IP Addressing Office to Shop

gbradley · Jun 29, 2016

IP Address Pointers
If my IP address of my PC is: 10.0.1.1
Subnet mask: 255.255.252.0
Default Gateway 10.0.0.1
I want to be able to connect to a PLC with IP address: 10.0.2.1
What should my subnet be on my PLC? I have Subnet 255.255.240.0, and it isn’t working.
10.0.1.1 Office PC
10.0.1.2 Office PC
10.0.1.3 Office PC
10.0.1.4 Office PC

10.0.2.1 Shop Floor PLC
10.0.2.2 Shop Floor PLC
10.0.2.3 Shop Floor PLC
10.0.2.4 Shop Floor PLC
I'd ask the IT guy here, but he uses big words that are hard for me to understand.
You guys can explain it better for even a dolt like me.
Thanks

Archie · Jun 29, 2016

With a subnet of 255.255.252.0 means that your PC will try to access any of the following address ranges without trying to pass through a gateway:

10.0.0.xxx
10.0.1.xxx
10.0.2.xxx
10.0.3.xxx

So this brings the question.... Is there a gateway/router between your PC and the shop floor PLCs?

mk42 · Jun 29, 2016

1) If you're using a gateway/router, make sure you have that listed in your PLC as well as your PC.

2) In 90% of cases, you want the same subnet on your PC and the PLC. It may work otherwise, but it keeps things simple when the subnets are the same.

3) Based on the IP/Subnet you have listed, the PC should be able to talk directly to the PLCs without needing a router. Well, as long as they are actually on the same network.

4) If the PLC and PC are on different networks, then they need to have different IP ranges, and something needs to be reconfigured so they don't overlap.

gbradley · Jun 29, 2016

Archie said:
So this brings the question.... Is there a gateway/router between your PC and the shop floor PLCs?

Yes.
I have to figure out the IP of the gateway router don't I?

Archie · Jun 30, 2016

If there is a gateway/router, then you will need to know its address. It could be the 10.0.0.1 address. Try setting your subnet mask to 255.255.255.0

Using 255.255.255.0 subnet will tell your PC to send packets not in the 10.0.1.xxx subnet to the router at 10.0.0.1 to be routed to another subnet.

mk42 · Jun 30, 2016

Archie said:
If there is a gateway/router, then you will need to know its address. It could be the 10.0.0.1 address. Try setting your subnet mask to 255.255.255.0

Using 255.255.255.0 subnet will tell your PC to send packets not in the 10.0.1.xxx subnet to the router at 10.0.0.1 to be routed to another subnet.

If he's using the 255.255.255.0 subnet with an IP address of 10.0.1.1, then the router would need to be in the same subnet, not in 10.0.0.x.

Ultimately, you're going to need to ask the IT guy, because the correct settings for the IP addresses depend entirely on how the network is laid out.

Archie · Jun 30, 2016

mk42 said:
If he's using the 255.255.255.0 subnet with an IP address of 10.0.1.1, then the router would need to be in the same subnet, not in 10.0.0.x

you are correct. I missed that detail.

sparkie · Jul 2, 2016

Well, we can make this even more simple if necessary.

Ask your IT guy what the IP of the default gateway is. Put this gateway IP in the PLC configuration.

Find out if all of these are connected to the same switch and let us know.

Operaghost · Jul 3, 2016

But for the IP addresses mentioned, a gateway or router is not required. Your subnet masks are a little out of control though.

The subnet mask for the computer allows up to 1022 devices. The subnet for your PLCs allows up to 4094 devices. I wouldn't expect an IT guy worth his salt to allow that. That is a lot of potential broadcast traffic.

You haven't said if this worked or did not. Is the PC able to ping the PLC?

OG

gbradley · Jul 7, 2016

I don't know if the Sonic wall is what you call a gateway router, but I believe that it is what assigns the IP addresses for the PC's.
The Subnet of the PC is actually Subnet mask: 255.255.252.0
I set the IP address for the PLC from the front panel.
The problem is when I was trying to Remote in, I couldn't see the PC on the other side of the switch.
I think that the problem is with the Sonic wall appliance.
I've got the IT guy working on it.

Thanks

IP Addressing Office to Shop

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