This 350-601 practice question tests your understanding of 350-601 exam topics. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An engineer is designing a spine-leaf fabric using eBGP for the underlay. The spine switches are in AS 65000 and each leaf switch uses a different private AS from 65001 to 65010. For optimal convergence and to avoid BGP path hunting, which BGP feature should be configured on the spines?
allowas-in 1
Allowas-in 1 permits the spine to accept updates containing its own AS once, which is needed when leaf uses spine AS as part of AS path.
disable-peer-as-check
Why wrong: This disables AS path validation but is insufficient for loop prevention.
bestpath as-path multipath-relax
Why wrong: For load balancing, not for AS path issue.
maxas-limit 10
Why wrong: Limits AS path length but does not solve receipt of own AS.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
allowas-in 1
In a BGP underlay with a common spine AS and unique leaf AS, 'allowas-in' or 'disable peer-as-check' can cause loops. Typically, spines set 'maxas-limit' but the correct technique is to use 'allowas-in' on the spines to accept the spine's own AS in updates (since leaf might send routes with spine AS). However, the recommended approach is to use 'remove-private-as' on the spines or set 'allowas-in 1' to accept one occurrence of the spine AS.
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
For each option: why learners choose it and why it is or isn't the right answer here.
allowas-in 1
Why this is correct
Allowas-in 1 permits the spine to accept updates containing its own AS once, which is needed when leaf uses spine AS as part of AS path.
Related concept
Static NAT maps one inside address to one outside address.
disable-peer-as-check
Why it's wrong here
This disables AS path validation but is insufficient for loop prevention.
bestpath as-path multipath-relax
Why it's wrong here
For load balancing, not for AS path issue.
maxas-limit 10
Why it's wrong here
Limits AS path length but does not solve receipt of own AS.
Common exam traps
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.
Detailed technical explanation
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.
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
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
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 350-601 NAT questions on configuration and troubleshooting.
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FAQ
Static NAT maps one inside address to one outside address.
The correct answer is: allowas-in 1 — In a BGP underlay with a common spine AS and unique leaf AS, 'allowas-in' or 'disable peer-as-check' can cause loops. Typically, spines set 'maxas-limit' but the correct technique is to use 'allowas-in' on the spines to accept the spine's own AS in updates (since leaf might send routes with spine AS). However, the recommended approach is to use 'remove-private-as' on the spines or set 'allowas-in 1' to accept one occurrence of the spine AS.
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 350-601 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jul 4, 2026
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