IP Addresses / Ethernet Network

SamHefner

Member
Join Date
May 2009
Location
Jackson
Posts
2
Hi, I'm developing software for AB Compactlogix/Panelview application. System Comm. is ethernet. I configured ethernet network yesterday assigning new IP address to laptop computer with similar addresses for the devices on the logix network. But back at the office today, of course, same ethernet port now fails to connect to office network router/internet service. Unknown to me, the laptop was reset back to previous settings, thus resetting the IP address. and now it works on the network and internet service. But I'll have to reconfigure the IP address to reconnect to Logix network. Any suggestions as the best way to keep switching IP addresses?
 
Short answer: DHCP or lack thereof.

Somewhat longer answer: Your office uses a DHCP service, most likely running on your router. No such service exists on the Logix network, so you needed to manually assign IP addressing. You may consider assigning the Logix network within the autoconfiguration block, 169.254.0.0/16. When you connect your laptop, DHCP will fail and revert to this IP block, which would allow connectivity to devices manually configured in this range.
 
When the automation system and the office network are not connected, I like to set up the "Alternate Configuration" for my Ethernet adapter's TCP/IP setting for an IP address in the range of the automation system.

When I plug in at the office, DHCP works and I get an office address.

When I plug in at the automation system, DHCP times out and the system gets the Alternate Configuration address. If I had not set up the Alternate Configuration address, the PC would have an "automatic private IP".

There are scripts, batch files, and programs that do this more effectively, but I just use good old TCP/IP Alternate Configuration.
 
This is what my IT guys insist on.

When I connect to the company network, I use the built in ethernet port on my notebook. I leave this config alone.

When I connect to any other network, I use a USB ethernet adapter. I have complete control over IP etc.

So all I have to do is plug in the right port. USB ethernet adapter is $10-15.
 
You may consider assigning the Logix network within the autoconfiguration block, 169.254.0.0/16. When you connect your laptop, DHCP will fail and revert to this IP block, which would allow connectivity to devices manually configured in this range.[/quote]

Could you expand on this? Do you mean if your laptop is setup to use DHCP and it fails that it will revert to this ip range?

Is this OS specific? Where can I find more info on this?

I have been doing a lot of reading on Ethernet networking try to teach myself networking as a whole but I have never seen this before. Looks very interesting
 

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