Cable Modem Voice Configuration Using H323v2 Dynamic Mapping with Gatekeeper

Document ID: 12190

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Configure
      Network Diagram
      Configurations
Verify
Troubleshoot
      Troubleshooting Commands
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Related Information

Introduction

This is a sample configuration for Voice over IP (VoIP) between two cable modems connected through the same Cable Modem Terminal Server (CMTS). The call is established end-to-end and does not go through through the Public Switched Telephone Network (PSTN). The cable modems are configured in bridging mode. However, they are equally configured for routing mode without any change in the VoIP configurations. This document provides a basic VoIP setup in a lab environment with the use of Dynamic Mapping Configuration.

Note: When the cable modem router acts in DOCSIS-bridging mode, a voice call that originates from the Ethernet interface of the router does not terminate on another device attached to that same Ethernet interface. It terminates on a device that is reached through the cable interface. In order to allow calls to both originate and terminate on the Ethernet interface, the router is configured in routing mode.

The Dynamic Mapping Feature requires the presence of a gatekeeper. When you use H.323v2, a VoIP supported Cisco uBR9xx or a CVA122 acts as an H.323v2 gateway that forwards the voice packets to the CMTS. It then sends them to a Telephony gatekeeper. The gatekeeper transmits the packets to their ultimate destination. The gateway at the destination interconnects the IP network to the PSTN so that calls can be made to any phone, not just those that are part of the IP Telephony network.

A protocol called Registration, Admission, and Status (RAS) is used between the gateway, in this case the cable modem router, and the gatekeeper. This allows the gateway to register the E.164 addresses with the gatekeeper. The gatekeeper maintains a central database of dial peers, so that this information does not have to be entered into static dial maps on every cable modem router that is acting as a voice gateway. This simplifies the configuration task.

A Cisco 3600 or 2600 series router is used as a gatekeeper when you run Cisco IOS® Software that supports the gatekeeper functionality.

Note: Support for RAS and H.323v2 in Cisco gatekeeper products is found in Cisco IOS Software Release 12.0(5)T or later. An IOS that supports the gatekeeper functionality is identified by the 'IX' symbol in the image name, for example c3660-ix-mz.121-7.

Voice signals are packetized and transported in compliance with these protocols:

H.323v2—The second version of an International Telecommunications Union (ITU) standard that specifies call signaling and control protocols for an IP data network. This is supported on Cisco IOS Software Release 12.0(4)XI and later voice images.
Simple Gateway Control Protocol (SGCP) Version 1.1—A signaling protocol under review by the Internet Engineering Task Force (IETF). This is supported on Cisco IOS Software Release 12.0(7)T and later voice images.
Media Gateway Control Protocol (MGCP) Version 0.1—A proposed IETF voice control protocol intended to eventually supersede the existing SCGP 1.1 protocol. This is supported on Cisco IOS Software Release 12.1(3)T and later voice images.

Note: When you use SGCP or MGCP, the Cisco Cable Modem router acts as the residential gateway that forwards the voice packets to the CMTS. It then connects to the external call agent (SGCP or MGCP) or media gateway controller (MGCP). The call agent or controller determines how to transmit the call across the network to the trunking gateway that is its ultimate destination.

In this setup the H.323v2 protocol is used. For more on H.323, refer to H.323 Version 2 Support.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

Two cable modem routers that use uBR924 series routers that run Cisco IOS Software Release 12.1(5)T.
A CMTS that use a uBR7223 that runs Cisco IOS Software Release 12.1(5)T.
Cisco 3660 that runs Cisco IOS Software Release 12.1(7) that acts as a gatekeeper.
Two analog phones each connected to the v1+v2 ports on the uBR924.
Cisco Network Registrar (CNR) that act as DHCP, TFTP, and severs. In the same server, Time of Day (ToD) is running.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to Cisco Technical Tips Conventions.

Configure

This section presents you with the information you can use in order to configure the features this document describes.

Note: In order to find additional information on the commands this document uses, use the Command Lookup Tool ( registered customers only) .

Network Diagram

This document uses the network setup shown in this diagram:

Configurations

These are the configurations for both the cable modems, CMTS, and the gatekeeper.

Psyduck (uBR924)
Raichu (uBR924)
Sniper (CMTS)
3660 ( Gatekeeper )

Psyduck (uBR924)

Psyduck#write terminal       
Building configuration...

