This CAS-004 practice question tests your understanding of security architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
During a merger, two companies need to integrate their networks securely. Company A uses RFC 1918 addresses (10.0.0.0/8) and Company B also uses 10.0.0.0/8. Which architectural solution prevents routing conflicts and maintains security?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy network address translation (NAT) on the border routers to translate one company's addresses to a unique range
NAT at the boundary translates overlapping addresses, allowing communication without conflict. Option A is wrong because it disrupts routing. Option B is wrong without NAT, traffic may not route correctly. Option D is wrong as it does not address IP overlap.
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.
✗
Configure a site-to-site VPN with no address translation
Why it's wrong here
VPN without NAT will have routing conflicts due to overlapping IPs.
✗
Enable direct BGP peering between the two networks
Why it's wrong here
Direct peering with overlapping subnets will cause routing issues.
✗
Implement a firewall between the networks and allow all traffic
Why it's wrong here
Firewall alone does not solve IP overlap; traffic may not reach the correct host.
✓
Deploy network address translation (NAT) on the border routers to translate one company's addresses to a unique range
Why this is correct
NAT resolves IP overlap and allows secure communication.
Related concept
Static NAT maps one inside address to one outside address.
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.
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 CAS-004 NAT questions on configuration and troubleshooting.
Security Architecture — This question tests Security Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Deploy network address translation (NAT) on the border routers to translate one company's addresses to a unique range — NAT at the boundary translates overlapping addresses, allowing communication without conflict. Option A is wrong because it disrupts routing. Option B is wrong without NAT, traffic may not route correctly. Option D is wrong as it does not address IP overlap.
What should I do if I get this CAS-004 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 CAS-004 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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