Implementing Cisco Service Provider Advanced Routing Solutions (SPRI) — Question 118

What are two major differences between OSPF and IS-IS routing protocols? (Choose two.)

Answer options

• A. OSPF uses IP protocol 89 for encapsulation, and IS-IS uses an IEEE 802.3 standard-based protocol for encapsulation.
• B. OSPF partially refreshes the LSA database every 30 minutes, and IS-IS refreshes the complete database table every 60 minutes.
• C. An OSPF-enabled router is part of only one area, but an IS-IS-enabled router is part of multiple areas.
• D. The OSPF default administrative distance is 115, and the default administrative distance for IS-IS is 110.
• E. The OSPF DR role can be pre-empted only when the active DR goes down, but the IS-IS DR role can be taken by a router with higher priority at any time.

Correct answer: A, E

Explanation

The correct answer includes A and E because OSPF and IS-IS differ in their encapsulation protocols and the way the DR role is managed. Option B is incorrect as OSPF does not refresh LSAs based on a 30-minute timeline, and option C is misleading since OSPF can be in multiple areas with proper configuration. Option D is incorrect because the administrative distance values provided are accurate but do not highlight a major functional difference.