Routing Protocols Flashcards

What OSPF router type connects one or more areas to the OSPF backbone (Area 0)?

Answer: Area Border Router (ABR)

An ABR (Area Border Router) connects one or more OSPF areas to backbone Area 0 and maintains separate LSDBs for each area it belongs to.

What is the administrative distance of OSPF internal routes on a Cisco router?

Answer: 110

OSPF internal routes have an administrative distance of 110 in Cisco IOS, making them less preferred than EIGRP (90) but more preferred than RIP (120).

Which LSA type is generated by an ASBR to advertise external routes into the OSPF domain?

Answer: Type 5 (AS External LSA)

Type 5 AS External LSAs are originated by ASBRs and flooded throughout the entire OSPF domain except into stub areas.

In EIGRP, which concept refers to the best backup route that is guaranteed loop-free without requiring a query?

Answer: Feasible Successor

A Feasible Successor satisfies the Feasibility Condition (its Reported Distance < current Feasible Distance), guaranteeing it is loop-free and can be used immediately upon failure of the primary path.

What is the default OSPF hello interval on a broadcast (Ethernet) network type?

Answer: 10 seconds

On broadcast network types, OSPF uses a default hello interval of 10 seconds and a dead interval of 40 seconds (4x hello).

Which EIGRP metric components are used by default in the composite metric calculation?

Answer: Bandwidth and Delay

By default, EIGRP uses only Bandwidth and Delay (K1=1, K3=1) in its composite metric; Reliability, Load, and MTU have K-values of 0.

Which BGP technique artificially lengthens the AS path to make a route less preferred by external peers, influencing inbound traffic?

Answer: AS Path Prepending

AS Path Prepending repeats your own AS number multiple times in the AS_PATH attribute, causing external peers (who prefer shorter paths) to choose an alternate entry point.