CompactLogix communictation problem

Kayser

Member
Join Date
Jul 2011
Location
Missouri
Posts
9
I am new to using AB controls, I have a CompactLogix L23E and Im finishing a project someone else started, I had to change the IP address and the subnet mask, I went online and change the address on in the port configuration tab and pressed apply, Now I can ping the PLC but I cannot connect, or even see the processor in the RSLinx, the MS light keeps flashing red and the NS light stays red

Please help
 
That's probably an IP Address Conflict with something else on the network.

After you PING the module, type "ARP -A" and check the ARP table to be sure the MAC ID you have in the ARP table really matches the CompactLogix. Rockwell MAC ID's start with "00 00 BC" and the actual MAC of the controller Ethernet port should be on a sticker somewhere.


Do you have access to the serial port and an ordinary "null-modem" serial cable ? It's a straightforward operation to connection serially and use the RSLinx browse to access the Ethernet module configuration over the CompactLogix backplane.
 
reply

will any null modem cable work or do have to use one of AB's cables, and if its and IP problem would the MS flash red and the NS light stay red when its just connect to a switch and im not trying to communicate with it
 
Any null modem cable will work. The default Channel 0 serial port communication parameters for any ControlLogix-family controller are DF1 Full Duplex, 19200 baud, 8/N/1 framing, CRC error checking.

In the case of an IP conflict, the user manual I'm looking at (ENET-UM001) says MS will be steady red and NS will flash red.

You posted the opposite, so either you posted incorrectly or something very strange is going on.

Some "switches" actually have a management feature in them so they use an IP address, so maybe the controller is conflicting with the switch itself.

What exactly are the IP Address, Subnet Mask, and Default Gateway values you set in the controller ?
 
the IP address is 10.96.82.30
Subnet is 255.255.255.0
and gateway is 10.86.81.0

and yeah I think something wierd is going on, is there away to reset the controler back to factory defaults
 
The controller might be objecting to the IP address and the Default Gateway not being on the same subnet.

IP Address: 10.96.82.30
Subnet 255.255.255.0
Gateway 10.96.81.1

The Subnet Mask being set to "255.255.255.0" is also called a "/24" mask, indicating the first 24 bits (three bytes) of the IP address must be the same for any two devices to talk to one another.

Because the Gateway is actually on a different Subnet, the controller couldn't talk to the Gateway.

Simple fix: set the Subnet Mask so it will allow both the IP Address and the Default Gateway to be on the same Subnet:

IP Address: 10.96.82.30
Subnet 255.255.252.0
Gateway 10.96.81.1
 
In ControlLogix, the Ethernet modules retain their configuration in a separate Nonvolatile memory from the rest of the system, so there is no way to disconnect the battery and drain the RAM like there is for the User program.

The serial port method is your best bet right now.

Update: I tested this with a ControlLogix 1756-ENBT. When I clicked "Apply" in the RSLinx Module Configuration applet the software gave me an "Unknown Communication Error 0x09" message, but the configuration with mis-matched subnets for the IP Address and the Default Gateway appeared to have been applied to the module.

But when I cycled power to the module, the 1756-ENBT booted, passed the self-test, then went into a fault mode in which the NET LED was solid red and the OK LED was flashing red. The module scrolled across the display that it is in BOOTP mode and that there is an invalid network configuration.

I know that IP address settings don't fully take effect until the module is reset, so it makes sense that it happened after a power cycle.

Because the 1756-ENBT worked this way, it is likely that your packaged CompactLogix is also in BOOTP mode. Run the RA BOOTP/DHCP Utility and look for broadcasts from the CompactLogix.
 
Last edited:
You were right the gateway was bad, Don't always rely on your IT dept to give the correct info, I used the BOOTP utility and was able to change the settings,

Thanks for the help
 

Similar Topics

Hello all, and thank you in advance for any assistance you may be able to provide! This is my first post, so if I need to reformat or change...
Replies
0
Views
22
We are trying to poll data coming from a PLC for remote monitoring we have the IP address of the PLC and the default port number and the path is...
Replies
25
Views
418
Hi everyone, this is my first time trying to setup encoder counts and track the traveled distance and speed i am using L27ERM QBFC1B processor...
Replies
12
Views
332
I have a device that is currently connected to a UR 10 robot through a UR Cap and I would like to connect the device to an Allen Bradley...
Replies
3
Views
316
I have a device that is currently connected to a UR 10 robot through a UR Cap and I would like to connect the device to an Allen Bradley...
Replies
0
Views
102
Back
Top Bottom