Eclipse error undefined reference to pcap function

I had the same problem in Eclipse. I order to link this library to your project, right click the project in "Project Explorer" (short view) and choose "Properties". On the left go to "C/C++ Build" > "Settings" and on the "Settings" panel go to "Tool Settings" > "GCC C Linker" (if this is your compiler) > "Libraries" > and add the word "pcap" in the list titled "Libraries (-l)". Press "Apply" on the bottom and then "OK". Click "Project" > "Build All" and this should do the job. It should be no errors now. :)