Week3 Programming Assignment

Bug: For fanout=3, causes the following error and later crash on
accessing h27 node in submit.py

*** defaultIntf: warning: h20 has no interfaces
*** defaultIntf: warning: h21 has no interfaces
*** defaultIntf: warning: h22 has no interfaces
*** defaultIntf: warning: h23 has no interfaces
*** defaultIntf: warning: h24 has no interfaces
*** defaultIntf: warning: h25 has no interfaces
*** defaultIntf: warning: h26 has no interfaces
*** defaultIntf: warning: h27 has no interfaces