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Some, not all, calls fail to connect when routed interzone through an IOS H323 gatekeeper

Core Issue

These are the symptoms of the issue:

  • The local gatekeeper is expected to route calls to more than one local zone or is expected to route calls to gatekeepers in remote zones.
  • Calls within a local zone can be routed successfully.
  • Some interzone calls can be routed successfully.
  • Interzone calls not routed successfully are called numbers with a specific number of digits. For example, calls to a 10-digit or 9-digit number may succeed, while a call to a 3-digit number starting with the same digit reliably fails.
  • The gatekeeper configuration makes use of dot wildcards within zone prefixes.

Resolution

When specifying wildcard digits within a zone prefix, avoid the use of dots where possible. Instead, use the less specific asterisk wildcard.

To resolve this issue, choose from one of these options:

  • If the dial plan is consistent, you can use a configuration with only dots or only asterisks.        
  • If there is an overlap in the dial plan, stick to using configurations with asterisks.        
  • If there is an overlap in the dial plan and a configuration with only asterisks is not suitable, study the gatekeeper's default behavior of prefix guessing. This consists of deducing and prepending the local area code to the called number. This should be done before configuring the gatekeeper. 

For information on the gatekeeper's behavior, refer to Zone Prefix Processing with Dots Versus Asterisks.

Usually the called number is prepended with the calling number's local area code. This altered number then matches a local zone prefix and cannot be routed.

Test a resolution to this issue by removing the matching local zone prefix or changing it to use the dot wildcard.

For more information on gatekeeper call routing, refer to Understanding Cisco IOS H.323 Gatekeeper Call Routing.

Gatekeeper Configuration

Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 05:38 PM
Updated by: