assigning Highest IP on each subnet is the default gateway to cooresponding VLAN

Question

Network Diagram:

I got 3 vlans

1st Management

Required hosts: 15

Network ID: 192.168.100.0/27
Range : 192.168.100.0/27 - 192.168.100.31/27
Highest IP default-gateway: 192.168.100.30/27

2nd USER

Required hosts: 70

Network ID: 192.168.100.32/25
Range : 192.168.100.32/25 - 192.168.100.159/25
Highest IP default-gateway: 192.168.100.158/25

3rd Guest

Required hosts: 10

Network ID: 192.168.100.160/28
Range : 192.168.100.160/28 - 192.168.100.176/28
Highest IP default-gateway: 192.168.100.174/28

So in Level 1 switch I put IP default-gateway: 192.168.100.30

So in Level 2 switch I put IP default-gateway: 192.168.100.30

On router:

f0/1.99 IP : 192.168.100.30/27

f0/1.10 IP : 192.168.100.158/25

f0/1.20 IP : 192.168.100.174/28

It doesnt work.

error: 192.168.100.160 overlaps with FastEthernet0/1.10

So what I am doing wrong ?

Answer 1

You have overlapping subnets. You can't assign the subnet ID at random, it's a function of the mask. Valid subnet ID's for 192.168.100.X/25 are either 192.168.100.0 or 192.168.100.128

The IP Address 192.168.100.158/25 is part of the 192.168.100.128/25 subnet with valid IP addresses from 192.168.100.129-254

To avoid overlap, use these subnets:

192.168.100.0/25
192.168.100.128/27
192.168.100.160/28