My localhost webserver told me that it could not let me access any pages because I browsed from another machine.
Since I am so sure that I sat down on the same machine, i.e. my notebook, as this webserver, I wondered and think it was unbelievable.
However, using Wireshark to catch packages, I found that it real! .. I used an source IP address of global network to connect with localhost network. How surprising!
After trying for while, I got the cause. The source IP address was changed, so that I set an ‘IPTABLES’ rule wrong.
It masqueraded all packets from my computer without filtering, ever local packets to localhost.
So, I changed it as a following rule.
-t NAT -A POSTROUTING -j MASQUERADE
-t NAT -A POSTROUTING -j MASQUERADE -s 192.168.3.0/24