AB plc ethernet / router comms

[ian.smith7]

Hi
In our factory we have 10 or more control panels, most of these use AB plcs and ethernet for local comms (mostly SLC 5/03 and above with a couple of CLX and PV+ HMIs). However they have very different IP address ranges. Some of our maintenance guys have trouble getting the laptop(s) comms adjusted to connect into these local networks.
I have suggested fitting routers to all the panels so that reconfiguring the laptop for each panel is not required and also as a first step towards installing a factory scada system.
So now I have been asked to spec and price the routers (Me and my big mouth!). I would appreciate some help to do this as although I understand what a router does I have no practical experience using them.
Does any one have a recomended router for use in this situation?
What specifications are required for the router to operate with the scada system (which will be a standalone network running windows / AB software)?
Thanks for any help or advice
cheers
ian

 

[Paullys50]

Take a step back.

Before even thinking about purchasing equipment put your thoughts on paper.

First you need to plan out your IP addressing scheme, and implement it before networking them together.

For example, think of a home network that uses 192.168.Y.X addressing, use this as a template for your network. The subent is 255.255.0.0 in these beginning steps.

Y = Machine group number
X = Equipment number

So, lets say you have 10 pieces of equipment, each will be assigned a machine group number (1 - 10) and will have a single PLC and HMI.

The PLC will have an equipment number of 2, the HMI will be 3.

So on machine 1, the IP Address are:
PLC: 192.168.1.2
HMI: 192.168.1.3

Machine 2:
PLC: 192.168.2.2
HMI: 192.168.2.3
.
.
.
Machine 10:
PLC: 192.168.10.2
HMI: 192.168.10.3

Doing it this way leaves plenty of IP addresses for each system, as well as it keeps it organized.

Once you've got that figured out and on paper, begin to reconfigure all the existing systems with the new IP and Subnet settings. Once that is complete, move to adding a SWITCH at each system. This switch would be managed, and is configured as the gateway for that particular system, the gateway will allow the equipment within that system access to the outside world, a-la another system in the 192.168.Y.X range. The switch is given an equipment ID of 1. So it's IP address is 192.168.Y.1 for each system.

Now, you can begin to consider how to tie each system to the other. Here is where the IT department probably will want to pitch in their two cents especially if you want to use the corporate network to get to the PLC network.

That is a general starting point, proper planning now will prevent nightmares and added costs in the future, definitely get your IT department involved for more guidence.

 

[Paullys50]

Note -

Before you begin to change your IP addresses on your existing systems, be sure you understand the PLC/HMI program changes you may need to consider to prevent communication losses do to the IP change. Especially if you have remote I/O on ethernet or are using produced/consumed tags.

 

[Operaghost]

I think what the OP is suggesting is that he puts a router (or specifically a box that can do DHCP) on each panel. Not necessarily connecting them all together. Then the techs can plug the computer into a panel and automatically get assigned the right IP address for that box. It's not a bad idea as a quick fix. Changing IP addresses on the PLCs can have wide ranging consequences.

I'm not sure of your environmental needs but basically you just need the equivalent to a cheap home "router". A switch that can do DHCP serving.

If the ethernet switches in the panels are industrial managed switches, that capability might already be there. Do you need an industrial switch? What switch is currently in the panels.

OG

 

[Paullys50]

It's all about perspective I guess. In my opinion multiple machines with unorganized IP addressing is just asking for troubles in the long run especially if equipment will continue to be added, as the OP takes their next step to a SCADA system everything will begin to be networked together anyway, a structured IP addressing scheme will be a blessing.

Establish the factory's IP address structure now and require that to be followed by integrators/OEM's as new equipment is installed. As the SCADA system progresses add a Domain Controller to handle DHCP. In the mean time a single router should due as long as each machine switch is connected to the router. It doesn't make sense to me to purchase routers for every control cabinet if a true SCADA system is a goal for the facility.

But just like anything else, there are all kinds of paths you can take, I guess my point is understand what your needs will be in 5 - 10yrs and plan for it now while it's easy.

 

[OZEE]

But even with putting in a router, youll still have to know the IP addresses of the existing plcs and panelviews so you can get the DHCP all setup correctly. It won't be hard - you just need to follow Paully's first advice:

Take a step back.

Before even thinking about purchasing equipment put your thoughts on paper.

IF you just go sticking in a router to DHCP the maintenance PC's into the network, there is no guaranteeing that they'll work if you don't understand how the rest of the network is configured.

 

[Operaghost]

I agree that Paullys initial response was dead on as to what SHOULD be done.

The router setup would only need to dole out IP addresses to the PCs, not the PLCs or HMIs. However, the RSLinx setup would end up being the real issue.

If you created a separate Ethernet driver for each panel that would make it easier. When browsing, just select the driver with the name that identifies that particular panel.

Again, I agree that Paully's approach is the right answer in the long run.

