Duplicate IP address Conflict between an AIX and Windows 2003 Server

Hello,

My AIX Admin and telling me his new AIX Server is having an IP address conflict with one of my Windows 2003 servers that has been up for over a year now.   We have hundreds of Windows 2003 servers so I confused why his AIX is having an issue with this one windows  server.  

Here are the details from his AIX log.
===========================================
LABEL:          AIXIF_ARP_DUP_ADDR
IDENTIFIER:     FE2DEE00

Date/Time:       Mon Apr 12 15:49:28 EDT 2010
Sequence Number: 6358
Machine Id:      00C734C54C00
Node Id:         AIX1
Class:           S
Type:            PERM
WPAR:            Global
Resource Name:   SYSXAIXIF

Description
DUPLICATE IP ADDRESS DETECTED IN THE NET

Failure Causes
ARP RESPONSE RECEIVED FOR MY IP ADDRESS

        Recommended Actions
        CONTACT NETWORK ADMINISTRATOR

Detail Data
DUPLICATE IP ADDRESS
0a48 0093
MAC ADDRESS
0021 5E96 679c
=================================================
Specs
Windows 2003 Server  - IBM Blade Chassis #1 - Blade  Slot #3 - connected to SAN
AIX Server     -  IBM Blade Chassis #2 - Blade Slot 5 -connected to SAN

Can somone explain what might be going on here?

Thanks,

Capt
capt_morganAsked:
Who is Participating?
 
madunixConnect With a Mentor Commented:
am listing the link:
       
errpt output shows: AIXIF_ARP_DUP_ADDR and error description is: DUPLICATE IP ADDRESS DETECTED IN THE NET

Problem(Abstract)
Why am I logging an error in the errpt for a duplicate ipaddress.
 
Symptom
LABEL:          AIXIF_ARP_DUP_ADDR
IDENTIFIER:     FE2DEE00

Date/Time:       Thu Jan 1 12:00:00 2008
Sequence Number: 1012
Machine Id:      XXXXXXXXXXXX
Node Id:         clkdns1
Class:           S
Type:            PERM
Resource Name:   SYSXAIXIF

Description
DUPLICATE IP ADDRESS DETECTED IN THE NET

Failure Causes
ARP RESPONSE RECEIVED FOR MY IP ADDRESS

       Recommended Actions
       CONTACT NETWORK ADMINISTRATOR

Detail Data
DUPLICATE IP ADDRESS
<hex number>

MAC ADDRESS
<hex number>

 
Resolving the problem
The reason you are logging this error in the errpt is due to the fact that AIX has received an ARP broadcast/unicast packet from another server.  That other server sent out a "gratuitous ARP" (gratuitous meaning it was not asked for by AIX).  This arp packet that AIX received indicated that another machine on the AIX subnet is using this ipaddress.
Normally you can take the <hex number> under the field: "MAC ADDRESS" in the errpt to your network admin, and find out which machine it is, and see if it is using the same ip as AIX.

There is currently a situation where AIX will receive an ARP packet from a Windows OS box that will look like an ARP telling AIX that the ip is already in use.  However, the Windows server is not using AIX's ipaddress.  This is a defect with the Broadcom adapter in the Windows server that causes this problem. This only happens when the Broadcom adapter is set up for Teaming in a Active/Active configuration.  

Please see below link:
http://www-947.ibm.com/systems/support/supportsite.wss/docdisplay?lndocid=MIGR-5075064&brandind=5000020

As a workaround to force the Windows server to stop sending AIX a gratuitous ARP packet, you must put the Windows in a Active/passive teaming configuration.  Another solution would be to unteam the adapters all together in the Windows server.  See broadcom for any device driver updates that may also provided a solution.  There is not any misconfiguration or problems on the AIX side.  

If AIX receives a gratuitous ARP from another Server that says that the other server is using AIX's ip, then the message will be logged in the errpt, there is no way to disable this on the AIX side.

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woolmilkporcCommented:
Well,
at first sight I'd tend to think that your AIX admin mistakenly used one of the Windows servers' addresses, either a static one or one out of your DHCP's scope.

wmp
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acl-puzzCommented:
suppose ip confilct ip  is 192.168.1.100 then simply add this ip in MAC based reservation in DHCP scope
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j-horbCommented:
Try

ping -a 10.72.0.147

this might tell you which of your servers is clashing with the AIX system
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capt_morganAuthor Commented:
acl-puzz,

Just curious.  How is adding the IP to the DHCP going to help?  We don't use DHCP for servers sicne they are statically assigned.  
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carlmdCommented:
First I would check the lan interfaces on the AIX box with the command:
      ifconfig -a
This will show you all the lan cards (en?) and all ip addresses assigned to them. One of these should show you the duplicate ip address. If this ip is new to the AIX box, then pick a different one to resolve the problem. If not new then this ip must have recently been added to the windows network.

Now lets find the ip on the network. On the AIX box type:
   arp -a
and look for the duplicate ip address. You should see the name and mac address of the offending windows system. Then simply change it's ip address and you have solved the problem.

If you don't see the ip there then it is possible it was on the network for only a short time (DHCP?) and has been removed. If such be the case then the error should go away the next time you reboot the AIX system.

Regarding you request for clarification on DHCP, I think what is intended is to prevent the windows network from assigning this ip address to a pc using DHCP, not the AIX system. This assumes that all systems share the same ip address range.
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rajpaddaCommented:
Seems like IP address configured on the AIX server is conflicting with already configured IP address on windows server. MAC address of NIC on which the IP is configured is "0021 5E96 679c" ask your network administator to have look into this to see if the IP is logging against two different MAC addresses? If reqd get different IP address for the system whichever AIX or windows is built later
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