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  1. #1

    LInux dropping packets?

    Hi experts,

    We are running into an issue with some IPv6 trials where our JAVA application running on Redhat 5.3 (2.6.18 or higher) is not responding to IPv6 requests from the clients . We can see from the Wireshark that IPv6 request packets have arrived on the Linux host, but the packets are not passed up to our application! It seemed to us that Linux OS is dropping the packets after it receives them? We are hoping you may be able to help is with any insight, recommendations, or if there are Linux specific issues that you are aware of.

    This does not seem to be a routing issue as we are seeing the packets arrive at the Linux host and we can ping between the clients and the server. And the network engineer engaged in this issue indicated that they have disabled IPtable packet filtering as well as host based firewalls. The observation is that only client request packet that comes through to our application (our application actual receives the packets) is from the testing client on same subnet sourced from higher port numbers (>10000), not sure if this is a factor? The rest of the IPv6 requests from remote subnets are not being passed up to our application.

    And you think of any theories on why certain packets received by the Linux host might get dropped by the Linux OS? Or is it some Linux configuration that I am not aware of? I am not a Linux expert.

    Packet captures show that requests are being delivered to the host, but the our application does not show any incoming packets being read.

    Test clients were run on the local subnet and their requests were successfully handled by our application.

    I will list the IPv6 addresses for reference if it helps:

    Our application is on Linux with IPv6 address : 2001:558:1014:15:69:252:97:73

    Successful Test Client with IPv6 address : 2001:558:1014:14:69:252:97:10

    The failing client with IPv6 address : 2001:558:4000:10:215:a2ff:fe06:b9ab

    Any debugging ideas would be appreciated.



  2. #2
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Unfortunately, since my ISP (AT&T) isn't yet supporting IPv6 over their DSL services, I have not yet started testing IPv6 on my network. So, I don't know enough materially to help you. Have you checked the configuration and rules in your ip6tables setup?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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