Introduced Catalyst 3650 into campus with Catalyst 3750s: getting duplicate IP address problems

[Richard Bradfield]

During the New year break we introduced a Catalyst 3650 into one of our factory networks, so it can provide full power to the 2702 APs being installed in the production area. All the rest of the switches are 3750 s. Since the install  some of the PLCs come up intermittently with a duplicate IP address message and the Ethernet interface goes to sleep. These are not connected to the 3650. and the VLAN they are on does not go to the 3650. There is nothing in the ARP table indicating any duplicate addresses and the spanning tree is stable.

So my question is does the 3650 work differently to the 3750 at Layer 2 level?

when I remove the 3650 all works ok

I notice that when the 3650 is ON when I show the ARP for the PLC the age is always 0 till it fails.

when the 3650 is OFF the network I see the age incrementing in the  ARP TABLE 

[billjarrett]

Did you ever resolve this issue? We started seeing this after introducing a 3650 also.

[Richard Bradfield]

Yes,

Had to put the

nmsp attachment suppress

command on all interfaces

[billjarrett]

For anyone that comes across this post first like I did, after more digging I found this. It's the answer we are going to move forward with.. If I don't return here, it worked.

http://networkengineering.stackexchange.com/questions/6617/cisco-3560x-switch-mac-reported-with-same-ip-as-other-equipment