Introduce and into BGP through the network command. Which is wrong? (Multiple choice)

Question

Options

• AJust match the prefix, and the mask length does not have to be strictly matched
• BThe mask length must be strictly matched
• CThe route cannot be an IP route, it can only be a direct route
• DThe route must exist in the IP routing table and be the best route

• A
  76% (52)
• B
  3% (2)
• C
  7% (5)
• D
  13% (9)

Explanation

Option A is the wrong statement because the BGP network command performs exact prefix and mask matching against the IP routing table - if you specify network 172.16.1.0 mask 255.255.255.0, BGP will only advertise that route if 172.16.1.0/24 exists exactly as written; a supernet like 172.16.0.0/16 will not trigger it.

B is a correct (true) statement - strict mask matching is precisely how the network command works, making B a valid description, not a wrong one. C is also correct - the route does not have to be a directly connected route; static routes and IGP-learned routes present in the routing table are valid candidates for advertisement via the network command. D is correct - the prefix must exist in the IP routing table and be the best (lowest-cost) route; a route that exists but is not selected as best will not be advertised.

Memory tip: Think of the BGP network command as a "photocopy machine" - it only copies what's in the routing table as an exact match (prefix + mask), not a rough approximation. If the mask doesn't fit perfectly, nothing gets advertised.

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