350-501 MPLS and Segment Routing Practice Question
This 350-501 practice question tests your understanding of mpls and segment routing. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit. The output is from a Cisco router after configuring Segment Routing with TI-LFA.
R1# show isis fast-reroute summary
Number of prefixes with backup paths: 1
TI-LFA:
Primary Protection: Enabled
Node Protection: Enabled
SRLG Protection: Disabled
What does the output indicate about the TI-LFA protection on R1?
Refer to the exhibit. The output is from a Cisco router after configuring Segment Routing with TI-LFA.
R1# show isis fast-reroute summary
Number of prefixes with backup paths: 1
TI-LFA:
Primary Protection: Enabled
Node Protection: Enabled
SRLG Protection: Disabled
A
All prefixes have backup paths.
Why wrong: Only 1 prefix is shown to have a backup; this does not indicate all.
B
Only 1 prefix has a backup path.
The line 'Number of prefixes with backup paths: 1' confirms this.
C
0 prefixes have backup paths.
Why wrong: The output explicitly states 1 prefix has a backup path.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Only 1 prefix has a backup path.
The output shows that only one prefix has a backup path. Node protection is enabled, and SRLG protection is disabled.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
All prefixes have backup paths.
Why it's wrong here
Only 1 prefix is shown to have a backup; this does not indicate all.
✓
Only 1 prefix has a backup path.
Why this is correct
The line 'Number of prefixes with backup paths: 1' confirms this.
Related concept
Static NAT maps one inside address to one outside address.
✗
0 prefixes have backup paths.
Why it's wrong here
The output explicitly states 1 prefix has a backup path.
✗
2 prefixes have backup paths.
Why it's wrong here
The output states 1, not 2.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
Only 1 prefix is shown to have a backup; this does not indicate all.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
MPLS and Segment Routing — This question tests MPLS and Segment Routing — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Only 1 prefix has a backup path. — The output shows that only one prefix has a backup path. Node protection is enabled, and SRLG protection is disabled.
What should I do if I get this 350-501 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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