I think OpenWRT is good to go. I have used it before for VoIP calls and never 
had a problem. Changing port numbers is not a problem as long as it is 
predictable. For example, if port 5000 source is always translated to 8000, not 
a problem. If the translation is unpredictable, then you have a problem.

Only older routers are affected. I had an old FreeBSD based router that didn't 
work, but we got rid of it a few years ago.

Fred.

From: Mike A <[email protected]<mailto:[email protected]>>
Reply-To: Main forum for tcpreplay 
<[email protected]<mailto:[email protected]>>
Date: Thursday, April 3, 2014 at 1:22 PM
To: Main forum for tcpreplay 
<[email protected]<mailto:[email protected]>>
Subject: Re: [Tcpreplay-users] Passing Traffic Through a Router using one Linux 
machine?

I'm actually using an OpenWrt router - perhaps there is a way to turn off or 
simplify the NAT so that it does not change port numbers?

Mike


On Thu, Apr 3, 2014 at 9:44 AM, Fred Klassen 
<[email protected]<mailto:[email protected]>> wrote:
If it was a router without NAT you could make this work provided that your 
hardware was identical to IP addresses/MAC addresses in the pcap file. If not, 
you will have to use tcprewrite/tcpprep to make it so.

With NAT there is an extra complication. When a connection is established, NAT 
will translate the source port number. The algorithm is different from one NAT 
to the next. What is difficult is if the translated source port is completely 
random with no relation to the original source port. Luckily those NATs are 
going by the wayside because they break TURN servers, and thereby break direct 
peer-to-peer VoIP calls (VoIP proxy required).

Provided the capture was done on the same NAT with the same source port 
translation algorithm, and the same care is taken to ensure that the addresses 
match the hardware, and the NAT supports TURN, you should be OK.

Fred.

From: Mike A <[email protected]<mailto:[email protected]>>
Reply-To: Main forum for tcpreplay 
<[email protected]<mailto:[email protected]>>
Date: Wednesday, April 2, 2014 at 7:11 PM
To: 
"[email protected]<mailto:[email protected]>"
 
<[email protected]<mailto:[email protected]>>
Subject: [Tcpreplay-users] Passing Traffic Through a Router using one Linux 
machine?

Hi,

I'm running tcpreplay 4.0.4 on Ubuntu Linux 12.  I've read the usage examples 
(http://tcpreplay.synfin.net/wiki/usage) and followed along.  I'm trying to 
replay a single-stream (one 5-tuple) pcap so that packets go through a router.

My hardware setup is involves one Linux machine (with eth0 and eth1) and one 
router (which does NAT):

     eth0 <-> LAN (router) WAN <-> eth1
192.168.0.1 <-> 192.168.0.2 (router) 10.0.0.2 <-> 10.0.0.1

* Will this physical setup work? Or are there common pitfalls or mistakes?
* For packets that have src IP 192.168.0.1 and dst IP 10.0.0.1 (both on the 
linux machine), will the Linux OS short-circuit and simply pass packets 
internally (and not actually send it out to the router?)?


If I can get tcpreplay to actually send packets from a pcap through a router I 
will donate $ to whoever or whatever, because this will be the most useful 
tool.  It's something I have needed for such a long time, and will get used a 
lot.

Thanks ahead for any help,
Mike

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