obtain IP address automatically option

[realolman]

I just got a dlink pocket wireless ethernet router/AP

http://www.amazon.com/D-Link-WIRELE...y/dp/B005RCVDW0/ref=sr_1_6?ie=UTF8&qid=132766

I had it hooked up yesterday for the first time and it IS nice I can get the whole way around three large machines with the laptop.

I had to change the local area connections IP address in my computer and the router to be compatible with the network of the three machines. I have to do this every time I want to connect to a different machine or the company network.

Is there a way I don't have to do this. what is the obtain IP address automatically option for? It is available on both the laptop and the router/AP.

I have had a great deal of aggravation with IP addresses because many times they are not known or whatever. What burns me up is that the computer HAS to be doing some sort of communication with the connected device (panel view etc )because the Network Icon in the taskbar lights up and says it is connected at 100Mbps or whatever it is.

What is the "obtain IP address automatically option" for? thank you

 

[rdrast]

Obtain address automatically just tells your computer to look for an address assigned from a DHCP server on the network, which your router is probably acting as.
I don't know what else is on your network, but having multiple DHCP servers is not a good idea, and I always disable the server in every device that I plug in, and use static addresses everywhere.

If you manually assign addresses (in Windows), you can set up alternate addresses, and effectively be on two (or more) networks at one time.

 

[RussB]

With the little information you have given so far it would be impossible to say for sure but try looking at the IP addresses used by your work cells. You may be able to change the mask in your laptop to something like 255.255.0.0 to make it work.
Or worse case get one of the free "IP juggling" apps from the 'net. Many have been discussed on the forum in the past.

 

[realolman]

I have the computer set to obtain IP addresses automatically when I am not hooked to a PLC, for the plant's network. There are several different IP addresses for various machines in the plant, so I have to set the computer to the same "network" as those to talk to them. Now that I have the wireless link device I also have to change it.

I got one computer connected to one Panel view....Why can't this stuff determine what IP "network" it is connected to? As I said earlier it has to be doing some kind of communicating because as soon as I connect up a cord, the little network icon lights up and it knows how fast the connection is. When I have one device hooked up ( a panel view, a PLC etc ), how does it know how fast it is, but it doesn't know it's IP address?

 

[RussB]

That could be done, however it would need to know every IP on the network so it did not select a duplicate and mess up the whole network. Have you tried using the "alternate" IP address?

 

[iant]

most PLC's that run on e/net do not or rather can not use DHCP (automatic asignment of IP addresses)
You need to configure the router to a static address in the range of your PLC network both IP and Mask
Then set the notebook IP addrress to the same IP addrress area and subnet mask.
then you will be able to access all components on the network

DHCP on the notebook also needs to be disabled

 

[The Plc Kid]

DHCP will work on many ethernet plc's. Ifit is used though I would recommend setting up a DHCP reservation. This is where in the DHCP server you tell what IP address to use based on the devices MAC ID. All ethernet devices have a unique MAC ID and this way it will get the same address each time. Most all routers have this even the consumer type and if they don't then install DD-WRT http://www.dd-wrt.com/site/index

 

[The Plc Kid]

You could also setup static routing in the router also. Make a static route for traffic to go from 192.168.1.0/24 to 10.10.90.0/24 for example. Your plc and drives may be on 10.10.90.0 network and your laptop on the 192.168.1.0 network but with this route they will communicate.

 

[realolman]

That could be done, however it would need to know every IP on the network so it did not select a duplicate and mess up the whole network. Have you tried using the "alternate" IP address?

If I have the wireless disabled on the laptop, and I connect a single Panelview with a cord, the little network connection icon lights up and says something to the effect of

"Network connected"
"speed 54Mbps"

Now... it is not important to me exactly what it says or what the speed is... what I don't understand is:

how exactly does the laptop know that it is connected and what the speed is, but at the same time it doesn't know the IP address of the single connected Panelview?

Exactly what communication between the panelview and my laptop has been performed that it knows as much as it is telling me that it knows?

I have a feeling my laptop knows more than it is telling me

 

[nwboson]

The "Network Connected" means the wifi has successfully connected - the physical link has been established, but that does NOT mean you have an IP address.

For your PC to automatically get an IP address, some device on that network must have a DHCP server setup to hand out IP addresses within the range of addresses defined for that network (the network mask defines the range).

