350-401 · Question #522
AN engineer is implementing a route map to support redistribution within BGP. The route map must configured to permit all unmatched routes. Which action must the engineer perform to complete this task
The correct answer is D. Include a permit statement as the last entry. Route maps implicitly deny routes that do not match any configured statements; to permit all unmatched routes, an explicit permit statement must be included as the very last entry.
Question
AN engineer is implementing a route map to support redistribution within BGP. The route map must configured to permit all unmatched routes. Which action must the engineer perform to complete this task?
Options
- AInclude a permit statement as the first entry
- BInclude at least one explicit deny statement
- CRemove the implicit deny entry
- DInclude a permit statement as the last entry
How the community answered
(33 responses)- A15% (5)
- B9% (3)
- C3% (1)
- D73% (24)
Why each option
Route maps implicitly deny routes that do not match any configured statements; to permit all unmatched routes, an explicit permit statement must be included as the very last entry.
Including a permit statement as the first entry would only permit routes that specifically match its criteria at the beginning of the evaluation, not those unmatched by subsequent entries.
Including an explicit deny statement would discard routes that match its conditions, which is contrary to the requirement of permitting all unmatched routes.
The implicit deny is a fundamental behavior of route maps and cannot be removed; it can only be overridden by an explicit statement as the final entry.
Route maps have an implicit 'deny all' statement at their end, meaning any route that does not match a `match` clause in a preceding `permit` or `deny` entry will be dropped. To permit all unmatched routes, an explicit `permit` statement without any `match` clauses must be added as the final entry (highest sequence number) in the route map, overriding this implicit deny.
Concept tested: Route map implicit deny override
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/command/bgp-cr-book/bgp-cr-r1.html#wp1091217094
Topics
Community Discussion
No community discussion yet for this question.