Call routing failures are often caused by which scenario?

• A. CSS/partition mismatch
• B. All of the above
• C. Missing route patterns
• D. Trunk/gateway down

Answer: (B)

Call routing relies on a correctly configured dial plan, where access control, available routes, and the signaling path all line up. If the Calling Search Space and partitions don’t grant access to the destination’s route pattern, the call can be blocked at the reachability step even though the route exists. If route patterns are missing, there’s no defined path to handle the dialed number, so the system can’t route the call even with a valid CSS. If the trunk or gateway is down, there’s no signaling or media path to reach the next hop, so the call cannot proceed regardless of the dial plan. Because any of these issues can independently cause a call routing failure, the scenario that encompasses all of them is the most accurate choice.