[ns] Undefined Symbol

[Anuj Goel <goel@eamri.rpi.edu>]

Hi, I am getting the following error 

Undefined                       first referenced
 symbol                             in file
et_ns_ptypes                        tclAppInit.o
ld: fatal: Symbol referencing errors. No output written to ns

I am getting this error even after the following declaration In the
tclAppInit.cc file.
 
     extern EmbeddedTcl et_ns_ptypes;

Also if I do "make depend", it says,

emulate/ether.cc:46: net/ethernet.h: No such file or directory
emulate/arp.cc:50: net/ethernet.h: No such file or directory
emulate/net-pcap.cc:60: pcap.h: No such file or directory

Where can I find ethernet.h and pcap.h. Thanks in advance,

Regards,
Anuj.