350-501 Automation and Assurance Practice Question
Which TWO are possible causes for a NETCONF session failing to establish with a Cisco IOS-XE device?
⚠ Common exam trap
Cisco often tests the distinction between session establishment failures (caused by transport or authentication issues) and operational failures (caused by incorrect YANG models or data), leading candidates to confuse namespace errors with connectivity problems.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TCP port 830 is blocked by a firewall
NETCONF uses TCP port 830 as its default transport port (per RFC 6242). If a firewall blocks this port, the TCP three-way handshake cannot complete, preventing the NETCONF session from establishing. This is a common network-layer cause of session failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The device is running IOS-XR
Why it's wrong here
IOS-XR supports NETCONF, so this would not prevent session establishment.
- ✗
The YANG module namespace is incorrect
Why it's wrong here
YANG namespace is relevant for data operations, not for session establishment.
- ✗
NTP is not synchronized
Why it's wrong here
NTP synchronization is not required for NETCONF session establishment.
- ✓
TCP port 830 is blocked by a firewall
Why this is correct
NETCONF over SSH uses port 830 by default; if blocked, the TCP connection fails.
- ✓
NETCONF is not enabled or SSH is not configured for NETCONF
Why this is correct
If the device does not have NETCONF enabled or SSH is not configured for NETCONF, the session will not establish.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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