From server cannot ping server itself by its hostname while can ping by its IP

Question

I host an ubuntu server at a data center and worked well for years till last night the server can not ping itself by host name. No config has been changed. Here are what it can/can not do now.

• From outside, I can ping the server both by its static IP, and by its hostname.
• From server, I can ping any website (google, yahoo, ...).
• From server, I can ping localhost, and can ping the IP of server itself.
• From server, I can not ping sever itself by its hostname.

Here is /etc/network/interfaces:

source /etc/network/interfaces.d/* 

auto lo
iface lo inet loopback

auto enp5s0

iface enp5s0 inet static
address xxx.xxx.xxx.134
netmask 255.255.255.128
broadcast xxx.xxx.xxx.255
gateway xxx.xxx.xxx.129
dns-nameservers 192.168.1.1 8.8.8.8 8.8.4.4

and /etc/resolv.conf:

nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 192.168.1.1
nameserver 8.8.8.8
nameserver 8.8.4.4

and /etc/resolvconf/resolv.conf.d/head:

nameserver 8.8.8.8
nameserver 8.8.4.4

and the output of route -n is:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         xxx.xxx.xxx.129 0.0.0.0         UG    0      0        0 enp5s0
xxx.xxx.xxx.128 0.0.0.0         255.255.255.128 U     0      0        0 enp5s0
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0

These configs worked for years. Wondering what happened? Thanks.

Answer 1

Check /etc/hosts. Probably there's a line with the name of the server and an incorrect IP