HELP: getting error "13:01:48 CDT: %IP-4-DUPADDR: Duplicate address x.x.54.49 on Vlan54, sourced by f866.f2b4.bf3f"

[dtipps]

Hello! (a little about me before we get started. I lost my network engineer and I've been tasked with taking his place. I know close to nothing about networking, though I'm slowly learning. Please imagine we are on reddit and we're on the ELI5 sub)

I just found this error while going through the log of one of my routers. I'm gone as far as I know how to go. Here's what I did:

1. I ran show mac address-table | inc bf3f and traced that path through like 4 switches (using show cdp neighbor) until I got a switch that would show " 84b2.6161.bf3f    static ip,ipx,assigned,other Switch" but no port!

If I do a "show run" then I see that "Interface VLAN 54's ip is set to the exact same IP "x.x.54.49" that's in the error message. 

I'm not sure what to do after this. I notice some vlans have IPs associated with them, others don't. I don't know why? I am only getting the 1 mac address so I can't hunt down the "conflicting device."

I do know that on two different routers the vlan is configured the same, but so are the other vlans, so I don't think that's the problem?

I'm at a loss. Please help.

[Georg Pauwen]

Hello,

-->I do know that on two different routers the vlan is configured the same, but so are the other vlans <--

That sounds like an HSRP setup. Basically, the VLAN interfaces only need to be configured on the device(s) that do(es) the inter-Vlan routing. Can you post the config of both routers ?

[dtipps]

Oh, that makes sense. yeah, both routers do that (for different sections of the campus).

I'll check with my supervisor to see if he's cool with me posting the whole (or part) of the config.

thanks for the help!