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New Member

Duplicate IP in VLAN

I am geting the below error on one of our Coreswitch MSFC. The IP (X.X.X.X) is placed as standby IP for VLANX. The same IP is assigned for backup Core switch as standby. There is no such error for other VLANs which is having same kind of standby IP

Please help me how to fix it.

%IP-4-DUPADDR: Duplicate address X.X.X.X on VlanX, sourced by <MAC - Address>


Re: Duplicate IP in VLAN

New Member

Re: Duplicate IP in VLAN


There is no information abt "%IP-4-DUPADDR". They have explained abt "%STANDBY-3-DUPADDR". I belive its different.

Eventhough the error message is different I suspect some STP loop. Because when I am doing the tracert, getting more then one hop for same IP.





1 1 1 y.y.y.y

* * * x.x.x.x

* * * x.x.x.x

* * * x.x.x.x

Trace Complete.

Note: this is happening for sometime only not always.

Please help me to fix this.

Thanks in Adv

Re: Duplicate IP in VLAN

Do you see any other HSRP messages along with the above error?

Would it be possible for you to trace the MAC address mentioned in the above error


New Member

Re: Duplicate IP in VLAN


The MAC is belongs to this VLAN

New Member

Re: Duplicate IP in VLAN

This MAC is listing for Multiple VLAN interfaces...


its confusing me...

New Member

Re: Duplicate IP in VLAN

Is that something like this ?

SWINFOR_1#show arp | include

Internet - 0016.474a.6c7f ARPA Vlan1

Switch_1#show mac-address-table address 0016.474a.6c7f

Unicast Entries

vlan mac address type protocols port


1 0016.474a.6c7f static ip,ipx,assigned,other Switch

1135 0016.474a.6c7f static ip,ipx,assigned,other Switch

The same MAC-Address is seeng in several VLAN's?, and on the "show arp | inc mac.mac.mac", it takes for a - agetime?

If u use a dhcp server for ip attribution, make a reserve for the route/switch, and/or server's range ip's.

%IP-4-DUPADDR: Duplicate address X.X.X.X on VlanX, sourced by

Is that source mac address, the same mac when u do "show arp | inc (ip duplicated)" command ?

If it is not, perform a show mac-add MAC, till to final switch port.

When u arrives the final switch port, ShutDown the port, and wait for complaints. :)

Before u shut down that port assure that is no more than 1 mac-address on that port, could be a switch or hub connected, without management.

New Member

Re: Duplicate IP in VLAN

Hi :

You could try 2 solution :

1. HSRP group ID make it one vlan one ID.

2. USE " ARP x.x.x.x y.y.y.y arpa alias "

x.x.x.x -> IP address : active and standby all

need to be config on self switch.

mean active switch config active

ip/mac pair, same as standby.

y.y.y.y -> MAC address.explain the same as


Hope this work !


Ted Wen.

New Member

Re: Duplicate IP in VLAN


I traced both the Core Switches. The MAC address is a Virtual address for VLANZ in Designated Switch. The Same MAC is assigned for more that one VLAN in non-Designated switch!!!

The VLAx MAC address is diff from this.

Will it be happen normaly? Is this related to this error msg?

As this error is our live core switch its bit urgent. Please help me.

Re: Duplicate IP in VLAN

Would it be possible for you to post the HSRP configurations


New Member

Re: Duplicate IP in VLAN

Config detail


sh stand vlanx

VlanX - Group X

Local state is Active, priority 130, may preempt

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.032

Virtual IP address is x.x.x.1 configured

Active router is local

Standby router is x.x.x.2 expires in 8.180

Virtual mac address is aa.aa.aa

1 state changes, last state change 1w6d

IP redundancy name is "hsrp-Vlx-x" (default)

Sh run vlanx

interface Vlanx

ip address x.x.x.1 alt ip address x.x.x.3

no ip redirects

no ip proxy-arp

ip route-cache flow

standby x ip x.x.x.100 alt standby x ip x.x.x.100

standby x priority 140 alt standby x priority 130

standby x preempt


New Member

Re: Duplicate IP in VLAN


any idea please...