing infinity
!
voice-port 2/22
cptone GB
timeouts ringing infinity
!
voice-port 2/23
cptone GB
timeouts ringing infinity
!
!
!
sccp local FastEthernet0/0.205
sccp ccm 10.210.2.1 identifier 1 version 4.1
sccp ccm 10.210.4.1 identifier 2 version 4.1
sccp ccm 10.205.250.1 identifier 3 version 4.1
sccp
!
sccp ccm group 10
associate ccm 2 priority 1
associate ccm 3 priority 2
associate ccm 1 priority 3
!
!
dial-peer voice 200 pots
description ### Dial Peer for Port 2/0 ##
service stcapp
port 2/0
!
dial-peer voice 201 pots
description ### Dial Peer for Port 2/1 ##
service stcapp
port 2/1
!
dial-peer voice 202 pots
description ### Dial Peer for Port 2/2 ##
service stcapp
port 2/2
!
dial-peer voice 203 pots
description ### Dial Peer for Port 2/3 ##
service stcapp
port 2/3
!
dial-peer voice 204 pots
description ### Dial Peer for Port 2/4 ##
service stcapp
port 2/4
!
dial-peer voice 205 pots
description ### Dial Peer for Port 2/5 ##
service stcapp
port 2/5
!
dial-peer voice 206 pots
description ### Dial Peer for Port 2/6 ##
service stcapp
port 2/6
!
dial-peer voice 207 pots
description ### Dial Peer for Port 2/7 ##
service stcapp
port 2/7
!
dial-peer voice 208 pots
description ### Dial Peer for Port 2/8 ##
service stcapp
port 2/8
!
dial-peer voice 209 pots
description ### Dial Peer for Port 2/9 ##
service stcapp
port 2/9
!
dial-peer voice 210 pots
description ### Dial Peer for Port 2/10 ##
service stcapp
port 2/10
!
dial-peer voice 211 pots
description ### Dial Peer for Port 2/11 ##
service stcapp
port 2/11
!
dial-peer voice 212 pots
description ### Dial Peer for Port 2/12 ##
service stcapp
port 2/12
!
dial-peer voice 213 pots
description ### Dial Peer for Port 2/13 ##
service stcapp
port 2/13
!
dial-peer voice 214 pots
description ### Dial Peer for Port 2/14 ##
service stcapp
port 2/14
!
dial-peer voice 215 pots
description ### Dial Peer for Port 2/15 ##
service stcapp
port 2/15
!
dial-peer voice 216 pots
description ### Dial Peer for Port 2/16 ##
service stcapp
port 2/16
!
dial-peer voice 217 pots
description ### Dial Peer for Port 2/17 ##
service stcapp
port 2/17
!
dial-peer voice 218 pots
description ### Dial Peer for Port 2/18 ##
service stcapp
port 2/18
!
dial-peer voice 219 pots
description ### Dial Peer for Port 2/19 ##
service stcapp
port 2/19
!
dial-peer voice 220 pots
description ### Dial Peer for Port 2/20 ##
service stcapp
port 2/20
!
dial-peer voice 221 pots
description ### Dial Peer for Port 2/21 ##
service stcapp
port 2/21
!
dial-peer voice 222 pots
description ### Dial Peer for Port 2/22 ##
service stcapp
port 2/22
!
dial-peer voice 223 pots
description ### Dial Peer for Port 2/23 ##
service stcapp
port 2/23
!
!
!
line con 0
login local
line aux 0
line vty 0 4
login local
!
ntp clock-period 17179905
ntp server 10.1.1.2
end

I found nothing wrong in the config. I checked the IOS which was running on the gateway since they started using it. The IOS was 12.4(15)T5. I decided to do a bug scrub before I further dive into it. A little use of my  googling skills and I found the issue. This particular IOS for VG224 has a well known bug CSCsg85602. The bug description is “DTMF tones not recognised on calls to PSTN from VG224 due to tone leakage”.

This bug was introduced in DSPware 9.4.5 and seems to be causing the problem. I found out that One possible solution was by downgrading the DSPware on the VG224 (while leaving the IOS at 12.4(15)T5 from 9.4.5 to 9.4.4. Then I read about it and realized this has not always resolved the issue.

After going through several release notes I decided to upgrade the IOS to 12.4(15)T13 which was a stable MD release.

Upgarded the IOS and the issue was gone!