1756-EWEB no response to ping

[drums4lyf]

I've got a 1756-EWEB module where I am trying to do some sockets communication where I'm receiving messages from a remote client over TCP/IP. I've used this same method on a CompactLogix PLC with built-in Ethernet/IP without issue. The problem is not so much with the sockets interface, rather, it is that I can't seem to reach the EWEB module without physically connecting to the same switch as the EWEB.

There is a 1756-ENBT/A in the same rack as the 1756-EWEB, and I can ping the ENBT and view it's webpage from anywhere, but I cannot even ping the EWEB module. Both units are physically connected to the same local unmanaged switch in the control cabinet. I can reach both when I'm plugged into that same switch, but if I go to a PC connected elsewhere in the plant through a managed switch on our plant network, I can ping the ENBT but not the EWEB.

I should note that the ENBT, EWEB, and PC from which I'm trying to ping are all on the same subnet as well. There is physically one connection to the house network that goes to the switch in the control cabinet, and again, I can ping the ENBT through that connection, but not the EWEB.

Any help is greatly appreciated...haven't been this stumped in a long time.

 

[drums4lyf]

If it helps, here is the IP info for everything:
ENBT: IP=172.22.0.201, subnet mask=255.255.255, gateway=172.22.0.249
EWEB: IP=172.22.0.202, subnet mask=255.255.255, gateway=172.22.0.249
PC: IP=172.22.0.126, subnet mask=255.255.255, gateway=172.22.0.249

 

[drums4lyf]

Port security

Ok, I may have solved this, just wanted to post the potential solution in case others run into this issue. Our IT department has implemented port security on all of the managed switches, which limits the number of MAC addresses (3 in our case) that can connect through one port on the switch. Since my control cabinet has several unmanaged switches that mostly handle traffic internal to the machine, and there is only one connection to the managed/plant switch, I found I actually can't ping most of the devices connected to the unmanaged switches in the cabinet. When I connect directly to the unmanaged switches in in the cabinet, I can ping everything in there. Since I'm not changing subnets by moving where I'm connected, I think it's a pretty good indicator that port security is the problem, so we will try to get the MAC address limit on that port increased.

 

[Geospark]

I've got a 1756-EWEB module where I am trying to do some sockets communication where I'm receiving messages from a remote client over TCP/IP...

...OK, Industrial Networking...

...I go to a PC connected elsewhere in the plant through a managed switch on our plant network, I can ping the ENBT but not the EWEB...

...Plant Network...Yep, Industrial Networking...

...Our IT department has implemented port security on all of the managed switches...

...Oh dear...my diagnosis is not good. It would appear as though a virus, of the worst kind, has "taken over" your Industrial Network...

...Ok, I may have solved this...we will "try" to get the MAC address limit on that port increased...

..."try"?, on "yere" Industrial Network?...

...I would concentrate on eradicating the cause here rather than curing the symptoms...

With respect to you, and your I.T. Department, and all joking aside, and without knowing your industry, and required levels of security, I would, wherever possible, not let Enterprise I.T. experts administrate over Industrial Networks.

Their philosophy, training, goals and priorities are usually of a far distant realm to ours.

Besides, everyone knows that good Port Security is all about keeping the liquor cabinet locked.

I do hope you resolve this though and apologies for the rant.

Regards,
George