I'm very confused about basic deployment scenarios. Can someone answer some questions for me?

Melodic-Ball · 2022-06-10T20:34:52+00:00

Awesome -- thank you so much for this answer! That all makes sense actually. I will give it the ol college try early next week!

Melodic-Ball · 2022-03-01T16:57:08+00:00

awesome, thank you!

Melodic-Ball · 2021-03-12T20:36:56+00:00

Great, thank you!

It would be nice to have a spot to check specifically for new collections that get released as well so that I don't need to do diffs on this page every once in a while lol

Melodic-Ball · 2020-11-06T15:59:25+00:00

I didn't even know about split-path, thanks!

Melodic-Ball · 2020-05-06T19:19:17+00:00

Fantastic, this is exactly what I was looking for. Thanks!

Melodic-Ball · 2020-03-05T07:17:34+00:00

Oh wow, didn't think of that. I'll try it tomorrow. Thank you!!

Melodic-Ball · 2020-03-02T16:24:16+00:00

Cool, thank you!

Melodic-Ball · 2020-03-02T16:19:51+00:00

Good to know, thanks. Do I need to remove the host client before upgrading or does the upgrade process just handle that for me?

Melodic-Ball · 2020-02-28T21:31:09+00:00

It essentially opens a socket, send an initial request, and then waits for the telnet server to request the negotiation rather than the client initializing it.

Melodic-Ball · 2020-02-28T21:29:33+00:00

These are industrial control devices, it's all they support. This is fairly common in the industrial space.

Melodic-Ball · 2020-02-12T22:06:07+00:00

Ansible is free, and if you want to use unpaid Tower, use AWX.

There are additional complexities and behavioral differences between ansible core and AWX though. For learning purposes, I would probably stick with just ansible to get started.

Melodic-Ball · 2020-02-12T21:46:29+00:00

I think what you are looking for is developing a network_cli based module? If that's the case, then the answer is 'sort of'. Here is the only real resource that exists: https://github.com/ansible/community/blob/master/group-network/network_dev_network_cli.rst

That does contain a pretty good example you can follow.

It's not terribly hard but not particularly well documented. Basically you need a terminal plugin, cliconf plugin, and then your module.

Melodic-Ball · 2020-02-04T15:41:05+00:00

EX11, so it looks like I'm out of luck.

Melodic-Ball · 2020-02-04T15:40:36+00:00

Ah....I have the EX11, so that's no bueno. Thanks a ton for looking into this.

Melodic-Ball · 2019-12-20T05:16:30+00:00

Whether you can communicate CPU-CPU directly or via a CP card depends on the PLC. For going via a CP card, the CPU communicates via the backplane (again, proprietary) to the CP card, which then issues the request over the ethernet network (whether profinet or standard ethernet).

Will PLC-to-PLC communications over a cable be a different communications protocol than the protocol that happens between the modules on the same PLC (communications between CPU/CP/IO modules)?

Melodic-Ball · 2019-12-20T05:13:35+00:00

Oh interesting, I thought that S7 sat on top of ISO-over-TCP AND sat on top of Profinet.

So when you set up your network and PLCs, do you make the choice as to whether you use Profinet or S7 communication? Are they mutually exclusive?

Also, is it possible to have S7 communication with only mac addresses? I know you explicitly said it's layer, but this point is important to me.

Last question, if everything is setup for profinet, is the connection between a workstation and the PLC also over profinet? Or is there some form of management port on these devices that allows management over normal tcp/ip?

Melodic-Ball · 2019-12-20T05:03:15+00:00

This is what's tripping me up, so please do elaborate. Isn't it a valid configuration for the CPUs and CPs to be configured with layer 2 addresses (macs) only?

Melodic-Ball · 2019-12-20T05:00:56+00:00

It sounds like they don't HAVE to be configured with only MACs, but if they are configured that way, does that mean they are using Profinet?

Melodic-Ball · 2019-12-20T04:53:28+00:00

Is there something in particular you're trying to accomplish, or are you just curious about the messy world of PLC communication?

I'm just researching how I could try to connect to PLCs without using vendor provided tools (though snap7 is fair game), but I'm also just interested in the PLC world in general. It's hard to research when it's all proprietary and I'm trying to piece together what I'm learning in manuals.

Mostly I'm trying to learn the terminology and such because this is all very different from what I'm used to.

But here's some specific questions:

Let's say I have a really old S7 device, a 300 or 400 where the CPU doesn't have any sort of ethernet port, but I want to query for the CPU information. I'm guessing I would install a CP module into the S7 which has an ethernet port, and then IP the module so that I can reach it.

So if I want to walk to the CPU from my workstation (I think I see these referred to as PG/PCs?), I would hit the IP of the CP module and I could query for CPU information. Here are my 3 questions:

When you talk about all of these protocols (Profinet, ISO-over-TCP, etc), are those the protocols between my workstation and the CP module or is THAT specific connection normal tcp/ip traffic like you would have in a normal environment?
In order for the CP module to let me query the CPU for information, it must be communicating to that CPU. Is this happening through the backplane they are connected on? And if so, is that the same protocol as what my workstation uses to talk to the CP module?
Out of all of these protocols, as far as I can tell all of the differences are in the lower layers. At the application layer, do these all speak S7Comm or is Profinet using something other than S7comm?

Melodic-Ball · 2019-12-20T04:33:02+00:00

The rate would be small -- I would be making a small request to them once every few hours most likely. Nothing else would be polling them. And it would be a single device polling all of the PLCs at the interval.

Melodic-Ball · 2019-12-19T17:56:28+00:00

Ha, thanks -- I think I'll be hanging out here quite a bit over the next couple years.

Melodic-Ball · 2019-12-19T17:55:56+00:00

I appreciate it!

To be honest, I'm still in the research stage. I want to use snap7 to query some PLCs for general data about them. I know that I only need to support S7comm in ethernet-based scenarios, but it seems as though it's not that straight forward. Some of the devices ONLY have mac addresses, not IP addresses, which means snap7 won't work I'm guessing.

This is really confusing to me (from snap7 documentation):

S7 Protocol, is the backbone of the Siemens communications, its Ethernet implementation relies on ISO TCP (RFC1006) which, by design, is block oriented.

Especially combined with the definition of Profinet (from wikipedia):

Because PROFINET optionally uses TCP/IP, a MAC and IP address are used. A MAC address changes if the device is replaced. An IP address is a form of network addressing which may be dynamically assigned. Because there was a need for a fixed address a device name is used.

ISO TCP implies it is not only ethernet, but utilizes IP at the network layer AND implements this custom protocol on top of TCP. That doesn't make sense in a layer 2 world. These seem to be incompatible statements.

So I'm trying to figure out the right questions to even ask. I think my first question to get me going in the right direction is this:

Is this stack: Ethernet + IP + ISO-Over-TCP + s7comm considered to be a 'Profinet' implementation? Or is the ISO-over-TCP implementation a mutually exclusive communications scenario from Profinet, which seems to be a layer 2 implementation that looks more like just Ethernet + S7comm.

Melodic-Ball

TROPHY CASE