Multiple Machines with Same IP Address

[caseyshaffer]

I work in a factory that has 100's of machines that all run identical programs.  I would like to connect them to a network so I can access them remotely and also collect data.  Trouble is all of the machines have the same IP address because they are running the same program.  Is there a way to network them together using each unique MAC address instead of IP address for routing purposes? 

[John Blakley]

Not that I'm aware of. Are they not networked now at all? Your best bet would be to put them on a subnet away from everything else on a separate vlan so you'll know what addresses to collect from.

[caseyshaffer]

They are currently not networked together, but I would like them to be.  Each machine has several computers inside of it that runs different parts of the machine that are networked together.  I would like to connect each machine to some type of router (or unmanaged switch) without changing all of the IP addresses.

Each machine has 3 PC's with unique IP addresses connected to an unmanaged switch.  We have hundreds of these machines, but the 3 PC's within each different machine have the same IP address.  To change the IP addressess of all those PC's would be very cumbersome. 

[John Blakley]

You won't be able to get this to work unfortunately...IP conflicts abound. It sounds like you have a lot of work ahead of you.

Once you connect your system to a switch and then connect another system to the same switch, the workstations will start broadcasting to the switch. The switch is going to start collecting mac addresses to put in it's cam table and associate those macs to IPs in the arp table. You are going to run into some serious issues. Sorry to be the bearer of bad news, but you're going to need to change the IP addresses to be unique. I would highly suggest getting a DHCP server on that subnet though so you can somewhat keep them managed even if separate from the rest of the network.

[hobbe]

Hi

Yes it is possible to do that, but it will cost a lot more than it will be worth.

What you can do is to put a NAT-Device infront of the units.

This will shield them from eachother and you will be able to connect to each of the units via nat and pat from the NAT unit.

However if you have 100s of them then you need 100s of NAT units.

to try to make a network with the units and then assign "new" ip addresses via the mac addresses will just become a realy realy bad solution in the end.

sorry that i am not of more help

Good luck

HTH

[davy.timmermans]

Creating static ARP entries is a possibility but not scalable. This should be done at the devices where the subnet of the machines is advertized

ip arp arpa

ip arp arpa

but as I said - not really scalable

[fb_webuser]

Would there be a way of using private VLANs for the solution?

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Posted by WebUser Les Waller Mba Cissp

[fb_webuser]

There are a number of responses on our Facebook page as well. Check out http://www.facebook.com/CiscoSupportCommunity/posts/220126618085479

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Posted by WebUser Cisco NetPro

[Ronny Kern]

try VRF

same Problem in this post

https://community.cisco.com/t5/network-management/multiple-global-to-vrf-nat/td-p/4776679