H323 Gateway Configuration And Troubleshooting 3a6or

H323 Gateway Configuration and Troubleshooting H323 PROTOCOL:  H.225 -->handles call setup and teardown and q.931 operations.  H.225 RAS(H.245 Feature negotiation (codec negotiation)  H.261/H.263 --Video ission status)--->Handles the gatekeeper conferencing  H.450--Supplementary services (Hold etc)  H323 Fast start(default)-->combining the H.225 and H.245 signalling in a single message.  T.120-->Data Transfer  Video codec --H.261 & H.263  H.245 --Control signalling & Capabilities exchange  H.225 --Call signalling, Registration & RAS control port--1720 Why would we use H323? 1) Widely ed and interoperated(h323 is the default protocol for Cisco) 2) It s Fractional PRI 3) You want caller-id on FXO or T1 CAS-->H323 s whereas MG doest not . Explanation: you are getting an incoming call from PSTN through FXO port on MG gateway and MG Gateway is connected to call manager. The caller id information you will not get when using the MG. 4) PRI Call preservation: When the call agent CUCM goes down then h323 doesn’t not drop call. In case of MG also call will not be dropped but for MG PRI backhaul the calls are dropped. 5) Many call routing and manipulation options 6) s NFAS( Non facility associated signaling): one signaling for multiple PRI lines-Result you will have more channels. 7) H.323 gatekeeper -->Call ission control H.323 configuration Enabling the H.323 service in the Voice Gateway conf t voice service voip h323 no shutdown gateway status show gateway H323 Gateway Addition in call Manager:  H323 and SIP gateway never s with the Call Manager.  Call Manager shows the status of the H323/SIP Gateway as Unknown.

 When adding the H323 Gateway always select the option H323 Gateway in the add Gateway option. For MG Gateway addition you need to select the appropriate model. Cisco CM istration----->device menu--->Gateway--->Add new-->H323 gateway-->device name==>ip-address  Assign the gateway to the Route Pattern for routing the calls to the gateway In the Main menu Call routing--->Route Hunt---> Route pattern-->Add new--> Route Pattern ==> e.g 5001 Gateway/Route list ==> Ip-address of h323 gateway. Configuration of H323 Gateway to communicate with CallManager: Step 1: Create a Loop back interface H323 Gateways do a recursive route table lookup for finding the destination network and use the router closest interface as the source address for commmunicating with the CUCM. H323 bind command ensures the H323 gateway uses the same address every time it communicating with the CUCM. conf t int loopback 0 ip address 192.168.1.19 255.255.255.255 h323-gateway voip interface h323-gateway voip Step 2: To route calls from the H323 Gateway to the CUCM --> Configure atleast one VOIP dialpeer Step 3: Enabling the H323 Service Enters voice-service voip configuration mode Router(config)#voice service voip //This commands will let you to enable H.323 as VoIP service and enters h323 configuration mode Roter(config-voi-serv)#h323 Router(config-serv-h323)#telephony-service ccm-compatible // This command will enable Call Manager compatibility for H323 Step 4: Interaction between the call manager and the H323 Gateway Router# conf t Router(Config)# int fa0/0 Router(config-fa)# ip address 192.168.1.10 255.255.255.0 Router(config-fa)h323-gateway voip interface // This command will bind interface IP Address with H323 for signaling. It used because H323 signaling contains different source address so to make it a single ip address need to bind with interface Router(config-fa)#h323-gateway voip h323-id HVoiceGW1 //Giving the ID HVoiceGW1 to the gateway Router(config-if)#h323-gateway voip bind srcaddr // Assign the ip address of the interface connected to the call manager or the ip address of the Loop back interface Note for H323 gateway

