4f55f5cb_ISDN_Cause_Codes__Cause_Usage
[Cause#] 2 [Fixit!] N/A [Cause Summary] No route to specified transit network. [Cause Usage] 
Indicates that the equipment sending this cause has received a request to route the call through a particular transit network which it does not recognize. The equipment sending this cause does not recognize the transit network either because the transit network does not exist or because that particular network, while it does exist, does not serve the equipment which is sending the cause.
ISDN Cause Codes
Cause Usage