I spent few hours solved a network issue which caused by wrong MTU setting.
the symptom is my VM can not access some of the website.
for example. curl to https://packages.cloud.google.com will hang.
the problem looks like related with the MTU setting.
it is MTU problem confirmed with ping -M do which means do not fragment.
then change interface mtu to 1380 solved problem.
now the problem solved.
the root cause is actually due to the vpn tunnel in the routing path which as MTU set to 1380.
