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New Member


Hi All, hope someone can help

Scenario 1: 

WLC:                WLC4402 software version

APs:                 1242AG converted to LAP IOS version 12.4(16b)JA.

Around 24 APs, all in the same VLAN 10:

Wifi Clients:      Industrial PLCs using “Industrial Protocol: Ethernet/IP, ENIP” such as Rockwell or Allen Bradley.

                        VLAN 20, subnet

LAN devices:     A couple of master wired PLCs that controls all the WiFi industrial clients.

                        VLAN 20

Application:       A PC in the LAN (wired) use Rockwell RSLINX software to discover and check wifi clients by BROADCASTING the subnet

                        VLAN 20. The discovery broadcasting is done every minute.

Result:             Result is ok. It discovers all the WiFi clients

Notice that all the System (Wifi clients, Master PLC on the LAN, and monitoring PC in the LAN), all of them belong to the same VLAN 20, This VLAN has wireless and wired clients, the wired segment are Master PLCs and the monitoring PC.

The APs use a different VLAN, and the WLC Management interface use a different one too)

Broadcast Forwarding is enabled. Multicast mode is Unicast.

Scenario 2:

After upgrading the WLC to software version and the APs to IOS version 12.4(23c)JA2. the RSLINX application find some WiFi clients, but not others. It is random. Suddenly a client stops appearing, and suddenly appears again. There have not been any configuration changes in the WLC prior or after the software upgrade.

After capturing the traffic going out the monitoring PC, I can see the broadcast discovery query, however only some of them respond each time (and they keep changing after each discovery broadcasting query)

Can you help?

Thanks in advance.

Alex Bertrán

Hall of Fame Super Silver


That is a big jump in code, but its better than sticking with v5:)  There are changes that could of been removed during the upgrade sue to the fact that it the feature has been removed with the newer code, etc.  What I would try is to enable passive clients on the wlan ssid advanced tab.  If that doesn't help, many times enabling global multicast (Controller | Multicast).

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New Member


Hi Scott, many thanks for your anwer.

Yes it is a big jump, but I followed the necessary steps from v5 to v5.2 and then to v7...if I remember well as explained in the Cisco documentation for upgrading procedure.

I also escalated the case to Cisco TAC and they made some questions that I have already answered... see below please, I explain further details regarding the WiFi clients.

Besides this, I cannot find that option to enable "passive clients" in the Advanced TAB for the SSID...maybe in the CLI instead of the GUI?? Thanks again!!

•2)           Also we need to know if those wireless clients using static IP or DHCP?
•a.                   They use static IPs
•3)           Are they passive clients?
•a.                   Kind of… let me explain it. The clients are AGVs (automatic guide vehicles). 
From a network perspective every WiFi client is a Hirschmann device (Belden brand), configured with a static IP
into the subnet, which it has a single wired client behind with another static IP in the same
range (plus Mask and GW). This wired, and for wired I mean wired to the WiFi Hirschmann client, is a
PLC (programmable logic controller). At the WLC you can see the MAC address of the Hirschmann
device associated to the IP of the PLC. The Hirschmann is performing a kind of “NAT” for the MACs it
has behind. The PLCs mounted on every AGV and wired to a Hirschmann WiFi client are the devices
that the RSLINX monitors. At the end, the Hirschmann WiFi client is no acting exactly as a WGB.
•b.                   Those MAC addresses you can see in the next screenshot (WLC client list) are the Hirschmann’s 
MAC addresses. However the IP showed is the PLC’s IP address

Hall of Fame Super Silver


The passive client is in the WLAN SSID advanced tab in the right hand side. It's a checkbox.


Scott Fella

Sent from my iPhone

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New Member


mmm ...I read that option is not available on WLC 4402, it appears just on the 5500 and the 2100 WLCs...

Maybe adding MACs into the Security MAC Filtering...

Anyway, thanks a lot for your comments

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