Identical systems IP

[bill4807]

Hi all,

I have a Question about differentiating IP addresses.
If i had two identical systems with about 7 IP address devices, would it be smart to make them different from system to system. In a case where these may land right next to each other in the plant.

Example system 1:
192.168.1.10, 20, 30, 40, 50, 60, 70

Example system 2:
192.168.1.11, 21, 31, 41, 51, 61, 71.

OR

Keep both systems the same.
I think making them different will allow me to know which one im actually in remotely if i have to be, or if the customer wants to pull data or hook up to network he will have some indication of which is which.

What do you think is best?

 

[Engineerj22]

Different IPs would be what I do.

 

[widelto]

++ Different

 

[PLCDontUQuitOnMe]

If you have a lot of identical machines I would keep the IP addresses the same from machine to machine for consistency, then use a NAT device in each panel. Only map the devices from each machine that you would actually need to connect to remotely, and give them unique IP addresses in the NAT table of the NAT device. Your IT guy will thank you.

 

[Operaghost]

Your examples certainly work. My concern would be having all those devices on a single subnet (192.168.1.x) can create a lot of broadcast or multicast traffic. That can affect performance.

I would generally suggest different IP ranges. For example, I would change the third octet and hopefully use a number that is meaningful. This would separate the different systems broadcast and multicast traffic and provide better performance.

System #1: 192.168.1.1
System #2: 192.168.2.1

etc...

The tricky part is when you want to connect to them you will need to make sure your device can access those IP addresses. If each system had their own switch and that device could assign your computer an IP address that could cut down on confusion.

But what PLCDontUQuitOnMe said has a lot of merit too. If you have multiple identical systems, keeping the IP addresses the same can make it easier for those less experienced. So no matter what system you are working on, the controller and other devices are always using the same IP address.

OG

 

[kckku]

If you have a lot of identical machines I would keep the IP addresses the same from machine to machine for consistency, then use a NAT device in each panel. Only map the devices from each machine that you would actually need to connect to remotely, and give them unique IP addresses in the NAT table of the NAT device. Your IT guy will thank you.

I would do this as well. We have a lot of identical machines and the PLC is always node number 1, HMI's are always 50, barcode readers are always 130, etc.

 

[Jim3846]

Your examples certainly work. My concern would be having all those devices on a single subnet (192.168.1.x) can create a lot of broadcast or multicast traffic. That can affect performance.


System #1: 192.168.1.1
System #2: 192.168.2.1

OG

If you dont want to go the route of a NAT, this suggestions makes more sense. Just remember to widen your laptop mask 255.255.0.0 to see this way of setting up the machines.

Some IT people dont like this widen out the mask but if you dont have the costs covered in a NAT, this would be the route i would go.

 

[James Mcquade]

I would use different IP addresses.
if you ever connected them to a plant network, nothing would work, they have the same ip address and create a conflict on the network. i had that happen to me, someone in maintenance powered up an old display board that had the same ip address as a barcode scanner. i had to create a new ip network for all our scanners.
james

 

[andrewwei]

You cannot have 2 identical ip address on the same subnet. If you only have one subnet, such as 192.168.1.0/24, you can divide this subnet into 2 subnets. You should NOT assign system 1 as Odd number, system 2 as even number. You need a managed switch or layer 3 switch to divide subnets. If want the 2 systems talk to each other, you don't need to divide subnets.
for example system 1 should be 192.168.1.1 -- 126, then system 2 should be 192.168.1.129 -- 254.

 

[andrewwei]

If you dont want to go the route of a NAT, this suggestions makes more sense. Just remember to widen your laptop mask 255.255.0.0 to see this way of setting up the machines.

Some IT people dont like this widen out the mask but if you dont have the costs covered in a NAT, this would be the route i would go.

255.255.0.0 wouldn't be bad for traffic?

 

[Operaghost]

You cannot have 2 identical ip address on the same subnet. If you only have one subnet, such as 192.168.1.0/24, you can divide this subnet into 2 subnets. You should NOT assign system 1 as Odd number, system 2 as even number. You need a managed switch or layer 3 switch to divide subnets. If want the 2 systems talk to each other, you don't need to divide subnets.
for example system 1 should be 192.168.1.1 -- 126, then system 2 should be 192.168.1.129 -- 254.

Everyone has their own opinion. You might say do not do it the way I suggested, and I might say the same about your method. Doesn't make either of them wrong.

Even if the systems needed to talk with each other, I would go with either the suggestion to use NAT, or my method and use VLANs. I would not recommend widening the subnet mask. As you asked, it will make for a single large broadcast domain which is definitely bad for traffic. The switch would need to support inter VLAN routing. I would make the VLAN number the same number I use for the third octet. That is the method I used when I taught Cisco courses. Although I usually incremented them by 10. So VLAN 10 would use 192.168.10.xx and VLAN 20 would use 192.168.20.x.

If the systems do not need to talk with each other, I would still consider changing IP addresses. Some day, someone will connect those systems together and all heck will ensue.

OG

 

[NetNathan]

Absolutely you want different IP addresses for each piece of equipment.
You do not have to skip around, you can do them sequentially, like 192.168.11, 12, 13, 14, 15, 16, and 17.

ON the systems we build, I use a low number for the plc on the equipment and add 100 for the HMI.
My customers use numbers for the equipment designation, which makes deciding on IP address simple. So furnace 10 plc gets 192.168.1.10 and the HMI is 192.168.1.100. Makes it easy to know who is who.

 

[bill4807]

All great responses to think about thank you.
The systems will not talk to each other directly.
Each system has its own set of ethernet switches.


I do not have a NAT currently for each system nor are we responsible for networking to the plant.
But i would like to make it as seemless as possible for them when they decide to hook to the plant.

 

[mad4x4]

Keep each machine the same, and then put in a Connection Gateway device (M2M) such as a ****
This will also act as a firewall between the machine and the Customer (or machine and machine) to protect your machine from "****" from their network.

Only reason to use various ips if you are say "Stacking" 3 Machines together on same network and then putting in a common HMI that controls all three machines or machine 1 needs data from machine 2 etc.

https://www.mac-solutions.net/****-cosy

https://www.phoenixcontact.com/en-gb/products/security-router-for-the-din-rail-fl-mguard-1102-1153079

 

[bill4807]

I know im continuing to add detailed information i should have started with..
I can get remote access for programming through the HMI. It has it built in.
This is why I wasn't going to use an E*w*n this time around. By using the HMI independently in each system as access if IPs are the same i will not know which system im in, unless I throw a comment in one of the programs maybe, then i can check.

I also am using L3x controller, which has dual IP, which i planned on leaving A2 open so they could use it for their plant whenever they decide to.