Refer to the exhibit. The company is running IS-IS in its core-A network engineer must segment the network into two areas to isolate departments. However, some networks must be shared from area 2 to…

While route maps and distribute lists can filter inbound routes, route-tagging provides a more robust and scalable solution for inter-area route control in IS-IS, especially for specific route sharing.

In IS-IS, route-tagging is a common and effective method to control route advertisement between Level 1 and Level 2 areas, especially when summarization or simple filtering isn't sufficient. By tagging routes at the L1/L2 boundary routers (like RB and RD) in one area, these tags can then be used in route-maps on the boundary routers of the other area to filter which routes are redistributed, ensuring only specific networks are shared.

Setting a unique area ID on each router is standard for IS-IS operation, but it only defines the areas and does not inherently implement selective route sharing or filtering between them.

Applying an ACL on an interface to deny unnecessary routes is a generic filtering method, but route-tagging, coupled with route maps, offers more granular control and is a best practice for inter-area route policy in IS-IS.