Scenario#27 – RightFax Server not working – MGCP

I had an interesting scenario where customer logged a case with us regarding their RightFax server not working. Those of you who don’t know what is a RightFax server can read about it here. When you dial the fax number from outside, it reaches the gateway and you hear one ringback and then a fast busy. The call flow was something like this: 0XXXX23422 >>>> Birmingham GW  FXO >>> on CCM we have FXO port with number 3422 >> on CCM there was a RP 3422 with a RL pointing towards an Intercluster trunk to 192.168.10.39. The 192.168.10.39 was the … Continue reading Scenario#27 – RightFax Server not working – MGCP

Scenario#24 – SIP Calls drop after Silence

Came across a complex situation where customer was using this SIP trunk as an alternative to ISDN-30 (if all channels are used or if ISDN goes down). The ISDN-30 link was working fine but they had issues on SIP trunk (how many times I have heard this?) …. their outbound calls over SIP were using a prefix ‘8’ to route calls on SIP trunk to SIP Provider. The Outbound calls were working fine. The inbound calls drop after 8 secs and none of the calling/called party could hear each other. Complete silence.. Call flow was something like this: PSTN (81763)  … Continue reading Scenario#24 – SIP Calls drop after Silence

DSP, PVDM & Media Resources

The Cisco High-Density Packet Voice Digital Signal Processor (DSP) Module (PVDM2) enables Cisco Integrated Services Routers to provide high-density voice connectivity, conferencing, and transcoding capabilities in Cisco IP Communications solutions. PVDM stands for packet voice DSP module; it is the Cisco product name for the module that provides digital signal processing resources to a system. DSP stands for Digital Signal Processor; it is a generic Industry terminology. A PVDM module could be staffed with one or multiple DSPs. PVDM2-8 = 8ch (G), 4ch (H), 4ch (M) PVDM2-16 = 16ch (G), 6ch (H), 8ch (M) PVDM2-32 = 32ch (G), 12ch (H), … Continue reading DSP, PVDM & Media Resources

Scenario#23 – Fax Issues for ATA

Fax machines connected to ATA were not working. The first thing I checked on the gateway…is fax-relay was being used or fax protocol cisco was configured? Fax-relay is NOT supported by ATA. This is what I found at the Voice gateway: voice service voip allow-connections h323 to sip allow-connections sip to h323 allow-connections sip to sip supplementary-service h450.12 fax protocol cisco I found the reason why faxes were not working. Fax protocol cisco was used which enabled default fax-relay. I configured the following: voice service voip fax protocol none {or could have configured modem passthrough nse codec g711ulaw} dial-peer voice … Continue reading Scenario#23 – Fax Issues for ATA

IOS 15.1 Toll Fraud feature

A new feature has been introduced in Cisco IOS® Software Release 15.1(2)T to guard against the incidence of toll-fraud on Voice GateWays (VGWs) installed with Cisco IOS. Starting with IOS 15.1(2)T and newer releases of IOS based on this version, the toll-fraud prevention settings are the default behavior of Cisco IOS-based VGWs. Behavior Before 15.1(2)T For all IOS releases before 15.1(2)T, the default behavior for IOS voice gateways is to accept call setups from all sources. As long as voice services are running on the router, the default configuration will treat a call setup from any source IP address as … Continue reading IOS 15.1 Toll Fraud feature

Scenario#22 – ISDN user busy 0x8091

This was an interesting scenario where incoming calls were getting ‘user busy’ message at the gateway and an engage tone was heard at calling party side. *Aug 18 08:36:53.581: ISDN Se0/0/0:15 Q931: RX <-CALL_PROC pd = 8  callref = 0x8D7E Channel ID i = 0xA9839E Exclusive, Channel 30 *Aug 18 08:36:54.997: ISDN Se0/0/0:15 Q931: RX <- DISCONNECT pd = 8  callref = 0x8D7E Cause i = 0x8091 -User busy It was not just one extension but several extensions which were having the same issue. They were all running fine till yesterday! Something must have happened… I did debug voip ccapi … Continue reading Scenario#22 – ISDN user busy 0x8091

Scanario#21 – VG224 Fax Issues

Customer reported a fault that several fax machines which were working fine last week have suddenly stopped working. All they were getting for incoming faxes was just the header. No content of the actual fax. Rule of thumb – anything which was working before and not working now means something must have changed. I jumped on the main Voice gateway which was connected to the switch and the Fax machines were connected to the VG224. A typical depiction could be as follows: PSTN >> VGW >> SW >> VG224 >> FAX There were 3x E1 cards on the Voice gateway. … Continue reading Scanario#21 – VG224 Fax Issues