VPNs & IPX

I have a customer with a plant some 40+ miles away from his office and I need to have a PLC in his office (DL06) communicating with a PLC at the plant (250-1). Both PLCs will have an ECOM, but neither ECOM will have an IP address (existing systems and backwards compatibility).

There is a mountain between the plant and office so wireless radios are definitely out of the question.

High speed internet exists at the plant and at the office so my first thought is to put a hardware VPN in place to "bridge" the two networks, but I've only ever used VPNs with IP networks (here its IPX) and then only to connect to a PLC via DirectSoft. Has anyone done something like this before? If so what hardware did you use and how successful was it?

Is there a gsm (cellphone) network available at both ends?

Probably, though mobile phone reception inside the plant will be unreliable at best. We're trying to figure a way to do this without incurring any new monthly recurring charges.

Not sure you can get away from adding some new monthly charges. You may need to obtain static IPs at both locations to setup communications through the internet. I would suggest using VPN; http://computer.howstuffworks.com/vpn.htm

Both PLCs will have an ECOM, but neither ECOM will have an IP address (existing systems and backwards compatibility).

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I do not understand this part, you have Ethernet communication cards but can't or won't use them?

IP and IPX can co-exist on the same network. We have a Novell server and regular internet router here for our office.

I have the same question for our people to VPN into our server, and have not been able to answer it.

For you, can you set up an IP network only to the PLC? I did not think that any talked IPX.

Both PLCs are part of standard OEM products that we sell. We have always used IPX comms between our various products because module ID configuration is easy with the DIP switches and many of our end users do not have access to a computer.

I could setup IPs on these ECOMs, but that creates 1 user out of many that is now unique which is a bad thing from a troubleshooting / support standpoint. At some point down the road one of the ECOMs may fail, or get robbed to replace an ECOM in a more important PLC in the plant and it is highly likely that the person working on the equipment won't know this particular one was setup with IPs or even have the tools to change the IPs.

Mark, my apologies first, I do not understand what you want and some of my thoughts may sound condescending.

At some point down the road one of the ECOMs may fail, or get robbed to replace an ECOM in a more important PLC

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This is a bad method of maintenance in my opinion but of course necessity may dictate the situation.

What you may be have to do is use 2 separate PLCs with ECOMMs to setup the communication and make it known that is what they are for and not to be used on the machines. This should allow you to setup VPN and use IPX.

rsdoran said:

Mark, my apologies first, I do not understand what you want and some of my thoughts may sound condescending.

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No need to apologize to me. I'm always open to ideas and I know this particular application has got to sound screw-ball at best. Most of our customers do not have anyone on staff that can troubleshoot more than mechanical failures. Hydraulics, belts, motors, etc, are all easy for our customers, but anything related to a PLC, network, computer, etc is difficult for them and usually the best we can get is them acting as our hands and eyes to do some part swapping while we sit on the phone.

Since we are an OEM and we supply products to our end customers one of the things we attempt to do is never have custom software or PLC setups for a particular customer. The reason is simple compatibility and upgradability. If I find a bug (or add a feature) while visiting a plant I have the ability to make a new software version and load it onto any other customer's same model machine anywhere in the world without writing any more code. I can also send it to our other engineers that are not as proficient in PLCs and have them load it without the need for them to understand the intricacies of how the new software works. Our current system of IPX communications between our machines allows even the non-computer / PLC / network literate person to flip some dip switches on an ECOM card (looking at a picture in the manual) and instantly have communications that work.

Hmm.. after re-reading that I don't know that I've made anything clearer for ya... hmm...

I got the gist of it, its a dang if you do or dang if you don't situation.

Necessity dictates the situation in most cases, this may be a situation where you may have to do something that you ordinarily wouldn't.

Using the internet appears to be the logical choice for a low cost solution. Leased phone lines would probably work but that can be expensive.

I had a few too many last night so can not think too clear right now, let me think on it and I will come back if the light comes on.

You've got it... I don't mind the special setup on this one, but I'd rather it be special hardware added to the existing system design and not special settings in the "normal" system components. Then in the future if it breaks its much more obvious that this was a special setup...

Changing the direction a little bit. Anyone know of good, reliable, VPN hardware? Price is important, but not critical. My idea is a box between the plant network and the internet and a box between the office network and the internet and those boxes allow IPX comms to flow from plant network to office network and office network to plant network and don't interfere with normal internet traffic in and out of the office network or plant network.

Ya might want to call Cisco and ask them to talk to you about VPN concentrators that'll handle IPX.

If I were you I would still look at wireless. I have wireless systems working perfectly without line of sight and without repeaters. Of course I’m not using the license free (900MHz) frequencies, they don’t work over mountains, at least not without repeaters. You might be able to get a wireless link with a low frequency, say somewhere around 150MHz. You’ll need to get a license from the FCC to operate in that frequency, but the cost of an FCC license, radios, and antennas costs less than radios that operate in the license free frequencies. And if a direct link won’t work, you can always use a repeater.

But if your still hooked on the internet idea (which generally isn’t a good idea), take a look at Linksys’s RV0041, RV016, RV042, or RV082 VPN routers. They are easy to set-up, they offer different types of VPN, and you can set-up the routers to make the VPN connection between themselves.

Here is the link to Host Engineering (the company responsible for the ECOM modules) take a look at FAQ0016, it details how to make ECOM connections over the Internet.

http://www.hosteng.com/hw-products/ecom/ecom.htm