Current configuration : 1452 bytes
!
! Last configuration change at 14:48:20 - Mon Mar 5 2001
! NVRAM config last updated at 14:49:18 - Mon Mar 5 2001
!
version 12.1
no service single-slot-reload-enable
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Psyduck
!
logging rate-limit console 10 except errors
enable password cisco
!
clock timezone - 0
ip subnet-zero
no ip routing
no ip finger
no ip domain-lookup
!         
ip audit notify log
ip audit po max-events 100
call rsvp-sync

!
interface Ethernet0
 ip address 10.50.50.2 255.255.255.0
 no ip route-cache
 no ip mroute-cache
 bridge-group 59
 bridge-group 59 spanning-disabled
!
interface cable-modem0
 ip address docsis
 no ip route-cache
 no ip mroute-cache
 bridge-group 59
 bridge-group 59 spanning-disabled
 h323-gateway voip interface        
 
!--- Cable interface is the H.323 gateway VoIP interface.

 h323-gateway voip id 3660-gk ipaddr 172.17.110.145 1718 
 
!--- Gatekeeper ID and IP address/port.

 h323-gateway voip h323-id ubr1     
 
!--- Specify the H.323 ID for this interface. 
 !--- This ID is any string that uniquely
 !--- identifies this gateway to the gatekeeper.

!
ip default-gateway 10.50.50.1
ip classless
no ip http server
no ip http cable-monitor
!
snmp-server packetsize 4096
snmp-server manager
!
voice-port 0
 input gain -2
!
voice-port 1
 input gain -2
!
dial-peer voice 1 pots             
 destination-pattern 1111           
 
!--- Local phone number. Remote cable modem calls this number..

 port 0
!
dial-peer voice 10 voip           
 destination-pattern 3...          
 
!--- VoIP, any destination phone number that starts
 !--- with 3 followed by any three digits.

 session target ras                
 
!--- Send to the gatekeeper.

!
gateway                            

!--- Enable the VoIP gateway on this router.

!
!
line con 0
 exec-timeout 0 0
 transport input none
line vty 0
 exec-timeout 0 0
 password cisco
 no login
line vty 1 4
 password cisco
 no login
!
end

Raichu (uBR924)

Raichu#write terminal
Building configuration...

Current configuration : 1235 bytes
!
! Last configuration change at 14:46:25 - Mon Mar 5 2001
! NVRAM config last updated at 14:49:32 - Mon Mar 5 2001
!
version 12.1
no service single-slot-reload-enable
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Raichu
!
logging rate-limit console 10 except errors
!
clock timezone - 0
ip subnet-zero
no ip routing
no ip finger
!
ip audit notify log
ip audit po max-events 100
call rsvp-sync
!

interface Ethernet0
 ip address 10.50.50.5 255.255.255.0
 no ip route-cache
 bridge-group 59
 bridge-group 59 spanning-disabled
!
interface cable-modem0
 ip address docsis
 no ip route-cache
 no ip mroute-cache
 bridge-group 59
 bridge-group 59 spanning-disabled
 h323-gateway voip interface                 
 
!--- Cable interface is the H.323 gateway VoIP interface.

 h323-gateway voip id 3660-gk ipaddr 172.17.110.145 1718   
 
!--- Gatekeeper ID and IP address/port.

 h323-gateway voip h323-id ubr2              
 
!--- Specify the H.323 ID for this interface. 
 !--- This ID is any string that uniquely
 !--- identifies this gateway to the gatekeeper.

!
ip classless
no ip http server
no ip http cable-monitor
!
snmp-server packetsize 4096
snmp-server manager
!
voice-port 0
 input gain -2
!
voice-port 1
 input gain -2
!
dial-peer voice 3 pots              
 destination-pattern 3333                  
 
!--- Local phone number. Remote cable modem calls this number.

 port 0
!
dial-peer voice 30 voip
 destination-pattern 1...                  
 
!--- VoIP, any destination phone number that starts 
 !--- with 1 followed by any three digits.

 session target ras                        
 
!--- Send to the gatekeeper.

!
gateway                                    

!--- Enable the VoIP gateway on this router.

