Top and Most useful Cisco Voice IOS Commands

If you are working as a Voice Engineer or planning to learn Voice or may have an interview, the below list of commands are the ones which are most commonly used by Voice Engineers. These commands are posted here so that it can be helpful for everyone who are troubleshooting/learning the voice piece or may want to use this topic as a reference to their daily work. I might have missed some commands which you can post me in the comment so that i can add them as well.

Show cdp – It will show CDP Timer and Holdtime Frequency
Show cdp neighbors detail – It will show details of neighbor with an IP Address and IOS version
Show cdp neighbors – It will show details of Device ID, Local Interface, Holdtime, Capability, Platform and Port ID
Show cdp interface – It will show details of the interface if it is Up physically, Line protocol is up, Encapsulation and Holdtime.
Show cdp traffic – It will show details of the CDP counters (CDP packets sent and received)
Show voice call summary – It will show all the active calls on the Gateway, Ports, Codec, VAD (enabled or not), VTSP state and VPM state
Show voice call status – It will show only the active calls, not all the ports. It includes Port, Called Number, and Dial Peer
Show call history voice record – It will show information about calls made to and from the voice router
Show voice port summary – It will show a detailed information on Ports, Channel, Signalling Type, Port Status, In Operation Status, Out Status and EC. It basically shows FXO/FXS/PRI ports in use.
Show gateway – It will show the state and version is H.323
Show dialplan number 1000 – It will show you what happens when the specified number is dialed
Show dial-peer voice summary – It will show you what all dial-peers that are currently working. Summary of dial-peers/destination.
Show voip rtp connections  – It will show all the current RTP connections which will have Local and Remote IP Address, Port Numbers, Call IDs.
show controllers T1    or   show controllers E1 – It will show the status of a controller if it is up or down
show call active voice brief – It will show the active call information which includes Call ID, Peer IP Address and Codecs
Show mgcp  – It will show mgcp settings on the gateway
Show dial-peer voice – It will show how voice dial peers are configured.
Show mgcp statistics  – It will show mgcp statistics relationship between the devices which will have stats for CRCX, DLCX, MDCX and RSIP,  IP addresses of Call Agents etc
Show mgcp endpoint –  It will show information related to MGCP endpoints
Show mgcp connection  – It will show information about the current mgcp connections
show sip-ua register status – It will show SIP Registration information
show voice dsp – It will show the status of all the DSPs on the Gateway
show ccm-manager  – It will show information about the active and redundant configured Cisco Unified Communications Manager. This command also indicates if the gateway is currently registered with Cisco Unified Communications Manager.
Show isdn active – It will show if a call is in progress and which number is being dialed.
Show isdn status – It will show statistics of an ISDN connection and show if your PRI is up/established correctly
show ccm-manager fallback – It will show whether MGCP fallback is enabled or disabled, if enabled, whether it is currently active or not.
Show sip service – It will help to display the status of SIP call service in a SIP gateway
show sip-ua status – It will help to display status for the SIP user agent (UA), including whether call redirection is enabled or disabled
cdp enable – It will enabled CDP on an interface
no cdp enable – It will disable CDP on an interface
Test voice translation-rule – It will allow you to test a translation rule configured on the gateway.
Csim start XXXXX – It is a hidden command which helps to generate calls
Debug voice ccapi inout – It will show calls in and out of ports on the gateway
Debug mgcp packet  – It will monitor the packets exchanged between CUCM and router.
Debug isdn q921 – It will help to verify if you have a connection to the ISDN switch.
Debug isdn q931  – It will monitor information about call setup and tear down of ISDN network connections (layer 3) between local router (user side) and the network
Debug h225  – It will display additional information about the contents of H.225 Registration, Admission, and Status Protocol (RAS) messages.
Debug vtsp tone – It will help to view tone generated by the router which could be fast busy or dial tone or busy signal etc.
Debug voip ccapi inout – It will trace the execution path through the call control API, which serves as the interface between the call session application and the underlying network-specific software.
Debug vpm signal – It will help to view to view the on−hook and off−hook signaling for the voice ports.
Debug vtsp dsp  – It will help to view digits collection performed on the router
Debug ccsip calls – It will help to show all SIP call details as they are updated in the SIP call control block. This debug command can be used to monitor call records for suspicious clearing causes.
Debug ccsip messages – It will help you to enable all SIP message tracing, such as those that are exchanged between the SIP user-agent client (UAC) and the access server
Debug isdn event – It will show events occurring on the user side (on the router) of the ISDN interface. The ISDN events that can be displayed are Q.931 events (call setup and teardown of ISDN network connections)

All the best!

Avinash Karnani

I am working in an IT company and having 10+ years of experience into Cisco IP Telephony and Contact Center. I have worked on products like CUCM, CUC, UCCX, CME/CUE, IM&P, Voice Gateways, VG224, Gatekeepers, Attendant Console, Expressway, Mediasense, Asterisk, Microsoft Teams, Zoom etc. I am not an expert but i keep exploring whenever and wherever i can and share whatever i know. You can visit my LinkedIn profile by clicking on the icon below.

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