H.323 Configuration

H.323 Elements:
- H.245 - codecs and features negotiation
- H.225 - call setup
- H.225 RAS - gatekeeper (Registration, Admition, Status)

H.323 Basic Call Flow:
Configuration:

! Enable h323 VOIP servises
Router(config)#voice service voip
Router(conf-voi-serv)#h323
! specifies the time to maintain an established H.225 TCP connection when there are no calls on that connection
Router(conf-serv-h323)#h225 timeout tcp call-idle never
!
Router(config)#interface loopback 0
Router(config-if)#ip address 10.10.1.1 255.255.255.0
Router(config-if)#h323-gateway voip interface
Router(config-if)#h323-gateway voip h323-id gw1
Router(config-if)#h323-gateway voip bind srcaddr 10.10.1.1
! Codecs configuration
Router(config)#voice class codec 100
Router(config-class)#codec preference 1 g711alaw
Router(config-class)#codec preference 2 g729br8
!
Router(config)#voice class h323 600
! TCP establish timeout value in seconds. Default: 15
Router(config-class)#h225 timeout tcp establish 10
! sets the timeout value, in seconds, for the response of the outgoing SETUP message. Default: 15
Router(config-class)#h225 timeout setup 10
!
Router(config)#dial-peer voice 500 voip
Router(config-dial-peer)#voice-class codec 100
Router(config-dial-peer)#voice-class h323 600
Router(config-dial-peer)#dtmf-relay {[cisco-rtp] [h245-alphanumeric] [h245-signal] [rtp-nte [digit-drop]] [sip-notify]}

Fax Pass-Through (G.711, No VAD, No Echo Cancelation):
Router(config)voice service voip
Router(config-serv)#fax protocol pass-through
or
Router(config)#dial-peer voice 50 voip
Router(config-dial-peer)#destination-pattern 50
Router(config-dial-peer)#session target ipv4:10.10.10.50
Router(config-dial-peer)fax protocol pass-through g711alaw
Router(config-dial-peer)#fax rate 14400

Fax T.38 Relay:
Router(config)#voice service voip
Router(conf-voi-serv)#fax protocol {t38|cisco}
!
Router(config)#dial-peer voice 51 voip
Router(config-dial-peer)#destination-pattern 51
Router(config-dial-peer)#session target ipv4:10.10.10.50
! Disable fax-relay Error Correction Mode
Router(config-dial-peer)#fax-relay ecm disable
! Enable the fax stream between two SG3 fax machines to negotiate down to G3 speeds
Router(config-dial-peer)#fax-relay sg3-to-g3
Router(config-dial-peer)#fax rate 14400

DTMF Relay:
Router(config-dial-peer)#dtmf-relay h245-alphanumeric

Verifying Configuration:
#show gateway
#debug cch323 h225
#debug cch323 h245
#debug h225
#debug h245
#debug voip ccapi inout