350-501 · Question #152
A network team has failed to implement IS-IS multitopology. What is the reason for it?
The correct answer is B. The routing process did not support extended metrics. The failure to implement IS-IS multitopology in a network is likely due to the routing process not supporting extended metrics, which are often essential for maintaining separate and distinct path calculations for different topologies.
Question
A network team has failed to implement IS-IS multitopology. What is the reason for it?
Options
- AThe router did not support VRFs.
- BThe routing process did not support extended metrics.
- CThe router did not have Cisco Discovery Protocol and Cisco Express Forwarding disabled.
- DThe routing process supported Level 1 only.
How the community answered
(27 responses)- A4% (1)
- B74% (20)
- C15% (4)
- D7% (2)
Why each option
The failure to implement IS-IS multitopology in a network is likely due to the routing process not supporting extended metrics, which are often essential for maintaining separate and distinct path calculations for different topologies.
VRF support is unrelated to the fundamental ability of a single IS-IS process to run multiple topologies.
IS-IS multitopology (MT-IS-IS) often requires the use of extended metrics to provide sufficiently granular and independent metric calculations for different topologies (e.g., IPv4 and IPv6) within a single IS-IS instance. If the routing process only supports standard, limited 6-bit metrics, it becomes challenging or impossible to implement distinct path selection for multiple topologies effectively.
Cisco Discovery Protocol (CDP) and Cisco Express Forwarding (CEF) are operational features and their status does not prevent the implementation of IS-IS multitopology.
IS-IS multitopology can be implemented in both Level 1 and Level 2 routing, so supporting only Level 1 does not inherently prevent multitopology functionality.
Concept tested: IS-IS Multitopology Requirements
Source: https://www.cisco.com/c/en/us/td/docs/iosxr/cisco_iosxr_is_is_deployment_guide/cisco_iosxr_is_is_deployment_guide_chapter.html#id_85623
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