This is our old Q&A Site. Please post any new questions and answers at

Question: We are getting a lot of Expert(error notifications) about TCP Retransmissions, Reassembly error; New Fragment overlaps old data.(retransmission?).

The offending packets are happening between a hyperV node and the VMM. Should we be concerned or is this is false positive.

both servers are plugged in to the same switch, the hyper V node has a dedicated port and virtual network created for our server lan. The vmm is just a server that sits on the same vlan natively.


3035    0.983810000 TCP 318 Note    [TCP Retransmission] 52503→5985 [PSH, ACK] Seq=2407 Ack=2911 Win=4100 Len=264
3036    0.983863000 TCP 1514        [TCP segment of a reassembled PDU]
3037    0.983864000 TCP 1514    Note    [TCP Retransmission] [TCP segment of a reassembled PDU]
3038    0.983865000 HTTP    736 Error   POST /wsman HTTP/1.1 [Malformed Packet]
3039    0.983866000 TCP 736 Error   [TCP Retransmission] 52503→5985 [PSH, ACK] Seq=4131 Ack=2911 Win=4100 Len=682[Reassembly error, protocol TCP: New fragment overlaps old data (retransmission?)]

asked 05 May '15, 13:21

Quorrum's gravatar image

accept rate: 100%

edited 05 May '15, 14:03

Jasper's gravatar image

Jasper ♦♦

also check the switch ports and there are no errors.

(05 May '15, 13:22) Quorrum

sounds more like false positives... but maybe you can upload a capture file at and post the link here? It's easier to check a trace than some ASCII dump.

(05 May '15, 14:05) Jasper ♦♦

here is a chopped, cap. Any help with this is appreciated.

(06 May '15, 08:17) Quorrum

my issues are the dup ACk's and ReTransmissions. These seem like waste of band... Should i be worried about these.

(06 May '15, 08:19) Quorrum

we are chalking these up to false positives and microsoft doing some thing as usual that they are not supposed to be doing.

permanent link

answered 07 May '15, 13:08

Quorrum's gravatar image

accept rate: 100%

Well, since every frame is seen twice, did you by any chance capture on a span-port with the source being a vlan? Then it is a capturing artefact as every frame with first enter the vlan and then exit the vlan. When capturing on a vlan, better use "rx only" instead of "both".

permanent link

answered 08 May '15, 04:06

SYN-bit's gravatar image

SYN-bit ♦♦
accept rate: 20%

monitor session 1 source vlan 100 monitor session 1 destination interface Gi9/18 monitor session 1 filter packet-type good rx

only isnt an option.

ad.m.1(config)#monitor session 1 filter packet-type good rx ? <cr>

(08 May '15, 10:20) Quorrum

good idea i was under the assumption that is was only. i will look in to that.

(08 May '15, 10:21) Quorrum

I don't have a cisco switch at hand, but it should be something like:

monitor session 1 source vlan 100 rx
monitor session 1 destination interface Gi9/18
(08 May '15, 10:39) SYN-bit ♦♦
Your answer
toggle preview

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here



Answers and Comments

Markdown Basics

  • *italic* or _italic_
  • **bold** or __bold__
  • link:[text]( "title")
  • image?![alt text](/path/img.jpg "title")
  • numbered list: 1. Foo 2. Bar
  • to add a line break simply add two spaces to where you would like the new line to be.
  • basic HTML tags are also supported

Question tags:


question asked: 05 May '15, 13:21

question was seen: 3,151 times

last updated: 08 May '15, 10:39

p​o​w​e​r​e​d by O​S​Q​A