c8fa26c0_Internal_Error_Codes___DocWiki__Descriptor
[Code] 28 [Explanation] An incoming call setup indication was received, bearing the same globally unique identifier (GUID) as a call in existence. The call is being rejected because a loop is suspected. [Category] 180 [Descriptor] 
Incoming loop
Cisco IOS Voice Troubleshooting and Monitoring -- Cisco VoIP Internal Error Codes - DocWiki
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