Linking two plc together with two different ip address

stu

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Join Date
Aug 2005
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England
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772
Hi guys
I have 2 machines with Allen Bradley plc one is compactlogix and the other is a mircologix all on Ethernet, I would like to commuicate from one to the other ( they are on different networks ) is there any way I can do this without changing the ip. Thanks
 
They need to be different IP addresses or they will not communicate.
What are the IP's?
If the first or first two octets are the same or close you may be able to use just the masks. i.e. 200.0.0.0 or 255.200.0.0.
Else go through a router.
 
The ips 192.168.0.1 sub 255.255.255.0 2nd 192.168.1.13 sub 255.255.255.0,
1 on a flour system and the other is on a mixer, we a trying to make it work together in sequence??
 
Change your subnet masks to 255.255.0.0 and provided they're physically on the same network (via a switch or router) you should be able to ping each machine.

A picture of your physical network layout would be a useful thing to have too.
 
Change your subnet masks to 255.255.0.0 and provided they're physically on the same network (via a switch or router) you should be able to ping each machine.

A picture of your physical network layout would be a useful thing to have too.

Make sure, as I recall, all the intervening routers/managed switches do the same thing as well.
 
Changing the subnet masks does not always work.
Some PLCs (Siemens for sure, others are more flexible) will refuse a 255.255.0.0 subnet mask if you are on the 192.168.x.x ip address range. Technically, you are supposed to use a mask of 255.255.255.0 on the 192 range. It may work though, and I have got it working on some equipment.

If this is a problem, try the 10.1.x.x if you need to use a larger mask.
 
Make it a /23 network or a mask of 255.255.254.0 on both units and it will work.

Just a few devices masking it will be fine.

There were some above comments about a managed switch and just to clarify a managed switch does not mean it will serve as a router. Some do and some don't.
 
Make it a /23 network or a mask of 255.255.254.0 on both units and it will work.

Just a few devices masking it will be fine.

There were some above comments about a managed switch and just to clarify a managed switch does not mean it will serve as a router. Some do and some don't.

I mentioned the managed router as something you'd have to change the subnet mask on, as opposed to unmanaged switches.

So, I think, to summarize this thread: If you can change the subnet masks, great! If not, look into some form of router to NAT for you.
 
I mentioned the managed router as something you'd have to change the subnet mask on

Not necessarily. A managed switch will still switch packets even if it's management interface is set to a different subnet.


So, I think, to summarize this thread: If you can change the subnet masks, great! If not, look into some form of router to NAT for you.

No you would need something to layer 3 route not NAT. These are different things.
 
If I use a managed switch, could I uses the tag names from the each plc program
To use the names you will need a DNS somewhere and a lot of "industrial" equipment does not play well with them.
 
To use the names you will need a DNS somewhere and a lot of "industrial" equipment does not play well with them.

Russ I think he ws asking about program tag names. You must be thinking about hostnames / Domain names which is the only thing you would need a DNS for.
 

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