Linux can ping IP addresses, but cannot ping domain names.

Linux can ping IP addresses, but cannot ping domain names.

I encountered a problem today. I can ping the IP address and cannot ping the domain name. I thought it was a problem with the DNS resolution server. I have been searching for a long time. The problem is not here.

[root@www postfix]# cat /etc/resolv.confnameserver 202.96.209.133options attempts:1 timeout:1 rotate#nameserver 10.202.72.117nameserver 10.202.72.118nameserver 114.114.114.114nameserver 8.8.8.8[root@www postfix]# 

After reading the route table, the problem is not on the routing gateway.

[root@www postfix]# netstat -rnKernel IP routing tableDestination     Gateway         Genmask         Flags   MSS Window  irtt Iface115.28.80.0     0.0.0.0         255.255.252.0   U         0 0          0 eth110.163.176.0    0.0.0.0         255.255.240.0   U         0 0          0 eth0169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth1192.168.0.0     10.163.191.247  255.255.0.0     UG        0 0          0 eth0172.16.0.0      10.163.191.247  255.240.0.0     UG        0 0          0 eth010.0.0.0        10.163.191.247  255.0.0.0       UG        0 0          0 eth00.0.0.0         115.28.83.247   0.0.0.0         UG        0 0          0 eth1[root@www postfix]# [root@www postfix]# [root@www postfix]# [root@www postfix]# [root@www postfix]# routeKernel IP routing tableDestination     Gateway         Genmask         Flags Metric Ref    Use Iface115.28.80.0     *               255.255.252.0   U     0      0        0 eth110.163.176.0    *               255.255.240.0   U     0      0        0 eth0link-local      *               255.255.0.0     U     1002   0        0 eth0link-local      *               255.255.0.0     U     1003   0        0 eth1192.168.0.0     10.163.191.247  255.255.0.0     UG    0      0        0 eth0172.16.0.0      10.163.191.247  255.240.0.0     UG    0      0        0 eth010.0.0.0        10.163.191.247  255.0.0.0       UG    0      0        0 eth0default         115.28.83.247   0.0.0.0         UG    0      0        0 eth1

Then let's take a look:

[root@www postfix]# grep hosts /etc/nsswitch.conf#hosts:     db files nisplus nis dns#hosts:      files dnshosts:      dns files

I changed it to dns first. After files is tested, it still doesn't work.

Finally, I found that it was the reason for the firewall. I enabled the firewall, which caused the ping domain name to fail.

Port 53 is used for domain name resolution. You need to configure the following settings in the firewall.

iptables -A INPUT -p udp --sport 53 -j ACCEPTiptables -A OUTPUT -p udp --dport 53 -j ACCEPTiptables -A INPUT -p udp --dport 53 -j ACCEPTiptables -A OUTPUT -p udp --sport 53 -j ACCEPT

In this way, you can ping the domain name.

In Linux, IP addresses can be pinged, but domain names cannot be pinged. How can this problem be solved?

Add something in/etc/resolv. conf

The format is as follows:
Nameserver xxx. xxx
Nameserver xxx. xxx
The following IP address is the address of the dns server. You can add multiple IP addresses.

Then
Ifdown eth0
Ifup eth0
Try again

What can I do if I can only ping the ip address on a linux Server when I cannot ping the domain name?

Does your DNS resolve the IP address of the linux server?