Duplicate Packet Problem with bonding Linux

Unanswered Question
Jul 29th, 2010


    I'm facing a very serious problem with my one client.The network senario is given below:-

   Two cisco 6505  and two cisco 3750G switches are connected to each other on redundancy.HSRP is configured on cisco 6505 switches and both cisco 3750G switches connected with cisco 6505.

   cisco 3750 G switch is connected with servers and clients.In all servers and clients work on Linux with two ethernet ports.Bonding is configured with Linux clients and servers for redundancy.It is tested with one switch that bonding is working ok.

   When both LAN ports are connected with switch cisco 3750G, then no problem with applications.But when active port goes down then Duplicate packets recieved at clients and within 1 mint, application goes down.



I have this problem too.
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Nagaraja Thanthry Thu, 07/29/2010 - 05:58


When you say that the Primary interface goes down, I am assuming the link between the Linux Server and the switch. Does this issue happen with all clients or only with select few clients? I would look at the Linux server first to see if it is generating duplicate packets as the switches will forward only one copy of that packet to the clients.

Hope this helps.



siddindia Thu, 07/29/2010 - 08:49

Hi Nagraja,

    The Duplicate packet problem is in all servers and clients.

     So, I need urgent help in this problem.

      Is it possibility in problem in switche configuration?



Nagaraja Thanthry Thu, 07/29/2010 - 09:24


The chances of switch creating duplicate packets are very minimal. The only

possibility would be if there is a physical loop. Since you say that it

happens only when the link between the server and the switch goes down, I

believe it would be a server issue. One possibility is, when the link goes

down, it actually stays up and breaks the bonding resulting in a physical

loop. In that scenario, you might see the duplicate packets. You still need

to check the server to see if there is a way to make sure that the server is

not sending duplicate packets.

Hope this helps.



manish arora Thu, 07/29/2010 - 14:38

do you have ether channel configured on the switch side ? I have seen similar problem when you do bonding at linux server host but no configuration on the switch side ? please post your switch configuration as well as configure lacp standard ethernet bonding on linux host.




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