An engineer is creating a design to enable IPv6 to run on an existing IPv4 IS-IS network. The IPv4 and IPv6 topologies will match exactly, and the engineer plans to use the same router levels for…

Question

Options

• Asingle topology without enabling transition feature
• Bsingle topology with transition feature enabled
• Cmulti topology with transition feature enabled
• Dmulti topology without enabling transition feature

• A
  77% (36)
• B
  13% (6)
• C
  6% (3)
• D
  4% (2)

Explanation

IS-IS single topology mode requires that IPv4 and IPv6 share the exact same topology-same interfaces, same metrics, and same adjacencies-running a single SPF calculation for both protocols. Since the engineer's design explicitly states the IPv4 and IPv6 topologies will match exactly and the same router levels will be used per interface, single topology is the correct choice. The 'transition feature' (option B) is only needed when migrating an existing multi-topology deployment to single topology, allowing routers to temporarily advertise both MT and non-MT TLVs simultaneously during the migration window. Since this is a fresh design with matching topologies, no transition is needed. Multi-topology (options C and D) would be required only if the two protocol topologies differed-for example, if some links were IPv4-only or IPv6-only.

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