ethernet comms between different networks?

[dunc 8]

i wish to segment my ip address areas out to free up more available IP addresses and to give some area definition based on the numbers used. i want to keep things simple without messing with dhcp or managed switches as we have limited management resource and a mixture of old and new equipment, some of which wont support dhcp anyway.

 

i have a network setup via 3 q03ude cpus.

i have had no issues so far until i come to the 3 PLCs communicating over a tcp/ip connection via an open port connection on the master plc.

2 of the plcs have the ip address 192.168.3.x but one has the ip address of 192.168.11.x

 

they will communicate fine if on the same network with the last set of ip address numbers being the unique identifier, just not if i use the last 2 sets of numbers as the unique identifiers, even with a blank subnet mask in the PLC ethernet setting tab (no subnet masking?)

with a subnet mask of 255.255.0.0 my pc will pickup all the devices on the various ip address ranges as long as the first 2 numbers are 19.168.x.x which is as expected.

 

how do i go about getting the tcp/ip comms to work as i want to? the only settings i can adjust on the function block are the ip address itself (in hex) and the port numbers. this is only at the master PLC end. only port numbers can be changed at the slave PLCs.

any assistance would be appreciated. i have limited networking knowledge. thanks

 

[WattUp 34]

Assuming your entire network is 192.168.*.* based, if you are on a 10.25** network that might be an issue. 

I believe you would setup each PLC to be network 1, station 1,2, and 3. Then use [Station No <-> IP address] to point the stations to the other IP 

 

then using your  GP.READ you setup which station you are reading from. 

[dunc 8]

yes, everything is 192.168.x.x based.

i am not using the gp.read instruction. the system is setup using a function block downloaded from mitsubishi that sets the ip address and the port information only. i am hoping it is something i need to fill in on the network parameter pages, just struggling due to my limited knowledge.

having done some extra reading i have a few extra things i can try, only problem is i only get the plant on a friday evening as it is running the rest of the time. will report back on how i get on

 

[WattUp 34]

I have never used the function block method, but I would bet the Station number still matters, so verify the network numbers match and station number should be unique for each PLC. 

 

"Only get the plant friday night"  -- this sounds all too familiar hahahaha 

if you have some extra PLCs laying around I highly recommend setting up a test bench, that was the only way i got the communication worked out. 

[dunc 8]

i wish, i am in a maintenance department. we barely have enough to keep things going, let alone spares to set up a test rig. 

everything i do has to be on the live system!!!

i have no station number issues when i put them all on the same network, so wouldnt have thought it would be that? did get a chance to get on it last friday as had issues with something else :(

 

will try again this friday!

[WattUp 34]

you do have the subnet set to 255.255.0.0 in all PLCs right?  You mention a test leaving it blank, but i think that would actually default it to 255.255.255.0