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MX84 Constant Subnet Overlap

SOLVED
Conversationalist

MX84 Constant Subnet Overlap

The message body contains just been thrown in at the deep end in looking after our small corporate network. We have carried out some updates to hardware and currently have a 100mb leased line coming in to a Cisco ISR4331 router which was all provided by our ISP.

 

 

I then have the Meraki MX84 sat between the ISR4331 and our new Cisco SGP300-28PP switches. One switch has all our data traffic with AD / File Server and desktops etc and the other has our new IP Phones connected.

 

When setting up I wanted to split the VoIP and Data on to 2 seperate VLANs so fault finding etc is made a little simpler. Our old IT contractor setup the old network using a 0/16 subnet and everything went through the one subnet with no VLAN which made everything messy when you looked at our old firewall dashboard and our servers were all set to Static IP's withing this subnet.

 

Now the problem arises!

 

I can setup VLAN1 for Data using the following info in the meraki dashboard:

 

VLAN Name: DATA

Subnet: 10.120.0.0/16

MX IP: 10.120.0.1

VLAN ID: 1

Group Policy: None as yet

 

This will save perfectly fine and work as required. However when I go to tad the VoIP VLAN using the following details I get an Subnet Overlap error when I save the config. However I can't see where the subnet overlap is

 

VLAN Name: VoIP

Subnet: 10.120.1.0/16

MX IP: 10.120.1.1

VLAN ID: 2

Group Policy: None as yet

 

Weirdly if I change the subnets to 0/24 it works fine. As I said I am new to this so I am sorry if my question / problem is stupidly simple. If I can use the 0/16 subnets it would save a lot of time having to reconfigure the servers and avoid any connectivity issues to staff working in the office and over VPN.

 

I would ask our previous contractor but due to the nature of why we have dropped them I can't really go back to them.

 

Any help is welcome

Tags (4)
1 ACCEPTED SOLUTION

Accepted Solutions
ww
Head in the Cloud

Re: MX84 Constant Subnet Overlap

/16 is all that fits in the x.x of 10.120.x.x. and give you 65,536 adresses (so 10.120.1.0/16 is the same subnet)

use 10.119.x.x/16 for voip

or 10.120.0.0/24 and 10.120.1.0/24  (/24 = 256 adresses for each subnet) or   10.120.0.0/23 and 10.120.2.0/23 (/23 = 512 adresses for each subnet)

 

https://en.wikipedia.org/wiki/Private_network

2 REPLIES 2
ww
Head in the Cloud

Re: MX84 Constant Subnet Overlap

/16 is all that fits in the x.x of 10.120.x.x. and give you 65,536 adresses (so 10.120.1.0/16 is the same subnet)

use 10.119.x.x/16 for voip

or 10.120.0.0/24 and 10.120.1.0/24  (/24 = 256 adresses for each subnet) or   10.120.0.0/23 and 10.120.2.0/23 (/23 = 512 adresses for each subnet)

 

https://en.wikipedia.org/wiki/Private_network

Highlighted
Conversationalist

Re: MX84 Constant Subnet Overlap

Great thanks for your help!!!

 

I thought it would be something simple that I'd overlooked!

 

Thanks again

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