OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? (Choose Three.)
A.
Each OSPF area requires a loopback interface to be configured.
B.
Areas may be assigned any number from 0 to 65535.
C.
Area 0 is called the backbone area.
D.
Hierarchical OSPF networks do not require multiple areas.
E.
Multiple OSPF areas must connect to area 0.
F.
Single area OSPF networks must be configured in area 1.
Answer: B C E
Explanation:
I used to think the answers should be C D E and here is my explanation:
OSPF can use an active interface for its router ID, so a loopback interface is not a must -> A is incorrect.
OSPF Area is a 32-bit number so we can use up to 232 – 1 = 4294967296 – 1 (since Area 0 is the first area). Remember that only process ID is a 16-bit number and ranges from 1 to 65535 -> B is incorrect.
F is incorrect too because single area OSPF netwoks must be configured in Area 0, which is called the backbone area.
For answer D, it is a bit hard to guess what they want to say about “hierarchical” but we should understand “Hierarchical OSPF networks” as “OSPF networks”. D is correct bercause we can only have one area (area 0 – the backbone area) for our networks.
Yes, this one is also WRONG … Right answers are
B – C – E
B is correct—process-ID is a number between 1-65,535. area-id can use any number but is good practice to use 0 with single-area OSPF. Makes it easier if network is later configured as multiple OSPF areas where area 0 becomes the backbone area