CompactLogix L32E and 1734-AENT in different networks

[Tarlo]

Hi all, i have a CompactLogix L32e and a network module 1734-aent. I've made an ethernet connection on the same network (with an hub) and all works.
Now I'm trying to put the PLC in a different network from the 1734-AENT module (on the same hub) but I can not make them communicate with each other.
For example i would to put the L32 in a network with ip 10.12.0.100 and the module in a network 10.10.0.90 with both subnet mask 255.255.255.0 but the plc doesn't see the module.
I have set up even the gateway in both devices with their respective ip but doesn't work.
How can i do?

Thank you all.

 

[Hydro Power Guy]

Not possible with a hub. I guess you can probably do it if you have a router and set up a custom routing table.

 

[TJS]

That subnet mask will stop the IP packets from arriving. I think if you changed the subnets to 255.0.0.0 then the 2nd octets .10. and .12. would be permitted to see each other. I may be wrong about the Private Network class of a 10. network (is 10. Class A, B or C?) so the 255.0.0.0 subnet may not be allowed.

Otherwise as the other guy said you'll need ant IT person to maybe create a couple gateways (10.10.0.1 and 10.12.0.1 for example) and associated router rules to allow packets to travel between these 2 private networks.

Beware the 255.0.0.0 subnet opens up the broadcast address (10.10.0.255, and 10.12.0.255) to like a bagillion possible destinations IPs. Much smarter to use 255.255.255.242 for example to limit network traffic to a small group of maximum 16 IPs/nodes (limit valid traffic to only the local group such as PLC1, PLC 2, HMI1, OIT1, ScadaServer1 and not the entire world)

 

[daba]

That subnet mask will stop the IP packets from arriving. I think if you changed the subnets to 255.0.0.0 then the 2nd octets .10. and .12. would be permitted to see each other. I may be wrong about the Private Network class of a 10. network (is 10. Class A, B or C?) so the 255.0.0.0 subnet may not be allowed.

Otherwise as the other guy said you'll need ant IT person to maybe create a couple gateways (10.10.0.1 and 10.12.0.1 for example) and associated router rules to allow packets to travel between these 2 private networks.

Beware the 255.0.0.0 subnet opens up the broadcast address (10.10.0.255, and 10.12.0.255) to like a bagillion possible destinations IPs. Much smarter to use 255.255.255.242 for example to limit network traffic to a small group of maximum 16 IPs/nodes (limit valid traffic to only the local group such as PLC1, PLC 2, HMI1, OIT1, ScadaServer1 and not the entire world)

Well some of what you said was correct, but some not.

If the network in question is not connected to the internet, (and of course most are not), then we do not have to worry about IP classes - we can use any IP address scheme we wish.

An IP address 10.xx.xx.xx is class A, but only when we intend it to be "classfull", i.e. when we want to expose it to the Internet

Private networks don't need to be "classfull", so the question of whether 10.x.x.x is class A, B, or C, when used on a private network is irrelevant - they are only numbers, i.e. the private address can be "classless".

You cannot just make up some arbitrary addresses and connect to the internet - internet IP addresses are assigned to you/your organisation by ICANN http://www.icann.org/en/participate/what-icann-do.html

The internet does not use subnet masking, that is only for private networks, and provides a more realistic control of node/host ratio than the class system allows.

The downfall of the original IP class system is that it didn't predict the level of usage that we see now, and it's specification was wasteful, which is the major reason that the system is being updated to IP V6

 

[rdrast]

All of which begs the question:

Why in the world would you want to put your CONTROLLER and your IO on separate networks? I can envision absolutely no situation where that is even remotely a good idea.

 

[Tarlo]

Thank you all for the answers.

Why in the world would you want to put your CONTROLLER and your IO on separate networks? I can envision absolutely no situation where that is even remotely a good idea.

Well there's no reason for put the controller and IO in different networks but i am experimenting how to do because i'll have to put two controllers in different networks but for now i have these components for try this.

I've got a digicom router. I connected my PC, the IO and the controller to the router. I set the controller's ip as 10.12.0.100 (subnet 255.255.255.0), the IO's ip as 10.10.0.90 (subnet 255.255.255.0). I log into the router and i go to set the routing tables but he does not accept the ip assigned to the IO and controller as gateway ip giving me the error: "Please check that the gateway is a valid remote node IP address".

How do I set the router?

Thank you all again.