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Path MTU black holes can result in network performance/connectivity issues

Last Updated:

Applies to

Environments where endpoints support a larger MTU(Maximum Transition Unit) than the smallest MTU in the path.


  • User environments where Path MTU is not successfully discovered can experience issues with both network performance as well as general connectivity issues.
  • The performance issues might stem from intermediate devices performing IP fragmentation on large MTU packets, or endpoints having to reassemble.
  • Connectivity issues usually occur when a large MTU frame fails to traverse the network, leading to the re-transmission of this packet until one of the endpoints gives up and resets the connection.


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