!
!
line con 0
 transport input none
line vty 0 4
!
end

Raichu#

Sniper (CMTS)

Sniper#

Building configuration...

Current configuration : 2389 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
service udp-small-servers max-servers no-limit
!
hostname Sniper
!
boot system flash slot0:ubr7200-ik1st-mz.121-5.T.bin
logging rate-limit console 10 except errors
enable password cisco
!
no cable qos permission create
no cable qos permission update
cable qos permission modems
cable time-server
ip subnet-zero
no ip finger
no ip domain-lookup
!         

interface FastEthernet0/0
 description Connection to lab backbone
 ip address 172.17.110.148 255.255.255.224
 half-duplex
!
interface Ethernet1/0
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/1
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/2
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/3
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/4
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/5
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/6
 no ip address
 shutdown
 half-duplex
!
interface Ethernet1/7
 no ip address
 shutdown
 half-duplex
!
interface Cable2/0
 ip address 192.168.50.1 255.255.255.0 secondary
 ip address 10.50.50.1 255.255.255.0
 no keepalive
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable downstream frequency 555000000
 cable upstream 0 frequency 30000000
 cable upstream 0 power-level 0
 no cable upstream 0 shutdown
 cable upstream 1 shutdown
 cable upstream 2 shutdown
 cable upstream 3 shutdown
 cable upstream 4 shutdown
 cable upstream 5 shutdown
 cable dhcp-giaddr policy
 cable helper-address 172.17.110.137          
 
!--- IP address of Cisco Network 
 !--- Registrar (DHCP, TFTP and ToD servers).

!
interface Cable3/0
 no ip address
 no keepalive
 shutdown
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable upstream 0 shutdown
 cable upstream 1 shutdown
 cable upstream 2 shutdown
 cable upstream 3 shutdown
 cable upstream 4 shutdown
 cable upstream 5 shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 172.17.110.129
no ip http server
!
line con 0
 exec-timeout 0 0
 transport input none
line aux 0
line vty 0 4
 exec-timeout 0 0
 no login
!
end

3660 ( Gatekeeper )

LandRover#write terminal
Building configuration...

Current configuration : 651 bytes
!
version 12.1
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname LandRover
!
boot system flash c3660-ix-mz.121-7

!
ip subnet-zero
no ip finger

!         
interface FastEthernet0/0
 ip address 172.17.110.145 255.255.255.224
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
ip classless
ip route 0.0.0.0 0.0.0.0 172.17.110.148
no ip http server
!
!
gatekeeper
 zone local 3660-gk cisco.com 172.17.110.145       
 
!--- Gatekeeper name, domain name, and IP address.

 zone prefix 3660-gk *                             
 
!--- E.164 address prefix managed by the specified gatekeeper.

 no shutdown
!
!
line con 0
 exec-timeout 0 0
 transport input none
line aux 0
line vty 0 4
 login
!
end

LandRover#

Verify

This section provides information to confirm that the configuration works properly.

Certain show commands are supported by the Output Interpreter Tool ( registered customers only) . This allows you to view an analysis of show command output.

show dial-peer voice summary—Displays a short summary of each voice dial peer.
show call active voice brief—Displays a truncated version of call information for voice calls in progress.
show gateway—Displays the current status of the gateway.
show voice port x—Displays configuration information about a specific voice port.
show dialplan number ###—Displays which outgoing dial peer is reached when a particular telephone number is dialed.
show gatekeeper calls—Displays the status of each ongoing call about which a gatekeeper is aware.
show gatekeeper endpoints—Displays the status of all registered endpoints for a gatekeeper.
show gatekeeper status—Displays the overall gatekeeper status. This includes authorization and authentication status and zone status.
show gatekeeper zone status—Displays the status of zones related to a gatekeeper.

