A user has setup a VPC with CIDR 20.0.0.0/16. The VPC has a private subnet (20.0.1.0/24) and a public subnet
(20.0.0.0/24). The user’s data centre has CIDR of 20.0.54.0/24 and 20.1.0.0/24. If the private subnet wants to
communicate with the data centre, what will happen?
A.
It will allow traffic communication on both the CIDRs of the data centre
B.
It will not allow traffic with data centre on CIDR 20.1.0.0/24 but allows traffic communication on 20.0.54.0/24
C.
It will not allow traffic communication on any of the data centre CIDRs
D.
It will allow traffic with data centre on CIDR 20.1.0.0/24 but does not allow on 20.0.54.0/24
Explanation:
VPC allows the user to set up a connection between his VPC and corporate or home network data centre. If the user has
an IP address prefix in the VPC that overlaps with one of the networks’ prefixes, any traffic to the network’s prefix is
dropped. In this case CIDR 20.0.54.0/24 falls in the VPC’s CIDR range of 20.0.0.0/16. Thus, it will not allow traffic on that
IP. In the case of 20.1.0.0/24, it does not fall in the VPC’s CIDR range. Thus, traffic will be allowed on it.
D
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B
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0
why?
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D
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Hi
Can someone explain how this overlapping of CIDR works (at least in this case). I am trying to understand this networking concept better & I do understand it could be an overwhelming topic but trying to understand this better at least at a high level.
my understanding is –
20.0.0.0/16 could span a range – 20.0.0.1 – 20.0.255.244
how will 20.0.54.0/24 overlap with this?
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@Shiva Ramani
you already get it.
20.0.54.0/24 has a range of 20.0.54.0 – 20.0.54.255, so obviously it is part of the 20.0.0.1 – 20.0.255.244 range you mentioned.
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