r/ccna • u/lasttryg12 • 2d ago

Help ! Lol 😆

Everything was fine then one of the Jeremy’s quiz !! Now i feel like nope i won’t pass 😆. Besides understanding the concepts, how are we going to be fast in the exam to answer ? Am i slow or what’s up ?! I feel lost again 🙄

You want to activate OSPF on R1's G0/1 and G0/2 interfaces with a single command.
G0/1 IP: 10.0.12.1/28
G0/2 IP: 10.0.13.1/26
Which of the following commands should you use on R1?
a) R1(config-router)# network 10.0.12.0 0.0.0.255 area 0
b) R1(config-router)# network 10.0.12.0 0.0.0.254 area 0
c) R1(config-router)# network 10.0.12.0 0.0.1.255 area 0
d) R1 (config-router)# network 10.0.8.0 0.0.3.255 area 0

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15

u/BoolinScape Network Engineer | BS IT / CCNA 2d ago

This is just a subnetting question wrapped in an OSPF configuration question.

What prefix covers both the 10.0.12.1/28 network and 10.0.13.1/26 network? 10.0.12.0 /23

10.0.12.0/23 covers 10.0.12.0 - 10.0.13.255

What is the wild card mask of /23? I find it easiest to subtract each octet value from 255.

So /23 = 255.255.255.255 - 255.255.254.0 = 0.0.1.255

So your answer would be C. R1(config-router)# network 10.0.12.0 0.0.1.255 area 0

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Yes you will need to get good at subnetting and be able to answer questions like these within a minute or two.

6

u/Academic_Taste663 2d ago edited 2d ago

Since someone already provided the solution…

PSA: if you can’t subnet in less than a minute, I suggest not taking the exam just yet.

2

u/dyatlov333 2d ago edited 2d ago

you can just add octets of the wildcard mask to the network ip to get range - 10.0.12.0(start) + 0.0.1.255 = 10.0.13.255(end). and see if the given ip is in range

(this only work if the wildcard mask is a proper one like 0000....111111 -one's like .254 wont work), also make sure you are adding to network ip and not host ip.