[Novalug] question on tcpreplay

James Ewing Cottrell 3rd JECottrell3@Comcast.NET
Sun Aug 14 17:48:20 EDT 2011

  As far as the "other network" problem, I would place secondary 
addresses on the machines you are trying to connect to so they look like 
they are on the same network.

One problem you are going to have with any replay is that the other side 
is likely to do things differently. This is obvious for the other side's 
initial sequence number, but it's also possible that acks and window 
sizes as well as timeouts may happen differently.

TCP is a bit more complicated than say, replaying an SMTP or even a Web 
transaction back.

Hopefully, tcpreplay has some AI built into it to adapt, but I wonder.


On 7/31/2011 5:36 PM, Andy Tornquist wrote:
> Does anyone have experience with replaying tcp traffic to test an 
> application? We are trying to test an application we have captured the 
> necessary traffic in a test environment. We are using tcpreplay to 
> replay this pcap file  on another server that is on another network.
> The application generating traffic is on network a.b.c.d , The server 
> recieves the traffic and is proccessed by the application properly. We 
> have used tcpdump and wireshark to generate a pcap.
> We move the pcap file to another network and use tcpreplay to play the 
> traffic locally on another server on network a.b.c.e. The traffic is 
> seen in a tcpdump. We have written a ruby script that listens on the 
> network socket and prints out a message when ever a packet received. 
> The script will not display the messages when a file from another 
> network is played.
> We have reconfigured the network interface to be on the same network 
> as the pcap file but no success.
> Anyone have any ideas or suggestions?
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