Dual-NIC virtual machine does not have Internet access problem: Unknown host www.baidu.com

Environment:

Configuration of two network cards, divided into intranet and external network;

Intranet: Host-only mode 192.168.142.140

External network: NAT mode 192.168.116.140

Configuration file:

NIC configuration file: [email protected] network-scripts]# cat Ifcfg-eth0 Device=eth0 Type=ethernet Onboot=yes Nm_controlled=yes Bootproto=dhcp [email protected] network-scripts]# cat ifcfg-eth1 Device=eth1 Type=ethernet Onboot=yes Nm_controlled=yes Bootproto=dhcp DNS configuration file: [email protected] network-scripts]# cat/etc/resolv.conf ; Generated By/sbin/dhclient-script Search Localdomain NameServer 192.168.142.1

Fault Description:

Ping Gateway and Baidu's IP can be ping, but ping Baidu's domain name www.baidu.com, return ping:unknown host www.baidu.com

Fault Analysis: DNS resolution issues

The IP address for Dhcp,dns was 192.168.142.1 occupied, the command line changed a lot of times no use

[[email protected]~]# Ping www.baidu.com Ping:unknown Host Www.baidu.com [[email protected]~]# Ping www.baidu.com Ping:unknown Host Www.baidu.com [[email protected]~]# Ping 119.75.218.70 PING 119.75.218.70 (119.75.218.70) bytes of data. Bytes from 119.75.218.70:icmp_seq=1 ttl=128 time=10.6 ms Bytes from 119.75.218.70:icmp_seq=2 ttl=128 time=5.69 ms Bytes from 119.75.218.70:icmp_seq=3 ttl=128 time=5.39 ms Bytes from 119.75.218.70:icmp_seq=4 ttl=128 time=13.2 ms Bytes from 119.75.218.70:icmp_seq=5 ttl=128 time=7.67 ms Bytes from 119.75.218.70:icmp_seq=6 ttl=128 time=9.23 ms Bytes from 119.75.218.70:icmp_seq=7 ttl=128 time=34.4 ms Bytes from 119.75.218.70:icmp_seq=8 ttl=128 time=12.0 ms ^c ---119.75.218.70 ping statistics--- 8 Packets transmitted, 8 received, 0% packet loss, time 7382ms RTT Min/avg/max/mdev = 5.395/12.299/34.452/8.780 ms

Fault resolution:

Setup starts the configuration of the NIC on the GUI and reconfigure the IP address;

The configuration file after the configuration is successful is as follows:

[[email protected]network-scripts]# Cat Ifcfg-eth0 Device=eth0 Type=ethernet Onboot=yes Nm_controlled=yes Bootproto=none ipaddr=192.168.116.140 netmask=255.255.255.0 gateway=192.168.116.2 dns1=192.168.116.2 hwaddr=00:0c:29:5c:fe:67 Ipv6init=no Userctl=no [[email protected]network-scripts]# Cat Ifcfg-eth1 Device=eth1 Type=ethernet Onboot=yes Nm_controlled=yes Bootproto=none Ipv6init=no Userctl=no hwaddr=00:0c:29:5c:fe:71 ipaddr=192.168.142.140 netmask=255.255.255.0 [[email protected]network-scripts]#

Test:

[[email protected]network-scripts]# Ping www.baidu.com PING www.baidu.com (119.75.217.109) bytes of data. Bytes from 119.75.217.109:icmp_seq=1 ttl=128 time=456 ms Bytes from 119.75.217.109:icmp_seq=2 ttl=128 time=336 ms Bytes from 119.75.217.109:icmp_seq=3 ttl=128 time=1280 ms Bytes from 119.75.217.109:icmp_seq=4 ttl=128 time=336 ms Bytes from 119.75.217.109:icmp_seq=5 ttl=128 time=402 ms ^c ---www.baidu.com ping statistics--- 5 Packets transmitted, 5 received, 0% packet loss, time 5380ms RTT Min/avg/max/mdev = 336.635/562.425/1280.376/361.756 ms, pipe 2

Thank you Li Xiang.

Troubleshooting ideas:

Unknown host www.baidu.com is a DNS problem, ping gateway can pingt,ping Baidu IP can also ping through. Determine the DNS issue;

Modify configuration file Ifcfg-eth0, DNS configuration file, Setup reconfigure NIC

Related principle: DNS principle

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Dual-NIC virtual machine does not have Internet access problem: Unknown host www.baidu.com