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Figure An Ip Address


Bozz45
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Hi, I have computer hooked up to a router and then to an industrial PLC. Nothing else on the network.

My computer has an static IP of 192.168.0.11 subnet 255.255.255.0

The problem I have is I don't know what the IP of the industrial PLC is and I can't change it until can connect to it.

I have tried to use Nmap to scan for it, and it is not within the range of 192.168.0.1 to 192.168.0.254.

When I try to use nmap 192.168.0.1/0 or / 8 or /16 as soon as it gets to 192.168.1.1 I get an error and it can't find anything else.

I am wondering if I have to change my subnet. (I am newbie with Nmap.)

The guy before me could have set the PLC's IP address to anything.

my computer shows an "network" as soon as I plug the cable into the PLC,

Is there another way to find the PLC's current IP address?

thanks

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Can you give us more info on the PLC? What is the PLC, what does it do. if it sits on the other side of the router, like a modem, you can't reach it on the same subnet as your routers inner lan interface. If it is a modem, try pinging or connectiong to 192.168.100.1. Thats what most of them function on by default and usually have no way to change it.

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If you still have trouble and you have any access to the router then you might be able to get it to tell you what networks it thinks are connected to each interface. That would hopefully give you a set of network ranges to start searching with nmap.

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Can you give us more info on the PLC? What is the PLC, what does it do. if it sits on the other side of the router, like a modem, you can't reach it on the same subnet as your routers inner lan interface. If it is a modem, try pinging or connectiong to 192.168.100.1. Thats what most of them function on by default and usually have no way to change it.

it's a Omron Safety PLC, and the module I am trying to connect to is the EIP module. (Ethernet I/P). Normally comes with a default IP address of 192.168.250.1, but once you change it, you have to have the current IP to change it again. and I made a mistake in saying router, it's a Cisco Catalyst 2960 8 port SWITCH.

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it's a Omron Safety PLC, and the module I am trying to connect to is the EIP module. (Ethernet I/P). Normally comes with a default IP address of 192.168.250.1, but once you change it, you have to have the current IP to change it again. and I made a mistake in saying router, it's a Cisco Catalyst 2960 8 port SWITCH.

Log on to the switch, and you should be able to show the connections at each interface with "show interfaces" or "show mac-address-table". Switches only work at layer 2, so not sure if you will be able to get the IP directly from the switch, but might be able to get the mac address and somehow find it from that with an arping against the mac address from the workstation, and then look up the local arp table on the workstation.

example: "show mac-address-table" and document all known mac addresses, then from the workstation, arping each mac address, which will ping each device, then from the workstation do an "arp -a" to display your local arp table, and hopefully, the matching mac address will show up with the associated IP address.

Edited by digip
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