ACSP OSPF Routing Configuration 5 — Questions and Answers
Question 1: An Aruba switch has two equal-cost OSPF paths to a destination. What is the default OSPF behavior for traffic across these paths?
- Equal-cost multipath (ECMP) load balancing up to the configured maximum paths (Correct answer)
- Only the path through the lower router-id is used
- Traffic is load balanced only if the paths are in the same area
- The path with the lower next-hop IP is preferred
Correct answer: Equal-cost multipath (ECMP) load balancing up to the configured maximum paths
OSPF installs multiple equal-cost routes in the RIB enabling ECMP; AOS-CX supports configuring the maximum number of ECMP paths.
Question 2: What does configuring 'ip ospf cost 50' on an Aruba switch interface accomplish?
- It manually overrides the automatically calculated cost, influencing path selection (Correct answer)
- It sets the reference bandwidth to 50 Mbps for that interface
- It changes the hello interval to 50 seconds
- It limits OSPF to 50 neighbor adjacencies on that interface
Correct answer: It manually overrides the automatically calculated cost, influencing path selection
The 'ip ospf cost' command manually sets the interface cost, overriding the auto-calculated value, allowing administrators to influence which path OSPF prefers.
Question 3: In an Aruba OSPF network, which LSA type is flooded only within its originating area and describes the router's own links?
- Type 1 Router LSA (Correct answer)
- Type 2 Network LSA
- Type 3 Summary LSA
- Type 5 AS External LSA
Correct answer: Type 1 Router LSA
Type 1 Router LSAs are generated by every OSPF router and describe all its links and states; they are flooded only within the originating area.
Question 4: An Aruba switch running OSPF shows a neighbor stuck in INIT state. What is the most likely cause?
- The remote router receives hellos but the local router's hello is not being received by the remote router (Correct answer)
- Hello intervals do not match between the two routers
- The area IDs are mismatched between the two routers
- The remote router has OSPF authentication enabled
Correct answer: The remote router receives hellos but the local router's hello is not being received by the remote router
INIT state means the local router sees the remote router's hellos but is not yet listed in the remote router's hello packet, indicating a one-way communication problem.
Question 5: What is the administrative distance of OSPF routes on an Aruba AOS-CX switch by default?
- 90
- 110 (Correct answer)
- 115
- 120
Correct answer: 110
OSPF has a default administrative distance of 110 on Aruba AOS-CX, the same as Cisco IOS, used to prefer routes from different routing protocols.
Question 6: When OSPF is configured on an Aruba switch with multiple areas, what is the requirement for inter-area communication?
- All non-backbone areas must connect directly or via virtual link to Area 0 (Correct answer)
- All areas must have at least one ABR connecting them to another area
- Non-backbone areas can communicate directly without passing through Area 0
- Each area must have a unique DR to facilitate inter-area routing
Correct answer: All non-backbone areas must connect directly or via virtual link to Area 0
OSPF's hierarchical design mandates that all non-backbone areas connect to Area 0 (backbone), either directly or through a virtual link, for inter-area route exchange.
Question 7: On an Aruba switch, what is the function of the OSPF 'area range' command configured on an ABR?
- It summarizes multiple intra-area routes into a single Type 3 LSA advertised to other areas (Correct answer)
- It limits the number of Type 1 LSAs generated within the area
- It defines which networks are eligible for redistribution into OSPF
- It sets the cost for all routes within the specified address range
Correct answer: It summarizes multiple intra-area routes into a single Type 3 LSA advertised to other areas
The 'area range' command on an ABR aggregates specific intra-area prefixes into a single summary Type 3 LSA sent to other areas, reducing routing table size.
ACSP OSPF Routing Configuration 5
An Aruba switch has two equal-cost OSPF paths to a destination.
What is the default OSPF behavior for traffic across these paths?