Friday, 17 September 2010
Dynamips/Dynagen and Wireshark
One of the things I've picked up from my INE MPLS CoD, is how useful Wireshark can be as a learning tool, especially when using Dynamips.
For example, it is exceptionally easy to start a capture on an interface in the middle of your topology, and see exactly what is going across the wire. This is helpful when looking at MPLS VPNs, and understanding the stacks of labels that are applied, and seeing the bottom of stack bit etc.
From your Dynagen window, the command for starting a capture is;
capture device interface filename [link-type]
'capture' starts the command
'device' is the Dynagen name of the device on which you want to run the capture, as seen from the 'list' command
'interface' is the interface on that device on which you want to run the capture
'filename' is the file where the capture will be saved (don't forget the .cap extension)
'link-type' is optional, and I've not yet played around with it myself.
To stop the capture, issue a no capture device interface command. The capture can then be opened up in Wireshark, and you can see all your networking glory ;-)
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