1769 Extra Subnet Comms

Hi,

I've got a 1769 controller which is talking to various different components on a local network, I want this controller to talk to another AB PLC via the MSG instruction, however this PLC is on a different subnet.

Example - current PLC is 192.168.1.1, the PLC which I want to MSG is 192.168.2.1.

Although the PLC is a 1769-L30ERMS, and it has two Ethernet Ports, I don't believe that you can set them up to be on two different subnets.

Would it be a 1769-AENTR module which I need to get to do what I want to do?

My Network switches are unmanaged.

Thanks

The 1769-AENTR is an adapter for 1769 modules.

If you make the subnet mask 255.255.0.0 you should be able to message between the 2 PLC's.

Alan.

alan_505 said:

The 1769-AENTR is an adapter for 1769 modules.

If you make the subnet mask 255.255.0.0 you should be able to message between the 2 PLC's.

Alan.

Click to expand...

But the other PLC is not in this PLC local subnet, so I definitely need something to communicate across subnets, are you saying that the 1769-AENTR isn't what I'm looking for?

The 1769-AENTR can only be used to connect 1769 IO modules to a ControlLogix or CompactLogix processors.

If one PLC is 172.168.1.1 and the other is 192.168.2.1 then you can message between them by using the 255.255.0.0 subnet mask, but they must be physically connected together.

They should be able to be connected through an unmanaged switch.

Alan.

What do you mean by subnets?

alan_505 said:

The 1769-AENTR can only be used to connect 1769 IO modules to a ControlLogix or CompactLogix processors.

If one PLC is 172.168.1.1 and the other is 192.168.2.1 then you can message between them by using the 255.255.0.0 subnet mask, but they must be physically connected together.

They should be able to be connected through an unmanaged switch.

Alan.

What do you mean by subnets?

Click to expand...

I never realised that PLCs could do that, so as long as my subnet mask is 255.255. 0.0 that means that the first two octets have to be the same, ie 192.168, but the third and fourth octet can be different, so my PLC could be 192.168.1.1 and PLC which I message could be 192.168.200.1 if I wanted?



Cool, I always thought that to go outside of the third octet I'd need some sort of additional comms module!


Thanks for the help, I shall give it a go.

There is a difference between two logical IP subnets on the same physical/logical LAN (ethernet network connected by switches or hubs or repeaters, a.k.a. ethernet broadcast domain), and two IP subnets separated by an IP router or gateway.


If the two cards are part of the same broadcast domain with only switches and no gateways between them, then modifying the mask to make the part of the same subnet should work.


For 192.168.1.x and 192.169.2.x on the same logical LAN, you could also get away with a mask of 255.255.252.0.

drbitboy said:

There is a difference between two logical IP subnets on the same physical/logical LAN (ethernet network connected by switches or hubs or repeaters, a.k.a. ethernet broadcast domain), and two IP subnets separated by an IP router or gateway.


If the two cards are part of the same broadcast domain with only switches and no gateways between them, then modifying the mask to make the part of the same subnet should work.


For 192.168.1.x and 192.169.2.x on the same logical LAN, you could also get away with a mask of 255.255.252.0.

Click to expand...

Great, thanks for the clarification.

Jackllx said:

Great, thanks for the clarification.

Click to expand...

You're welcome.


https://www.youtube.com/watch?v=jg1mYsIrFPs&t=61s