1769-L35E Ethernet problem

JasonWade

Member
Join Date
Oct 2005
Location
Preston
Posts
160
Hi,

I'm unable to find this PLC using RSLinx 2.51.

I have configured my pc LAN port to be 192.168.1.20, connected the PLC to PC by a straight thru ethernet cable via a switch, found the plc (I think?) using BOOTP-DHCP Server and changed its IP address to a 192.168.5.5, BOOTP-DHCP then reports a connection to the device with this address, when I try to DISABLE BOOTP/DHCP I get a timeout error.

So I guess this means the PLC has the new IP address but will lose it when the power goes off?

So while the power remains on I hve tried pinging the new address and it looks ok.

I then tried both drivers in Linx (Ethernet Devices & Ethernet/IP Driver) but still cannot find the PLC. Using 'Ethernet Devices' I can see a device called 'Ethernet Gateway' (I think this is correct, I don't have the PLC right now), but cannot find the PLC.

I have no yellow question marks, I have the ESD files loaded, I have read the other posts about CompactLogix/Ethernet.

One niggle I have is that BOOTP-DHCP Server finds a device (I assumed to be the PLC) with a MAC address that is different from the MAC address printed on the chips inside the CPU. (I only have the PC, switch and PLC connected).

Can anyone suggest where I am going wrong?
 
I suggest keeping the PC and PLC ethernet IP addresses on the same subnet.

>...192.168.1.20... ...192.168.5.5

BootP will show MAC ids for all devices it sees. I usually disable the wireless on my notebook when I use BootP to eliminate the MAC id clutter. Make sure only a single MAC id is listed to insure you assign the IP address to the intended device.

Addresses on different subnets also require the subnet mask to be set correctly. If creating/changing the PC IP is a problem, windows will allow alternate IPs. I currently have 5 alternate IPs on my notebook and have no problems with BootP or Linx.

I have had limited success using BootP to set a static IP with no known reason why sometimes it works and other times not. I use BootP to establish an IP and then navigate to the device using Linx and right-click properties to make the IP static.
I also suggest using the Ethernet/IP driver but you will need to add the assigned device IP to the driver's IP address list.


>So I guess this means the PLC has the new IP address but will
>lose it when the power goes off?

Most likely.

>One niggle I have is that BOOTP-DHCP Server finds a device (I
>assumed to be the PLC) with a MAC address that is different from
>the MAC address printed on the chips inside the CPU. (I only
>have the PC, switch and PLC connected).

The device MAC id should be on a label on the side or rear of the module. And of course it should be one of the entries in the BootP list.
 
Along the lines with what tkemmann suggested, keep the addresses similar. If you need the PLC to be 192.168.5.5, then make your PC 192.168.5.6 (or something like that). This is the simpilist setup and you can rule out any other problems (cabling, switch and such). Once you know it works, then you can mess around with different subnet masks if you have to.

One thing that I have noticed about BootP is that sometimes the MAC ID will shot up on the relations table, but sometimes it takes a bit of time before the requests that you send to the device will make it successfully.

Also, do you have a CP3 cable? You could connect via the serial port and get everthing setup.
 
tkemmann....
I also suggest using the Ethernet/IP driver but you will need to add the assigned device IP to the driver's IP address list.

Incorrect - The /IP driver is the one that browses the selected subnet to find devices, you do not add IP addresses to it. The "Ethernet Devices" driver is the one where you have to add the specific IPs of the PLCs and Comms cards.

ghettofreeryder....
I presume you have the ETH-IP driver set for remote subnet with 192.168.5.1 and 255.255.255.0?

If the subnet mask were set to 255.255.255.0, then the first three octets of the two IP adresses have to mask exactly. In Jason's case, using 192.168.5.5 and 192.168.1.20 would not work with the 255.255.255.0 mask.

Jason - keep it simple, keep your comms within the same subnet, makes life a whole lot easier.

Say you want your PLC to be 192.168.5.5, then do as dmroeder suggests and set your PC to 192.168.5.xx, where xx can be any number 1-254 - use a subnet mask of 255.255.255.0, meaning only the last octet of the IP address is the ethernet node number.

When you first start Bootp, it will ask for network settings, just put the subnet mask to 255.255.255.0, you may need to reset it to that.
 

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