A large enterprise network running IS-IS wants to deploy IGP traffic engineering, but they are concerned that the IS-IS default metrics are not flexible enough. Which feature must be enabled to…

IS-IS Narrow Metrics use 6-bit values (0-63) and legacy TLVs that cannot carry the TE sub-TLVs required for traffic engineering, making them incompatible with TE extensions.

IS-IS DIS is the broadcast segment pseudo-node election mechanism and has no bearing on metric flexibility or traffic engineering attribute advertisement.

IS-IS Wide Metrics extend the metric field from 6 bits (narrow, max 63) to 24 bits (max 16,777,215) using extended TLVs such as TLV 22 (Extended IS Reachability) and TLV 135 (Extended IP Reachability). MPLS Traffic Engineering relies on these extended TLVs to advertise TE attributes including bandwidth, affinity, and SRLG values inside IS-IS LSPs. Enabling wide metrics is therefore the minimum required change to add TE support without altering the topology or deploying an additional protocol.

IS-IS Multitopology allows the protocol to maintain separate topologies for different address families such as IPv4 and IPv6, but it does not solve the metric range limitation or provide the extended TLVs needed for TE.