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New Member

IPv6 Duplicate error msg on GNS3

Hello,

 

I am trying IPv6 Lab on GNS3,   but I am again and again getting the following duplicate error message on my GNS3 router,

 

%IPV6-4-DUPLICATE: Duplicate address FE80::C000:13FF:FE80:0 on FastEthernet0/0

 

I tried changing my Interface Link-Local address, but no result, Please let me know how to get it resolved ?

14 REPLIES
Cisco Employee

Hi,I suppose you are running

Hi,

I suppose you are running multiple routers in GNS3.

Can you please post the configuration of the routers that are connected together via the Fa0/0 interface as shown in the log message you have posted? The Fa0/0 interface configuration will suffice. Please also post the output of the following command from both routers:

show interface fa0/0 | i bia

Best regards,
Peter

 

New Member

Hi Peter,I am not running

Hi Peter,

I am not running multiple routers.  I have only one router connected to Virtual-Box cloud and it is connecting to Virtualbox Win-7.

 

and this is the output of commad

R1#sho int fastEthernet0/0 | i bia
  Hardware is Gt96k FE, address is c200.1380.0000 (bia c200.1380.0000)

Cisco Employee

Hi,I am not sure I understand

Hi,

I am not sure I understand your setup. If you are running only one router then it cannot cause an IPv6 address conflict with itself.

Can you describe your topology more closely please? I am guessing that you have a router instance in GNS3 that connects to some VirtualBox instance under the same GNS3. Is that correct? Is there any possibility that either the VirtualBox NIC uses the same MAC address as the router, or that the frames sent by the router are bridged back to it? Perhaps you could try sniffing the link between the router and the VirtualBox, record the traffic in Wireshark and post it here for further analysis.

Best regards,
Peter

 

New Member

Yes your guess is right,  I

Yes your guess is right,  I have a single router connects to Virtual-Box Win-7.  I even tried changing the router interfaces, changing the router int  Link-Local addresses, changing the whole router and put new series Router,  but still im getting same duplicate-add message.

 

I did some sniffing, plz see the attached

Cisco Employee

Hello,Thank you for attaching

Hello,

Thank you for attaching the packet dump.

I have noticed something strange: all packets sent by your router are duplicated, as if they were sent out and subsequently received back. For example, check the CDP messages: two of them are recorded precisely at time 34.44, other two at time 42.277, yet another two at time 44.615, and so on. There is also a duplicated ICMPv6 Neighbor Solicitation sent by your router at time index 44.69. If somehow this message was reflected back to the router, it could have possibly triggered the IPv6 address conflict on the IOS.

Interestingly, packets sent by your VirtualBox machine are not duplicated, only the router's are.

How exactly is the interconnection between the router and the VirtualBox accomplished? Is there an emulated switch inbetween, or is it done over some kind of bridging?

Are you running the newest GNS3 and dynamips? There was a bug in older versions that could possibly cause packet looping between routers on the same segment. While this does not precisely resemble the behavior, let's make sure you're running the newest GNS3 before trying anything else.

Best regards,
Peter

 

 

New Member

Hello, I am using a switch in

Hello,

 

I am using a switch in between my router and VirtualBox.   Also I tried same scenario on latest versions of GNS3  0.8.3 and 0.8.7.  but unfortunately same duplicate-messages comes on both versions

 

Regards,

Cisco Employee

Hi,Can you try simplifying

Hi,

Can you try simplifying the scenario and connect the router and the VB directly somehow? I am not using GNS3 myself - I am totally fine with dynamips+dynagen although the flexibility of the GUI is sometimes missing.

Best regards,
Peter

New Member

 I connected both directly 

 

I connected both directly  the VB and Router,  but still same duplicate-message

 

Regards,

Cisco Employee

Hi,Okay. If you forgot about

Hi,

Okay. If you forgot about the VB for a moment and simply connected two routers in back-to-back fashion over their FastEthernet interfaces in GNS3, would you still see the IPv6 duplicate address?

Best regards,
Peter

New Member

when I connect to routers, 

when I connect to routers,  no duplicate-message comes in-between them. duplicate message comes on that interface which connects to my VB

Cisco Employee

Hi,I was unable to replicate

Hi,

I was unable to replicate this issue in my quick-and-dirty GNS3 setup. I have a c2691 router running against a Debian in VirtualBox, directly connected to each other. I had no troubles with the duplicate address message, there were no duplicate messages recorded in the packet capture, and the connectivity between the Debian and the router was working without problems.

I am wondering - what operating system are you at? Is it Linux or Windows? Have you actually tried restarting your whole computer? The connection between the VirtualBox and the GNS3 appears to be accomplished over UDP sockets, and I have a feeling that there might be a problem in the communication between the GNS3 and the VirtualBox.

Just curious: what exact interface did you perform the captures you have posted - was it the router's interface or the VB's interface?

Best regards,
Peter

 

New Member

 I got the duplicate-message

 

I got the duplicate-message resolved by adding the following interface command on my router

ipv6 nd dad attempts 0

 

Regards,

 

Cisco Employee

Hi,Unfortunately, you have

Hi,

Unfortunately, you have not solved the problem - you have only deactivated the mechanism that reports the problem. The issue with the packets sent by your router looping back to the same router persists, and it may cause another problems in future. I caution you against running your setup like this, especially if you use it for learning - because of the packets being fed back to the router, the behavior of your topology may be different.

Just curious: when you run your router attached to the VirtualBox instance for some time (more than one minute) and reports the IPv6 address conflict (i.e. without the workaround you've suggested earlier), what does the show cdp neighbor show? Does this input contain an entry about this very router? If yes, it definitely confirms the packets being reflected back to the router for some obscure reason.

Do you perhaps have an option of running your GNS3 on another machine, or on another operating system? At this point, I am fairly sure that the problem is somewhere in the way GNS3 ties together a VirtualBox instance and an IOS router instance. However, this is not about solving IOS issues anymore (and it never was as it turns out), this is about possible issue in GNS3 or in your particular setup. Unfortunately, there are many variables in play, including the precise settings of GNS3, VirtualBox, your particular operating system and the software running on it.

Best regards,
Peter

 

New Member

But after deactivating of

But after deactivating of Deed-peer-detection, the message is disapeared plus the issue is also resolved. And yes the "show cdp neighbor" command output shows entries about this router. it is with the work-arround it did and without that aswell, in both situations it shows entries about this Router itself. Currently i dont have another windows / pc to test this tephology, but i will try it later
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