Ethernet Comms Confusion

krakenfan69 · Apr 12, 2013

I set up a CompactLogix PLC with a PV+600 (why they didnt get alarger dislay i will never understand) through a 5 port hub. comms are great and the pv sees the plc. if i then remove the hub and plug the PLC directy into the PV it con bo loger see the PLC. Add the hub back in and its good again. What gives? Clearly there is a piece to this setup I am failing to understand.

Kraken Fan #69

alan_505 · Apr 12, 2013

When you connect directly are you using a crossover cable?

Ranjith · Apr 12, 2013

You probably need a x over cable to connect it direct. Not straight trough.

krakenfan69 · Apr 12, 2013

You know I'm not sure. It was in place when I got there and i didn't think to check. I did use that same cable to connect the PV to the hub however. It was not working when I arrived however as I was sent to dump in someone else's program and do loop checks. I'll check it in the morning. Thanks for the heads up guys.

Kraken Fan #69

nightline · Apr 12, 2013

Most hub's and switches are auto-crossing today.
So with a hub or switch with auto-crossing in the communication line, it makes no sense if you use Cross-cable or straight...

If you remove the switch or hub for a direct connection like you did, it makes sense like mentioned in the posts before.

Jack

krakenfan69 · Apr 13, 2013

When I got to site this morning I used a crossover adapter (Yeah, I didn't have a crossover cable but this thing I have. lol ) and it worked just fine. Plans now are to add a 24 industrail hub to make it eaiser to be online and still have PV comms.

Thanks again for all the help!

Kraken Fan #69

alan_505 · Apr 13, 2013

If you are going to put a hub in, make sure that somewhere in the panel you list all the IP addresses connected to it so that when the next person comes along they can pick an address that is not used, and not have to guess and possibly pick a duplicate address.

i wish all machine manufacturers and sites did this, as it would make connecting to there network so much easier.

Alan

krakenfan69 · Apr 13, 2013

Yeah we always put Dymo labels on the PLC and the HMI for easy reference. I also leave an Excel file with a list of all device IP addresses on location (or other locations if they are connected via radio) so we can keep track and make additions simpler.

Kraken Fan #69

nightline · Apr 13, 2013

I hope you mean that you will install a switch instead of a hub...

Jack

MerryChrisSmith · Apr 13, 2013

I wish that something on an industrial network had a built in DHCP server so I could get assigned an unused address automatically.

Also, which CompactLogix are you using? If it's the old style(L23, L32, L35, L43, L45) then yes you most likely need a crossover cable. However, I wouldn't think you'd need a crossover cable on the newer 5370 CompactLogix controllers. I thought the built-in redundant Ethernet ports acted like a switch. There is the ability to disable one of these ports, although if you got the PLC new that's probably not the case.

krakenfan69 · Apr 13, 2013

The platform is a Compact Logix 1769-L32E. I have always ignorantly used the terms switch and hub interchangeably. 7-UP or Sprite anyone? After a quick google search on the difference in Hubs and Switches it will indeed be a switch. Although I don't claim to even yet fully grasp the diff. To me it sounds like the white zip tie vs black zip tie conundrum. Why would I ever use a white zip tie? Always use black (or a Switch )and only have to stock one type. (Yes I know they are a bit cheaper but really?) When would I ever choose to install a simple Hub?

Thanks again for all the help and by all means if someone would like to expand on the Switch vs Hub then please enlighten me further. Is everything on this site searchable or is there a way to add tags to different threads for later searches?

http://catalog.weidmueller.com/catalog/Start.do?localeId=en&ObjectID=8896940000

Kraken Fan #69

daba · Apr 14, 2013

MerryChrisSmith said:
I wish that something on an industrial network had a built in DHCP server so I could get assigned an unused address automatically.

I wouldn't have a DHCP server assigning IP addresses to my control network devices.....

I presume you are talking about getting a "compatible" IP address for your laptop when you connect it to the switch?

The Plc Kid · Apr 14, 2013

daba said:
I wouldn't have a DHCP server assigning IP addresses to my control network devices.....

Nothing wrong with it if done the right way. I sue DHCP persistence ( per port )with logix auto device config and it works well.

I have about 70 nodes on one line setup like that. You can also do DHCP per port for you programming port like a graceport or similar product where you would plug your laptop in.

daba · Apr 14, 2013

The Plc Kid said:
Nothing wrong with it if done the right way. I sue DHCP persistence ( per port )with logix auto device config and it works well.

DHCP persistence - Not quite the same as vanilla DHCP, which just gives a spare address to the first device that asks for one. And gotta be a PITA if the switch fails.

I prefer, and recommend, to fix IP addresses on automation nets.

Each to their own....

MerryChrisSmith · Apr 15, 2013

daba said:
I wouldn't have a DHCP server assigning IP addresses to my control network devices.....

I presume you are talking about getting a "compatible" IP address for your laptop when you connect it to the switch?

Yes, I am talking about programming computers only. I do like the idea of DHCP per port as mentioned above however.

Ethernet Comms Confusion

krakenfan69

Lifetime Supporting Member

alan_505

Lifetime Supporting Member

Ranjith

Member

krakenfan69

Lifetime Supporting Member

nightline

Member

krakenfan69

Lifetime Supporting Member

alan_505

Lifetime Supporting Member

krakenfan69

Lifetime Supporting Member

nightline

Member

MerryChrisSmith

Member

krakenfan69

Lifetime Supporting Member

daba

Lifetime Supporting Member

The Plc Kid

Member

daba

Lifetime Supporting Member

MerryChrisSmith

Member

Similar Topics