 Fast connect(fast start) -->In a sense, this tunnels H.245 traffic inside H.225 messages-->enabled by default  For call to connect both the end points should the fast start.  The IP phone communicates with its CallManager using Skinny Client Control Protocol (SC). The CallManager exchanges H.323 messages with the H.323 voice gateway using Fast Start.  After creating the h323 gateway in the call manager press the reset button and reset the gateway otherwise it will not work Enable Call survivability on all the VOIP dial-peers on the Router voip service voip h323 call preserve ISSUES FACED IN H323 gateway: 1) Calls not connecting from gateway to another gateway conf t voice service voip allow-connections h323 to h323 allow-connections h323 to sip allow-connections sip to h323 2) SRST issue with H323 gateway: An H.323 gateway exchanges H.225 keepalives with CallManager. To prevent active calls from being terminated when the CallManager becomes unreachable, turn off H.225 keepalives between the gateway and CallManager. GW1(config)#voice service voip GW1(conf-voi-serv)#h323 GW1(conf-serv-h323)#no h225 timeout keepalive 3)Inbound calls not failovering to backup callmanager: Especially if the gateway has a PRI connection for inbound calls. When a call comes in that should be forwarded to a CallManager, the router attempts to set up an H.225 T session to its preferred VoIP dial peer. The T session must time out before it will try another dial peer. This takes 30 seconds by default. ISDN Q.931 has a Call Proceeding timeout of 10 seconds. A call that comes in over a PRI line will time out before the router can fail over to an alternate CallManager. Even without a PRI connection, 15 seconds might be longer than you want to wait. To remedy this, change the H.225 T session establishment timer. The voice class h323 10 command creates a voice class in global configuration mode that reduces the timer to three seconds: NYCgateway(config)#voice class h323 10 NYCgateway(configs-class)#h225 timeout t establish 3

4) Calls are Dropped When the call manager Fails then H323 Gateway is configured for SRST--->H323 gateway drops the active calls. When the Call Manager comes online again the calls are droppped. CUBE (Cisco border element has no effect by enabling the no h225 timeout keepalive)-->IP to IP calls will be traversing the CUBE voice service voip no h225 timeout keepalive ---> disabels the keepalive messages. voice class h323 1 h225 timeout t establish 2 h225 timeout setup 2 call preserve H323 Gateway Failover Configuration Cisco IOS gateways also handle Cisco CallManager failover situations. By using several enhancements to the dial-peer and voice class commands in Cisco IOS Release 12.1(2)T, Cisco IOS gateways can redundant Cisco CallManagers. The command, h225 t timeout seconds, specifies the time that it takes for the Cisco IOS gateway to establish an H.225 control connection for H.323 call setup. The following example shows the configuration for H.323 gateway failover: interface FastEthernet0/0 ip address 10.1.1.10 255.255.255.0 --->10.1.1.10 (Ip address of CUCM) voice class h323 1 h225 timeout t establish 3 h225 timout setup 2 dial-peer voice 101 voip destination-pattern 1111 session target ipv4:10.1.1.101 preference 0 ---->Preference 0 (This is the primary route for connecting with CUCM) voice class h323 1 dial-peer voice 102 voip destination-pattern 1111 session target ipv4:10.1.1.102 preference 1 ---->(Backup route) voice class h323 1 h225 timeout t establish 3 -->If the H323 Gateway cannot establish a T connection with CUCM within 3 seconds then it will try the next dial-peer with inferior preference. h225 timeout t setup 2 --> The H.225 setup message is sent to the CUCM and the CUCM is not responding for the setup message within 2 seconds then next dial-peer with inferior preference is used. H.225 message is sent after establishment of T connection.

H323 Gateway Status Verification  show h323 gateway  clear h323 gateway --clears the statistics  show debug --->command to display the debug commands applied  show dial-peer voice summary --->shows the summary of the dial peers  show dialplan number 9790523431 --->shows which dial peers are matched.  csim start phone-number command--->You can simulate a phone call from the router Debugging a H323 Call:  debug cch323 h225 and debug cch323 h245 -->call setup and tear down checking.  debug voip dialpeer --->good one for troubleshooting  debug ip t transaction ----> to make sure that the T session for H.225 and H.245 is being established. Other configurations on H323:  call service stop --->Stops the h323 call processing  The faststart is enabled by default call start slow ---> disable the h323 faststart.