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Cisco ISR is reporting

%FW-4-TCP_OoO_SEG: Dropping TCP Segment: seq:1979009128 1500 bytes is out-of-order; expected seq:1978984512. Reason: TCP reassembly queue overflow - session

I have adjusted config up to these limits to no avail:

ip inspect tcp reassembly memory limit 4096 
ip inspect tcp reassembly queue length 1024

This is occurring on traffic originating from the Internet or from a GRE tunnel, resulting in application timeout and rather slow download speeds.

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There are a few things you can adjust for this. I had to do this on a router:

ip inspect tcp reassembly queue length <length>
ip inspect tcp reassembly timeout <timeout>
ip inspect tcp reassembly memory limit <limit>

You don't seem to have adjusted the timeout.

  • I had to raise the timeout to 40 seconds to stop this condition. Does that seem reasonable? Or is it an indicator of some larger problem. – stephen muth Nov 9 '15 at 20:37
  • You could be receiving a large number of out of order packets. This could be caused by any number of things, but will be a common problem with load balancing done incorrectly. I think 40 seconds isn't too bad. – Ron Maupin Nov 9 '15 at 20:40

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