Designing Cisco Enterprise Networks (ENSLD) — Question 134

An engineer must peer with an ISP for internet connectivity using BGP, initially, the engineer wants to receive only specific prefixes from the ISP and a default route. However, the solution must provide the flexibility to add prefixes in the future at short notice. The ISP has a two-week change process in place. Which route filtering solution must the engineer employ?

Answer options

• A. Request a limited internet routing table and a default route from the ISP and configure the BGP max-limit to 1 with an access list that permits only the specific internet prefixes and blocked networks
• B. Request only the required prefixes and default route be advertised from the ISO with whitelisted networks
• C. Request a full internet routing table and a default route from the ISP and configure inbound route filtering with a prefix list that permits the default route and required prefixes
• D. Configure outbound route filtering on the enterprise and ISP so that the enterprise tell the ISP which prefixes are required

Correct answer: C

Explanation

The correct answer is C because it allows the engineer to receive a full routing table while still ensuring that only the necessary prefixes and the default route are accepted through inbound filtering. Options A and B do not provide the flexibility needed for future changes, while D focuses on outbound filtering, which does not meet the requirements for receiving specific prefixes from the ISP.