Call Manager does not recognise E1 link loss from H323 Gateway

Answered Question
Oct 17th, 2007

My Customer is running Call Manager version 3.3(5) and has 4 1700 series routers each with 1 E1 circuit configured as H323 gateways. Last week when the carrier's circuit on the first choice gateway went down; (loss of layer 1); outgoing PSTN calls did not route out of the second choice gateway in the route list. I believe this is due to the fact that these gateways are configured at H323 gateways and there is no signal between the gateway and Call Manager to indicate the loss of E1, whereas if they had been configured as MGCP gateways, the Call Manager would have detected this and routed all subsequent calls out of the 2nd gateway in the list. Am I right?

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Correct Answer by nomiel about 9 years 1 month ago

Hi, by default Callmanager stops routing on Unallocated number message from gateway, so if E1 is down, it receives this message and tells that number is unavailable. In order to make callmanager to go through second gateway in route list just set Callmanager Service Parameter "Stop Routing on Unallocated Number Flag" to "False".

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Correct Answer
nomiel Wed, 10/17/2007 - 03:08

Hi, by default Callmanager stops routing on Unallocated number message from gateway, so if E1 is down, it receives this message and tells that number is unavailable. In order to make callmanager to go through second gateway in route list just set Callmanager Service Parameter "Stop Routing on Unallocated Number Flag" to "False".

Peter Bishop Wed, 10/17/2007 - 03:22

Hi, is this parameter for intercluster tunks rather than gateways? The dialled number for a PSTN call is '9' so is not an unallocated number. This is the 'help' text that appears when you click the parameter option:-

This parameter determines routing behavior for intercluster trunk calls to an unallocated number. An unallocated number is a dialed directory number that does not exist in a Cisco cluster. Valid values specifyTrue or False. When the parameter is set to True and a call being routed to a remote Cisco cluster through a route list is released by a remote Cisco CallManager because of the unallocated number, a local Cisco CallManager will stop routing the call to the next device in the route list. When the parameter is set to False, the local Cisco CallManager will route the call to the next device.

This is a required field.

Default: true.

nomiel Wed, 10/17/2007 - 03:30

No, not only intercluster trunk, but every "Unallocated/unknown number" messages. If e1/t1 channel is down then isdn sends this message.

shane.orr Wed, 10/17/2007 - 03:54

Does anyone know if this applies only to H323 T1/E1 or will H323 Gateway with FXO also hunt to the next member in the route list in call manager? My gut feeling is that it will not because it does not work the same.

jonesbrett Fri, 10/19/2007 - 09:59

You can also create another VOIP dialpeer on router 1-3 as follows:

ip host SUGW02 172.31.X.X (router 2)

dial-peer voice 901 voip

description Backup for local PRI failure

preference 1

destination-pattern 9T

progress_ind setup enable 3

modem passthrough nse codec g711ulaw

voice-class codec 1000

voice-class h323 1

session target dns:SUGW02

dtmf-relay h245-alphanumeric

When an outbound call is made the router will match on the destination pattern of 9T and then preference. As your POTS dialpeer should not have the preference statement in it, it will be first dialpeer matched. If the call fails it will search for the next dailpeer with a destination of 9T and with a preference of 1 (or higher) which will forward call to the next router.

You can create additional dialpeers to point to router 3 and 4.

Peter Bishop Mon, 11/19/2007 - 07:35

Hi,

only managed to change this on Friday, but we tried taking links down and everything re-routed onto the next gateway. Thanks for your help. I have rated your original reply!

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