JN0-664 Exam Dumps : Service Provider Professional (JNCIP-SP)

The attached bit is a flag in an IS-IS LSP that indicates whether a router is connected to another area or level (L2) of the network. By default, L2 routers set this bit when they advertise their LSPs to L1 routers, and L1 routers use this bit to select a default route to reach other areas or levels through L2 routers. However, this may result in suboptimal routing if there are multiple L2 routers with different paths to other areas or levels. To ensure that L1 routers have only the most specific routes available from L2 routers, you can configure the ignore-attached-bit parameter on all L1 routers. This makes L1 routers ignore the attached bit and install all interarea routes learned from L2 routers in their routing tables.

Option A (Correct):

In IS-IS, the Designated Intermediate System (DIS) is elected based on the highest configured priority (as defined in Junos OS).

If priorities are equal, the router with the highest MAC address becomes the DIS.

A priority value of 10 will always override a lower priority (e.g., 1).

Prefer the route with the lower origin code. Routes learned from an IGP have a lower origin code than those learned from an exterior gateway protocol (EGP), and both have lower origin codes than incomplete routes (routes whose origin is unknown).