Networking 2 PLC's with different IP's

ceilingwalker

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ceilingwalker
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Hello All, I have two CompactLogix that I would like to network together however, they have different IP subnets. Is there a way to connect them without using a router and without changing all the IP's from one to match the other? Hopefully this question makes sense. Thanks
 
We need more information.


What is the physical and logical configuration of the network path between them? Are they on the same Ethernet LAN (Ethernet broadcast domain, i.e. are they connected via switches, and see packets of each other's MAC address? Or perhaps even connected directly to each other?

What is the configuration of the current IP addresses, subnet masks, and gateway IP addresses for each? Can you change any of those values?

Do they have serial ports?
 
I'm assuming since you used the term subnet its just the last actual host ID your referring to.

Example PLC A is on 192.168.1.100 and PLC B is on 192.168.2.100.

If that is true, then as others have already said, adjust your subnet mask to allow traffic to flow. Instead of 255.255.255.0 make them 255.255.0.0
 
ArcReactorKC said:
I'm assuming since you used the term subnet its just the last actual host ID your referring to.

Example PLC A is on 192.168.1.100 and PLC B is on 192.168.2.100.

If that is true, then as others have already said, adjust your subnet mask to allow traffic to flow. Instead of 255.255.255.0 make them 255.255.0.0
Click to expand...

If they are wildly different, you could use a NATR as a router...
 
I know you say you don't want to use a router - but....it does sound like a job for the NATR if the IP are massively different.

Just saying.
 
ArcReactorKC said:
I'm assuming since you used the term subnet its just the last actual host ID your referring to.

Example PLC A is on 192.168.1.100 and PLC B is on 192.168.2.100.

If that is true, then as others have already said, adjust your subnet mask to allow traffic to flow. Instead of 255.255.255.0 make them 255.255.0.0
Click to expand...
Best practice in this example would be to set the mask to 255.255.254.0, but that is specific to a /23 network size.
 
For this example (...1.100 and ...2.100), wouldn't that need 255.255.252.0 to supernet the 0, 1, 2, and 3 networks? Asking because I am facing a very similar situation as the OP.
 
Sorry for the delayed response. A different "fire" required my attention. In my example, one PLC is 10.0.41.x and the other is 192.168.1.x. They both have other h-ware in their LAN's, which is why it isn't a simple matter of changing just one PLC's IP. As I type this, I have a feeling that a router is going to be the only way to make this happen.
 
ceilingwalker said:
Sorry for the delayed response. A different "fire" required my attention. In my example, one PLC is 10.0.41.x and the other is 192.168.1.x. They both have other h-ware in their LAN's, which is why it isn't a simple matter of changing just one PLC's IP. As I type this, I have a feeling that a router is going to be the only way to make this happen.
Click to expand...


yes, that sounds like the solution, especially if they are on separate LANs.



you could also put a second ethernet card (module) into one compactlogix and connect it to the other LAN, but a gateway between the networks is probably a quicker solution.
 
ceilingwalker said:
Hello All, I have two CompactLogix
Click to expand...

What CompactLogix? some have dual ports and it may be easier

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1769-um021_-en-p.pdf

Connecting to Different EtherNet/IP Network Topologies
The CompactLogix 5370 L3 controllers have embedded switch technology
and two EtherNet/IP ports that let you use it in different EtherNet/IP
network topologies:
• Device Level Ring network topology - Both ports on the controller are
connected to the network with requirements about how the
connections are made.
• Linear network topology - Both ports on the controller are connected to
the network with requirements about how the connections are made.
• Star network topology - One port on the controller is connected to
the network.
For more information, see EtherNet/IP Network Topologies on page 125.
Click to expand...
 
ceilingwalker said:
Sorry for the delayed response. A different "fire" required my attention. In my example, one PLC is 10.0.41.x and the other is 192.168.1.x. They both have other h-ware in their LAN's, which is why it isn't a simple matter of changing just one PLC's IP. As I type this, I have a feeling that a router is going to be the only way to make this happen.
Click to expand...

Unless one of them is a 5380 with separately IP-addressable Ethernet ports, you will need a router, or a simpler NAT device such as the 1783-NATR or 9300-ENA, to perform the routing. The NAT will need to be at a location with physical access to both networks. For example, if located in the 192.168 panel, there will need to be a 10.0.41 drop into that same panel to plug into the public side of the NAT.
 

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