350-401 · Question #461
Refer to the exhibit. An engineer attempts to create a configuration to allow the Blue VRF to leak into the global routing table, but the configuration does not function as expected. Which action reso
The correct answer is A. Change the access-list destination mask to a wildcard.. To correctly match a network for route leaking from a VRF into the global routing table using an access-list, the access-list's destination mask must be specified as a wildcard mask.
Question
Refer to the exhibit. An engineer attempts to create a configuration to allow the Blue VRF to leak into the global routing table, but the configuration does not function as expected. Which action resolves this issue?
Exhibits
Options
- AChange the access-list destination mask to a wildcard.
- BChange the source network that Is specified in access-list 101.
- CChange the route-map configuration to VRF_BLUE.
- DChange the access-list number in the route map
How the community answered
(27 responses)- A59% (16)
- B11% (3)
- C7% (2)
- D22% (6)
Why each option
To correctly match a network for route leaking from a VRF into the global routing table using an access-list, the access-list's destination mask must be specified as a wildcard mask.
Standard access lists, when used with `match ip address` in a route-map for prefix matching, interpret the second operand as a wildcard mask. Changing the mask from `255.255.255.0` to `0.0.0.255` will allow `access-list 101` to correctly match routes for the `192.168.1.0/24` network, enabling the route leak.
The source network `192.168.1.0` is correct if that is the network intended to be leaked, but the issue lies with how the access-list mask is interpreted by the route-map for matching prefixes.
The route-map name `VRF_BLUE_TO_GLOBAL` is functional; changing it to `VRF_BLUE` does not address the access-list matching problem.
The access-list number `101` is referenced correctly within the route-map `match ip address 101` command; changing the number without a corresponding change in the access-list definition would break the configuration further.
Concept tested: Route-map access-list wildcard mask matching
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_pi/configuration/xe-3s/iri-xe-3s-book/iri-xe-3s-iproute-cfg.html
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