have 2 machines each controlled by contrologix with ethernet/ip also using Ntron enet switches 508tx
each machine is on seperate networks 191.1.17.??? on one and 192.168.124.??? on the other.

can these 2 networks be tied together using a switch ? and without having to change IP addresses of either machine?

for the purpose of being able to connect to either system from a single location

Thanks Guys

No Network guru, but with the correct gateway and subnet settings it might be doable. One little question 191 is a routable network if I remember correctly and 192 is a private network so this mat pose problems for you.

Yes, you can do it, but the answer is that it is very, very ugly. Set all the network masks to 0.0.0.0 (no mask). This effectively means that all possible IP addresses are local. You will NOT be able to communicate with the machines outside of the local LAN (not necessarily a bad thing) because any machine with a "wide open" mask can't talk to a gateway (router).

It doesn't have to be as destructive for the PC's. In Windows, you can set multiple IP addresses on a single NIC card. Set up the PC with a proper mask and gateway IP address for the primary IP address. Then set up a secondary IP address with a reasonable mask (such as 255.255.255.0). The PC will recognize both PLC's as being on the local LAN and will properly route everything else to the gateway.

The "correct" way to solve this problem is with "IP masquerading" or 1:1 NAT translation. To do this, you need a router or a firewall. The Hirschmann EAGLE mGuard (also sold under the name innomation) costs about $1300 and can easily do the translation to make one of your networks "appear" mapped onto the other network. You can also buy a cheaper Cisco 1811 to do the same thing but you have to use Cisco's CLI/IOS interface and you will lose having a DIN rail mount device with industrial power ratings and the ability to collect diagnostic information from the firewall through Ethernet/IP.

Nothing in N-Tron's line lets you do this. Their gear is relatively primitive and somewhat overpriced.

Yep ugly. Bad idea. To clarify:
1. I think a subnet mask of 252.0.0.0 would do it. You are combining an (RFC 1917) non-routable range with another range. Very screwy.
2. Binding multiple IP addresses could work. Try it out - I've seen this randomly "lock up" industrial hardware before.
3. NAT would work, but any cisco router could route between the 2 networks. Just like the "router on a stick" CCNA labs with subinterfaces (or separate interfaces). Seems really silly, though...

Why not just change your address ranges to something that makes sense?

well just the fact of having to change ip addresses on about 30 VFD's, 3 HMI's, controller, several point i/o racks.

I hear you. Unfortunately changing the subnet masks represents nearly the same amount of work (downtime) as changing the address range. You can do it with a router, but you'll need someone who knows what they're doing with networking. I'm not usually a fan of saying that you need an "expert", but this is one of those cases. The potential exists to create more downtime in a failed implementation than you would by correcting your address scheme.

The takeaway here is:
1. Determine your requirements
2. Come up with an addressing scheme that makes sense
3. Fix your issues during scheduled downtime

This is a really simple problem with a simple solution. The "Band Aide" fixes are complicated, expensive, and ultimately create problems.