Many industrial networks contain no DHCP server - most industrial networks contain no router. I feel strongly that industrial networks should NEVER contain a DHCP server. This ensures that someone who inadvertently connects to that network cannot talk over the network (and screw up the comms between devices) - they must know how to set a static IP on their PC/laptop to talk over the network. That helps ensure only qualified folks connect to the industrial network.

Your pocket dlink (or most off-the-shelf access points) is setup to act as a switch and picks an arbitrary range of addresses for it to use - the chances are very slim that it picked the same range already defined for your PLC network. So you need to change the APs address to get within the range someone predefined for the PLC. Some APs can be configured as a 'bridge' to force it to act like a stupid switch which would save you from having to reprogram the AP: but you would still need to know a valid address within that PLCs range and set a static IP on your PC in any case, unless a DHCP server is present.

The 'obtain IP address automatically' on your PC means that you give your PC permission to act as a DHCP client: "please, Mr. PC, go get an IP address automatically from the network's DHCP server". But without a DHCP server setup in that range of your PLC, your PC will forever wait for a DHCP server to provide that address. Its amazingly patient though...

 

[The Plc Kid]

To add if you are talking of a wired connection then the nic senses the change in resistance on the wiring but this does not mean it is really plugged in as that circuit is easily foolde and many times driver issue of the nic will show it connected when it is not.

As far as DHCP I low it and use it for auto device replacement. Helps bubba get the line running and I don't get called in at 2:00 AM.

AS far as DHCP to my laptop I lock it down by MAC ID so only company E&I laptops will be given a address from the pool.

All unused ports in all switches are blocked / locked and the only programming port is the grace port on the front of the panel.

We have no problems with keeping unqualified people of our machine networks because we have lots of cameras and we don't mind firing people.

To use DHCP or not depends on your buisness and it's needs and culture.

 

[nwboson]

Kid: "We have no problems with keeping unqualified people of(f) our machine networks because we have lots of cameras and we don't mind firing people.
To use DHCP or not depends on your bu(si)ness and it's needs and culture."

Gosh, having Igor the Hatchet Man to whack employees sounds wonderful. In lieu of the delightful atmosphere described by Mr. Kid, and as an OEM integrator faced with any number of potential customers that I'd prefer to keep off the industrial network, I will still posit that setting up DHCP on an industrial network is usually an insecure thing to do.

However, if you are plugging ports and setting up for known MACs, that is a great approach - another example of the value of our differing experiences here on plcs.net

 

[The Plc Kid]

At a different employer they wanted to find a way to disable the dvd drives on all the hmi panel pc units because people were opening the cabinets and playing movies on them and this was their worry. I would be more worried about keeping them out of the panel period because dvd drives and dhcp are things that can cause problems but there are hundered of other things in most control cabinets that can cause just as much harm to equipment or the person.

I don't share the view of locking down everything in the cabinet but just keep people out of it that are not supposed to be in it to keep from damaging themsleves or equipment.

As far as the atmosphere it is one of the best companys in the metro atlanta area but we have rules about panels and such that are clearly explained to you and if you break them then you are gone. The rules are their for employee safety and only 1 person had to fired to make a example. We have had zero unauthorized people in the panels since.

 

[The Plc Kid]

@realolman

To make this a little easier to understand think of it like this. We both have a land line phone and if you pickup a handset you know you are connected to the phone network because you hear a dial tone. you can' call me though if you don't know my number correct but if you do know my number you can call me and we can talk.

Now to further add if you call me onmy number and you are speaking spanish and I am speaking english then we are on the same network and we are both taling but we are not communicating because I don't understand spanish.I this situation we are talking but we are not using the same protocol which in this case would be english and spanish and in the plc world would be Ethernet IP in your case. When your coworker tells you that I don't understand spanich and you start speaking english then we are both on the same protocol and we are communicating with each other.

 

[The Plc Kid]

@nwboson

If I were building OEM equipment like you are then no I would not use DHCP if the end customer did not spec or ask for it. Based on previous threads I think realolman to be in a plant manufacturing enviroment in maintenance or E&I or something related and in that enviroment dhcp is a lifesaver.

I have a plant with over 800 plc's and growing so if I had to pull prints to get a static address or open the cabinet and suit up to read the enbt or manage a spreadsheet for that many units it would be a real pain. I know because I have done it both ways.As I said earlier it dependes on your buisness OEM,manufaturiung plant, etc and your culture.