Hot Standby Router Protocol

Nov 12 2008   12:56PM GMT

Solution for %IP-4-DUPADDR: Duplicate address error log in your Cisco 6500 Switches running HSRP

Posted by: Yasir Irfan
Switches, Cisco, Switching, Routing and Switching, Cisco IOS, WebEx, Hot Standby Router Protocol, HSRP, Cisco 6500, Cisco Tips, Cisco Learning, Network Troubleshooting, Cisco Systems, Cisco 6500 Series Catalyst Switch, Cisco Catalyst 6513 Switch, Cisco Support, TAC

Dear Friends In my previous post I was talking about the HSRP error generated in Cisco 6513 Switches with a Duplicate IP Address. I did open a TAC case with Cisco Systems. I should first of all salute Cisco for the great support to solve this issue.  Cisco TAC Engineer Mr. Pradeep was in constant touch with me in this case to resolve the issue. The best part of their support is the use of technology. Mr. Pradeep initiated a Web Ex meeting with me and spent more than hour to check step by step.  He helped me a lot and did learned lot of things from Cisco TAC team, like how to approach the problem and what measures should be taken to trouble shoot any problem. Finally we came to the conclusion there are no bugs or errors in the IOS we are using. There are no problems either in hardware or in the current configuration.I would like to quote the solution provided Mr. Pradeep TAC Engineer, Cisco Systems “Let me summarize this issue. You told me that there is one Trojan affected PC/ Host, which is connected to your access switch. Further, you got some duplicate IP address messages on your core switch. During troubleshooting, I have checked and verified that the Cisco’s Switches are working fine. Their configurations were correct. Generally duplicate IP addresses can be impounded by “broken HSRP links” or “incorrect DHCP pool configuration”, or by misconfiguration of switches or STP. I found that this entire setup is configured correctly. Furthermore, I would like to inform you that Cisco’s IOS cannot resolve Trojan issue on any PC. PC has got its own Operating System, and IOS can work only and only on “Cisco’s device”

 So now it’s quite clear if you face this kind of problem make sure the infected PC is removed from the network and make sure it s free from any sort of Trojans or Virus.

Nov 9 2008   6:51AM GMT

Don’t panic whenever you see %IP-4-DUPADDR: Duplicate address error log in your Cisco 6500 Switches running HSRP

Posted by: Yasir Irfan
Networking, Switches, Cisco, Switching, Routing and Switching, Hot Standby Router Protocol, HSRP, Cisco 6500, Cisco Tips, Network Troubleshooting, Trojan, Cisco Systems, Cisco 6500 Series Catalyst Switch, Cisco 6503, Cisco Catalyst 6503-E Switch, Cisco Catalyst 6506-E Switch, Cisco Catalyst 6509-V-E Switch, Cisco Catalyst 6509-E Switch, Cisco Catalyst 6513 Switch

If you are running HSRP and one of your VLAN is down and the following errors are generated in your Switch don’t panic. All this happens due the Trojans in the network.

MBGF-DAC-6500-BB01#sho log

Nov  9 07:54:21: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:54:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:55:22: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:55:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:56:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.1 256 packets

Nov  9 07:56:22: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:56:52: %IP-4-DUPADDR: Duplicate address 10.12.0.1 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:57:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.2 263 packets

Nov  9 07:57:11: %SEC-6-IPACCESSLOGS: list 12 permitted 10.0.0.7 200 packets

Nov  9 07:57:22: %IP-4-DUPADDR: Duplicate address 10.12.0.1 on Vlan106, sourced by 000f.fe0a.1fbc

Nov  9 07:57:52: %IP-4-DUPADDR: Duplicate address 10.12.0.2 on Vlan106, sourced by 000f.fe0a.1fbc

MBGF-DAC-6500-BB01#

Last week at 3 A.M I received a call from our Help Desk, stating our applications are not running in one our departments. I logged remotely to our Network and try figured out what is problem. Upon carefully looking at the logs in our Cisco 6513 core Switches I figured out a duplicate IP address is created which happens to be the Standby IP address for the Core Switch for HSRP.

I figured out the PC by looking the at mac address generated in the log and closed the network connection for that particular PC and the problem was solved.

If you face similar problems its better to change the HSRP Standby IP address in Core Switches and then try figure out the infected PC. Once the PC is figured out close the network connection and make sure the Trojans are removed. Upon cleaning the infected PC you can reconfigure the HSRP Standby IP address to the previous one.

Once I get the complete solution to fix this problem I will post it.