Making several servers use the same IP address

I am trying to use ~40 server for mobile kits.  These kits include a piece of equipment that has to have a hard coded IP address for the server.  These kits go on mobile off line tasks and then return to upload/download data.  We would like to have the ability for all 40 machines to use the same IP address,, and have the network be able to connect several at a time for the upload/download process.  We have been using this system for years with the IP addresses being different.  

I have 20 VLANs that I can use for separating the various servers, but I can't get any of the three Cisco routers I have to test with to allow me to put on multiple sub interfaces.  My plan was to setup 10-20 sub interfaces and NAT to a 172.16.100.x address for each sub interface.  Would I need to use a firewall or a different router for this?
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I'm a little confused as to what you are trying to accomplish. You can not have several computers on the same lan with the same ip address. The computers will not know which is which. You can have a load balancer at one ip address that sequentially routes incoming requests to different ip addresses on the local lan. From the outside it would appear that a single ip address is handling all the traffic (e.g.
The only other way to do what you are asking (and this is probably a bad idea) is to buy 40 NAT routers and attach a computer to each one. The NAT routers will get their ip address via dhcp or something else and then each computer can have the same ip address. In essence, you will be creating 40 lans, each with their own 192.168.x.x class b space.
Dan CraciunIT ConsultantCommented:
Q: if you have the same IP on multiple destinations, how do you expect the router to know where you intend to send the packages?

Possible solutions:
1. use USB Ethernet cards. Then assign addresses to those using DHCP.
2. use multiple routers.
3. use DHCP on the servers.

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leecashionAuthor Commented:
Yes, I expect to need multiple subnets.  I have 20 VLANs reserved at the three locations involved. The "servers" are laptops used in mobile kits.  They are pulled off of buses and vans daily for update.  We can't really use DHCP for them as they are also the DHCP servers for their mobile kits.  USB interfaces would work for our main location, but we have non-technical staff at the other two.  

Here is a quick drawing of what I am trying to do.  I know it is an odd setup.
Dan CraciunIT ConsultantCommented:
You could assign an additional static IP for each server with each having a different IP, on a different subnet (for ex to
Then you would need a router that would ignore the conflicting IPs and use the second class.

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leecashionAuthor Commented:
That might be the only solution we have.  I might be able to set up private VLANs to get around the conflict issues.
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