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Snooping TCP packets for fixed IP systems


I am not an expert in networking but I am trying to connect two embedded systems in a network to snoop the TCP packets. Both the systems(lets say A and B) has fixed IP address and they communicate on a dedicated port. I am using PC (lets say system C) and Wireshark to snoop the TCP packets for debugging.

1) When I connected these systems(A,B and C) through a switch, I couldn't see any data on Wireshark. After some Googling I found that now a days switches are smart and they do flow control, that's the reason I couldn't see any data on the Wireshark.

2) I connected both the embedded systems (A and B) via USB to Ethernet adapters(one for each system) to a PC(system C) on which I was running wireshark. In Windows 7 there is an option to link both the network adapters via bridge, which I did by right clicking both the adapters and creating a bridge. I couldn't ping from system A to system B or vice-verse.

I just want to snoop the TCP packets on wireshark from these systems on a PC with out any switches(external hardware), is there any other way I can snoop the packets easily ? Your help would be appreciated tremendously and thanks in advance.


asked 21 Jun '13, 02:14

embdsp's gravatar image

accept rate: 0%

One Answer:


See the Wiki page on Capture Setup.

If you have two network adaptors in the Win 7 system (one should not be a USB one), then you can bridge the two and capture on the non-USB NIC.

In this sort of situation the easiest method is to buy a switch that will span or mirror a port to a monitoring port. The Netgear ProSafe Plus GS105E can be picked up cheaply from Ebay (other models of switches are available) and will do this. If buying a switch for this purpose make sure it can span or mirror, a basic switch won't do this, hence the need to pay a little more. The switch will come in handy for all sorts of things in the future.

answered 21 Jun '13, 06:58

grahamb's gravatar image

grahamb ♦
accept rate: 22%

I will buy the switch which you ahve recommended. This seem to be hassle free idea. Thanks for your help.

Cheers! Emb

(21 Jun '13, 09:39) embdsp

I got mine from an EU ebay seller for GBP 28 delivered. A bargain.

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(21 Jun '13, 09:44) grahamb ♦

Million thanks for you suggestion, I will go for the switch. Thanks again. Cheers! Emb

(21 Jun '13, 10:35) embdsp