How To Determine IP Address of AB PLC

[Philadelphia Frank]

When I connect my laptop to a Compactlogix PLC through the ethernet port, I need to set up the IP address of my laptop so the first three octets match those of the PLC. If the PLC is 170.10.50.100, my laptop must be 170.10.50.xxx.

What do I do if I need to connect to a PLC with an unknown IP address? I know there is a DOS command "ping" that can be used to verify a connection between the laptop and PLC, is there a DOS command that will show what devices are on a network?

Is there a way to set up my laptop so RSWho will show devices on the network even if the first three octets don't match?

Thank you for your time and help;
Frank

 

[LJBMatt]

The easiest way is to find the IP address is to connect using a serial cable and the DF1 driver in RSLinx to connect to the processor and go to the properties of the Ethernet port. There it will list the current IP address and allow you to make changes as well.

 

[rdrast]

Use a serial connection to the PLC, and read it's IP.
And the 'first three octets matching' has nothing to do with connecting. You need to be on the same subnet, no matter how many octets that requires.

 

[OZEE]

That's one thing that I really like about the 1756-ENBT -- It tells you the IP address on the front panel.

 

[TimWilborne]

Disclaimer - Advertising a product I sell

This is exactly what the IP Explorer was designed for. It will read the IP Address
http://www.twcontrols.com/index.php?option=com_content&task=view&id=112&Itemid=76

 

[Ron Beaufort]

you should take a look at this gadget ...

http://forums.mrplc.com/index.php?s=&showtopic=11669&view=findpost&p=56290

it comes in handy when (for one reason or another) you can NOT connect to the serial port by DF1 ...

TWControls sent me an updated sample to try out in the lab ... it works fine on everything that I've tried it out on ...

PS Edit ... looks like TW and I almost posted right on top of each other ... the picture in his link is the model that I've tried ...

 

[tragically1969]

If you can restart the PLC then download Wireshark, set up a capture and reboot the PLC, it should broadcast its IP address as an ARP packet which you can then look at using the log viewer in Wireshark

We use it when gear arrives back from site that we dont know the IP address of, it works well.

 

[jimbo3123]

If you can restart the PLC then download Wireshark, set up a capture and reboot the PLC, it should broadcast its IP address as an ARP packet which you can then look at using the log viewer in Wireshark

We use it when gear arrives back from site that we dont know the IP address of, it works well.

You can get the same info from the Rockwell BootP Server, no need to download wireshark. You still need to restart the PLC though.

 

[Ken Roach]

A slight correction:

The BOOTP/DHCP request is only sent on restart of the controller if the Ethernet interface is configured to use BOOTP or DHCP. If the controller is set to a static IP address, nothing is sent except the ARP broadcast.

Wireshark (or any other ethernet analyzer) is an almost foolproof method for determining unknown IP addresses on embedded devices. The IP explorer uses the same principles and doesn't require that you download freeware or learn the internals of your adapters and firewalls.

I can usually connect using RSLinx and another method, but for devices like the 1794-AENT/A or PLC-5E that have no display and may have their other ports configured for a different application, the ARP method works well.

 

[TimWilborne]

The IP explorer uses the same principles and doesn't require that you download freeware or learn the internals of your adapters and firewalls.

The IP Explorer actually has a few additional features beyond that to help discover the IP Address. It is especially helpful in those devices that don't do an ARP broadcast on power up. I believe an example would be the 1761-NET-ENI but I don't have one handy to test on

 

[monkeyhead]

There is also a program called nmap that can be used to do a 'host discovery' scan on a chunk of the network. This won't tell you the exact address of the PLC, but it will let you know what addresses are online and in use so you can narrow your search.

Or you could scan a known PLC's (of the same type) IP address with nmap and use it's open port list as a 'fingerprint' to use to scan the other online hosts with. If you find another host with the same open port configuration, then you probably have your unkown PLC's address.

Nmap is a very powerful network analysis tool, but if you don't know the basics of TCP/IP it might seem a little overwhelming.

The serial port and wireshark suggestions are probably the easiest suggestions.

 

[hussein kamal]

hi every one
I'm so sorry to ask my question is i have two touch screen and both of them can't find the ip address so how to find sw to connect to this screen and get ip address to upload program from it or how find commend in dos to get ip address

 

[bornwild]

Forget everything just use wire shark as someone suggested above. It is very easy to get not only ip address but also the mac address. If you need.

 

[hussein kamal]

thanks to you for ans
and i found commend
on windows...
Go Start menu... Run
Type in "cmd" and hit enter
Type "ipconfig" and hit enter
will show the ip address
but not try on plc's or touch screen
at all thanks for your replay

 

[bornwild]

thanks to you for ans
and i found commend
on windows...
Go Start menu... Run
Type in "cmd" and hit enter
Type "ipconfig" and hit enter
will show the ip address
but not try on plc's or touch screen
at all thanks for your replay

Hussein, That is going to show the ip adresss of your network card . It will not show you the ip of the plc or touch screen