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bakoo-7292 avatar image
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bakoo-7292 asked bakoo-7292 answered

Azure Subnet address range issue

Hello, This is bonah koo.
I think I got some bugs in Azure Vnet, especially on Subnet prefix.
ok. here is the thing.
I assigned vnet address range to 10.2.0.0/16 , and this means I can use 255*255 for sure(which is 10.2.0.0 ~ 10.2.255.255)
And I am trying to subnetting this thing to 3 subnet.
Let's say, snet-1, snet-2, snet-3.

Here is the problem start. let's give you some examples here.

1. Assigning same subnet bits.
I assigned subnet something like this.

snet-1 : 10.2.0.0/26,
snet-2 : 10.2.0.64/26
snet-3 : 10.2.0.128/26

and this test is working absolutely fine.
134561-example1.png
2. Assigning diffrenet subnet bits(descending)
I assigned subnet something like this.

snet-1 : 10.2.0.0/25
snet-2 : 10.2.0.128/26
snet-3 : 10.2.0.192/26

it works perfectly fine.
134515-example2.png
3. Assigning different subnet bits(ascending)

here is the problem starts.
I am trying to assign subnet something like this.
snet-1 : 10.2.0.0/27
snet-2 : 10.2.0.32/26
snet-3 : 10.2.0.96/26

and it doesn't work at all. and it says something like this.

10.2.0.32/26 is not a valid CIDR block. Use 10.2.0.0/26 instead.
This subnet address prefix overlaps with '10.2.0.0/27'.

what the hack? I think no issue is here, but somehow Azure calculator(decide the address range I think?)is something logical problem.
134505-example3.png

4. this one is also shocking test.
I assigned subnet something like this.

snet-1 : 10.2.0.0/27
snet-2 : 10.2.0.32/28
snet-3 : 10.2.0.128/25

and it works fine.
134506-example4.png
but if I assign
snet-1 : 10.2.0.0/27
snet-2 : 10.2.0.32/28
snet-3 : 10.2.0.48/27

It doesn't work.
134507-example5.png
somebody help me with this? or is it Azure bug issue?

Thanks












azure-virtual-network
example1.png (39.3 KiB)
example2.png (33.9 KiB)
example3.png (61.3 KiB)
example4.png (30.3 KiB)
example5.png (65.7 KiB)
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1 Answer

bakoo-7292 avatar image
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bakoo-7292 answered

This was my mistake...

The reason that it didn't work is
26bit can subnet only
10.2.0.0/26, 10.2.0.64/26, 10.2.0.128/26, 10.2.0.192/26 ...

So, the way I gave this something like 10.2.0.32/26 didn't make sense at all..

Maybe this could help someone later, I will leave this here.
Thanks

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