300-415 Question #410: Real Exam Question with Answer & Explanation

This question tests BGP (Border Gateway Protocol) route summarization, specifically how to configure an aggregate route for the 10.0.0.0/16 network and advertise that summary exclusively to a specific BGP neighbor (Router B). The key skill is knowing the correct IOS commands and

Router Deployment

Question

Drag and Drop Question. Drag and drop the code snippets from the bottom onto the boxes in the configuration to create a summary of the 10.0.0.0/16 network specifically for its neighbor router B. Not all options are used.

Explanation

Approach. The correct approach uses the 'aggregate-address' command inside the BGP router process to collapse more-specific routes (e.g., 10.0.x.x subnets) into a single /16 advertisement: 'aggregate-address 10.0.0.0 255.255.0.0 summary-only'. The 'summary-only' keyword suppresses the more-specific component routes so only the aggregate is advertised. To target neighbor Router B specifically, you pair this with 'neighbor [Router-B-IP] remote-as [AS-number]' and optionally a prefix-list or route-map applied outbound to that neighbor to ensure only the summary reaches it. The subnet mask for /16 is 255.255.0.0, which must be stated explicitly in Cisco IOS (not CIDR notation) within the aggregate-address command.

Concept tested. BGP route summarization (aggregation) using the 'aggregate-address' command with the 'summary-only' keyword, combined with neighbor-specific outbound advertisement control - a core BGP optimization topic on CCNP/ENCOR and similar exams.

Reference. Cisco IOS BGP Configuration Guide - Route Aggregation; RFC 4271 (BGP-4); CompTIA/Cisco exam objective: Route Summarization and BGP Path Attributes

Topics

#Route Summarization#Routing Protocol Configuration#IP Addressing#Network Advertisement

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