OG

 

[ian.smith7]

Thanks for your replies
The IP addressing of the PLC Networks will remain the same as it is now.
I was hoping to use fixed IP address ranges for the in and out ports of the router this would allow me to fix the laptop IP addresses in the same range as the out port, with a subnet of 255.255.255.0. This would mean no config changes to Laptop for different panels and no changes to the existing PLC programs.
I was a bit nervous about using 'Home' style routers for this as they may not handle all the protocols/config required for a future SCADA.
Two outward facing ports would be an advantage (SCADA + Laptop). Is this possible?

The existing switches are of various types some small some large. I think Standardising the routers would make things easier for me and other users.

I thought remote subnet browsing to (fixed?) IP addresses (ranges?) could be configured in one of the two IP drivers in RSLinx?

any further advice on router hardware would be welcome.
cheers
ian

 

[bulletin blues]

Would writing some NETSH.bat files help? Do a search for netsh on this site. I'm not sure if the problem is with the assigning of IP addresses or the Logix side of this from your post.
There are a lot of considerations before diving into this. You might want to look into the following before committing to anything.
Layer 3 switching.
Vlans.
Dynamic VTP.

 

[ian.smith7]

Hi
There is not a problem, We already use both ethernet and serial comms to connect locally into the PLC's but the IP address ranges used in the panels all vary. Some are 192.168.1.xxx another panel uses 168.20.1.xxx (8 different ranges in all). I Want to use the routers to allow any of our maintenace guys to turn up at any panel and communicate with the local network with either of our two laptops without having to reconfigure the laptop network card.
I would like to achieve this without altering in any way the existing PLC or HMI programs. Initially this access will only be used to monitor, Upload and Download with occaisional online edits.
In the future we would like to run a network back to our workshop for data logging and SCADA. So my main concern is to buy routers that would do this.
I could buy some of the shelf cheap domestic routers but I am concerned they will not be suitable for our future plans. So I would appreciate some specific examples of routers used in PLC SCADA systems then I could look at their specs and prices. Because I am not familiar with SCADA systems I am not sure if they require any "special" ethernet routing abilities.

I hope this Clarifies my question a bit more.
cheers Ian

 

[MannyM]

I have learned something here.

Control system & factory management, integrated at a very system control level, creating a logical factory system that will be applicable in future. This should filter down to the documentation level as well.

The way your first respondent sets it out from a ethernet & factory management control system, makes absolute sense. From a factory maintenance point of view, you need this network & logical IP addressing to enable a control system management system, MDT. This is existing.

To change certain IP addresses on any PLC (whether controller or bridge) and any HMI work station, needs a comms break between the respective units where applied.

The HMI, production line control, no problem. Management views will be interrupted as well for the spesific line.

Higher levels of HMI should be able to have an acknowledgement of the incident prior to executing. This can be done by the heart of the controls, the PLC.

To change the PLC or bridge IP address, will need a total shutdown of the production line. Much more manageable and predicted responses, if any. It allows a window of time. Much safer as well.

Independent of the higher level of networking, routers etc.

 

[mellis]

Random IP addresses are a problem. Reconfiguring the laptop network cards is a hassle but it's not the real problem. If all you want to do is make it easy to connect to your 8 different IP ranges how about buying 8 cheap USB ethernet NICs? Configure one to each IP range, just plug in the one that matches the network you want to work on. A *lot* simpler than routers.

Changing the IP addresses on the PLCs and HMIs is not that big of a task. Paully's5.0 approach is a good one. Plan it out and execute it, problem solved. It may take time to get it all done, but you end up with a network that is easy to understand and work with. If there is no PLC to PLC messaging over ethernet it should be simple to execute one PLC at a time.

Adding routers only complicates the system. Routers are not an antidote for bad network planning.

In answer to your question about "special" ethernet routing abilities: The SCADA systems I have worked with don't use routers at all. Managed and unmanaged switches are common, but I've never seen anyone use a router in a SCADA system. Not saying it can't be done, but it is certainly not common.

One "special" sistuation you should watch out for as you combine these smaller networks is I/O over EthernetIP. If you have any networks using I/O devices over EthernetIP, you will want to either keep them isolated or use a properly configured managed switch to limit the multicast traffic.

Good luck.

 

[ian.smith7]

yes your right poor planning is to blame for this problem, five different contractors (possibly more) were used to build this intergrated production line. Each was allowed to use any IP address range they wanted. Virtually all the control panels on site use ethernet for local HMI/PLC/PLC comms.
Maybe it would be best to change all the panels to the same IP address range.
Maybe my assumption that using a router in every panel would isolate each seperate network whilst providing a common IP access range was a compicated solution to a "simple" problem. The Plant is three years old and some OEMs are still involved in solving "issues". A "Hands off" solution for some control panels seems preferable to me.
Sorry, that sounds like whining as I read it through.
Would installing routers and setting up some fixed IP adressing tables really be a big problem?
ian