Which difference must an engineer consider when choosing whether to implement OSPF or IS-IS as the routing protocol on the network?

Question

Options

• AThe OSPF DR election process is deterministic, and the IS-IS DS election process is not
• BTo support fast convergence, OSPF uses the LSA arrival timer and IS-IS uses the PRC-interval
• CIS-IS supports ordinary, stub, totally-stub, and NSSA areas, but OSPF supports only stub areas.
• DIS-IS links are associated with either a Level 1 area or a Level 2 area at one time, but OSPF links

• B
  92% (24)
• C
  4% (1)
• D
  4% (1)

Explanation

A meaningful implementation difference between OSPF and IS-IS relates to their fast convergence tuning timers: OSPF uses an 'LSA arrival' timer (minimum interval between receiving the same LSA from any neighbor) to throttle SPF recalculation triggers, while IS-IS uses a 'PRC-interval' (Partial Route Calculation interval) to pace incremental SPF calculations for leaf-node changes. Understanding these distinct timer mechanisms is important when tuning sub-second convergence. Option A is false - IS-IS DIS election is also deterministic (highest priority, then highest MAC address). Option C is backwards - OSPF supports ordinary, stub, totally-stub, and NSSA area types; IS-IS only distinguishes between Level 1 and Level 2, with no equivalent NSSA concept. Option D is incomplete/misleading - IS-IS assigns level to the router interface adjacency, not the link itself in the same exclusive way described.

No community discussion yet for this question.