On the uBR924:

Raichu#show dial-peer voice summary 
dial-peer hunt 0
                                                      PASS
  TAG TYPE   ADMIN OPER PREFIX   DEST-PATTERN    PREF THRU SESS-TARGET    PORT
    3 pots   up    up            3333             0                       0
   30 voip   up    up            1...             0   syst ras                 
Raichu#

Another useful command is show call active voice brief. At the bottom of the display, look for Total call-legs. Here is an example of the lower portion of the output. The details are highlighted here:

Total call-legs: 2
7    : 96377hs.1 +542 pid:3 Answer 3333 active
 dur 00:07:41 tx:23148/462931 rx:23102/461992
 Tele 0:3: tx:462990/462020/0ms g729r8 noise:-53 acom:0  i/0:-36/-41 dBm

7    : 96640hs.1 +278 pid:30 Originate 1111 active
 dur 00:07:42 tx:23080/461552 rx:23222/464411
 IP 10.50.50.2:0 rtt:12ms pl:459520/720ms lost:0/11/42 delay:34/34/194ms g729r8

If calls are not established, check to see if the gateway is registered with the gatekeeper:

Raichu#show gateway 
 Gateway  ubr2  is registered to Gatekeeper 3660-gk

Alias list (CLI configured) 
 E164-ID 3333
 H323-ID ubr2
Alias list (last RCF) 
 E164-ID 3333
 H323-ID ubr2

 H323 resource thresholding is Disabled
Raichu#

More commands:

show voice port x 
show dialplan number ###

Commands to be used on the gatekeeper:

LandRover#show gatekeeper calls 
Total number of active calls = 1.
                         GATEKEEPER CALL INFO
                         ====================
LocalCallID                        Age(secs)   BW
9-60916                            1289        64(Kbps)
 Endpt(s): Alias        E.164Addr     CallSignalAddr  Port  RASSignalAddr   Port
   src EP: ubr2         3333          10.50.50.5      1720  10.50.50.5      5703
   dst EP: ubr1         1111          10.50.50.2      1720  10.50.50.2      5683
LandRover#show gatekeeper endpoints 
                    GATEKEEPER ENDPOINT REGISTRATION
                    ================================
CallSignalAddr  Port  RASSignalAddr   Port  Zone Name         Type    F 
--------------- ----- --------------- ----- ---------         ----    --
10.50.50.2      1720  10.50.50.2      56893 3660-gk           VOIP-GW  
    E164-ID: 1111
    H323-ID: ubr1
10.50.50.5      1720  10.50.50.5      57083 3660-gk           VOIP-GW  
    E164-ID: 3333
    H323-ID: ubr2
Total number of active registrations = 2


LandRover#show gatekeeper status 
    Gatekeeper State: UP
    Zone Name:        3660-gk
    Accounting:       DISABLED
    Security:         DISABLED
LandRover#show gatekeeper zone status 
                         GATEKEEPER ZONES
                         ================
GK name      Domain Name   RAS Address     PORT  FLAGS MAX-BW   CUR-BW
                                                       (kbps)   (kbps)
-------      -----------   -----------     ----  ----- ------   ------
3660-gk      cisco.com     172.17.110.145  1719  LS             64      
  SUBNET ATTRIBUTES :
    All Other Subnets : (Enabled)
  PROXY USAGE CONFIGURATION :
    Inbound Calls from all other zones : 
      to terminals in local zone 3660-gk : use proxy
      to gateways in local zone 3660-gk  : do not use proxy
    Outbound Calls to all other zones :
      from terminals in local zone 3660-gk : use proxy
      from gateways in local zone 3660-gk  : do not use proxy

On the CMTS:

Sniper#show cable modem
Interface   Prim Online     Timing Rec    QoS CPE IP address      MAC address
            Sid  State      Offset Power
Cable2/0/U0 1    online     2291   -0.50  5   0   10.50.50.4      0050.7366.2223
Cable2/0/U0 2    online     2812   -1.00  5   0   10.50.50.5      0001.9659.4449
Cable2/0/U0 3    online     2813    0.25  5   0   10.50.50.2      0001.9659.4477

Sniper#

Troubleshoot

This section provides information to troubleshoot the configuration.

Troubleshooting Commands

Certain show commands are supported by the Output Interpreter Tool ( registered customers only) . This allows you to view an analysis of show command output.

Note: Before you issue the debug commands, refer to Important Information on Debug Commands.

The most commonly used debug commands for VoIP are:

debug voip ccapi inout—Traces the execution path through the call control application programming interface (API).
debug cch323 h225—Traces the state transition of the H.225 state machine based on the processed event.
debug cch323 h245—Traces the state transition of the H.245 state machine based on the processed events.

For more information, refer to Verify End-to-End VoIP Signaling (VOIP Call-Leg).

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Updated: Oct 11, 2005

Document ID: 12190

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