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VLSM odd problem

Today I was setting up a small network for a new client with the following equipment, 881 router,  2960 switch and a 1041 accesspoint.  The customer wanted 2 things,  a private LAN for their employees and a guest LAN via WIFI that was able to access the internet and nothing else.   I set this up and everything is working but here is my odd question and I am hoping someone can explain it to me so that I can understand why it would not work my original way.

Original network design.

Interface vlan1

     description Admin network for cisco equipment

     ip address 192.168.1.1 255.255.255.248

interface vlan2

     description Private network for employees

     ip address 192.168.1.9 255.255.255.224

interface vlan3

     description Guest network

     ip address 192.168.1.41 255.255.255.240

So that was my original plan,  but when I would try to apply the IP for interface vlan2, it would throw and error saying the ip overlapped with vlan1.  I do not understand this because  vlan1's network was 192.168.1.0 /29  so 192.168.1.0 - 192.168.1.7.  I am not sure why 192.168.1.8 /27 would overlap 192.168.1.8 - 192.168.1.39?

After being frustrated I ended up changing things around as follows and it worked fine,  which I do not understand why.

Interface vlan1

     description Admin network for cisco equipment

     ip address 192.168.1.49 255.255.255.248

interface vlan2

     description Private network for employees

     ip address 192.168.1.1 255.255.255.224

interface vlan3

     description Guest network

     ip address 192.168.1.33 255.255.255.240

It is the same network design I just did the largest networks first and the smallest last.  So if anyone can explain this to me I would really appreciate it cause I am not getting why it didnt work.

Thanks everyone!

LR

Everyone's tags (1)
1 REPLY
Purple

Re: VLSM odd problem

Because the range 192.168.1.9 255.255.255.224  runs from 192.168.1.1 -192.168.1. 30   so it does overlap with your first defined subnet . 

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