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.


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. 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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.