%IP-4-DUPADDR: Duplicate address 192.168.100.22 on Vlan100, sourced by xxxx.xxxx.xxxx

[fotismark]

Hello,

Maybe someone can explain to me this behavior?

%IP-4-DUPADDR: Duplicate address 192.168.100.22 on Vlan100, sourced by 80e8.6fad.67a7

SW-ATH-FL2-1#sh mac-address-table | i 67a7
   1    80e8.6fad.67a7    DYNAMIC     Po2
 100    80e8.6fad.67a7    DYNAMIC     Po2

It learnes the same MAC address from 2 different VLANS? There are only 2 interfaces on VLAN 1 and those are not used and shut down.

Po2 is going to another switch on another floor which there there is no duplication with this Mac Address but with different, on its Po1 which leads to basement.

Not my design of this network, but I am trying to understand that behavior.

Thanks

[Mark Malone · Accepted solution]

Hi
someone has most likely given the same ip maybe static to another end device , trace the mac address to each port check the end device , happens when dhcp gives out one address then a user assigns himself the same address somewhere else , switch sees 2 macs resolving to same ip address coming from different vlans locations, first thing to do is check the end devices these macs are associated to , follow the mac address from where its being learned
sh mac address-table address 80e8.6fad.67a7

[fotismark]

Thank you, I will although it is kinda hard because I am trying to map their network and there are no descriptions to the ports, and there are allot of changes. I will follow the mac address and let you know. Thank you!

[Mark Malone · Accepted solution]

Yes but when you follow the macs it will bring you to each edge port , it will show you what interface its learned from exactly, then do a show cdp neighbour for that interface jump onto that switch then run the show mac again and it will provide a new port and so on until it reach's its original access port depending how big the l2 domain is , you need to do it with both macs as following the l3 ip is irrelevant as it exists in 2 places , but the mac is unique to each device so when you find the edge you can change one of the devices ips and that will remove the alert form logging automatically as it wont see a conflict anymore , that's the only true way of finding it as you said they ports are not labelled or have a valid description , its tedious but ill get you to the point where you can fix it , good luck

[fotismark]

Found out that the same IP on Switch A floor 192.168.100.11 which is the management, I have followed the Mac address down to each Port channel/cdp nei,

and found out that Mac Address belongs on to an SG300 Switch on basement.

So I believe they gave the same IP on management on that SG300 (which I do not have remote access).

Thankl you!

[Mark Malone · Accepted solution]

Yes that would do it , least you know now where to put the fix in when you n
get access , that's good

[fotismark]

Thanks!
BTW since you are the only one that is answering :) can you assist with another issue/problem, that I have?
1st: What course in CCNP covers the dialer interfaces, ppoe, adsl/vdls connection and debugging.
2nd: Where can I search regarding building VPN and connecting with a vpn client especially when it includes NAT. It 's an issue I am trying many day to overcome but nothing and I have tried many configs. Can you take a look?
https://supportforums.cisco.com/t5/vpn/vpn-help-nat-acl/m-p/3223515#M119487

Thank again!

[Afroz Alam]

Jan 7 07:28:22.209: %IP-4-DUPADDR: Duplicate address 192.168.34.250 on Vlan34, sourced by 0050.e804.62a6

Please explain what is the meaning of this message and help to resolve the same.

[Georg Pauwen]

Hello,

the MAC address belongs to a Cisco device, my best guess is that someone has assigned a duplicate management IP address to one of the switches..

[Afroz Alam]

I have searched but this mac address is not showing in my device. how can I find who has assign this ip address. Please suggest...

[Georg Pauwen]

Hello,

tough one, if you cannot find the MAC address. Typically, you would look at the MAC address table and track down the port(s) where that MAC address is coming from. Can you ping 192.168.34.250 ?

[Afroz Alam]

yes pinging.

[Afroz Alam]

yes I have run mac address command same mac address is showing multiple times on different different vlan. so how I resolve this message. Please suggest...

[Georg Pauwen]

Hello,

how big is your network, how many switches do you have ? Are your clients getting their IP addresses from a DHCP server ?

[Afroz Alam]

actually my company is hospitality and there are 80 apartments apart from office and In each apartment is 12 port POE switch which is manage from core switch and for each floor separate vlan is configured &  In each apartment AP installed and all AP managing from cisco controller and this message is showing in my controller system logs.(Jan 7 07:28:22.209: %IP-4-DUPADDR: Duplicate address 192.168.34.250 on Vlan34, sourced by 0050.e804.62a6) but no any network issues here.