KVM Nic Mode (nat/usernetworking)

By default, if you do not specify any network mode, KVM will silently choose NAT mode for us, in addition to NAT there is bridge and VLAN mode.

User Networking (NAT mode)

With this mode, no additional configuration is required for the host. Under normal circumstances, the virtual machine can access the host's physical network directly, and the host cannot access the virtual machine.

The benefit is simple, no configuration, and if the host can surf the Internet, the virtual machine can also surf the Internet.

The disadvantage is that the network between the virtual machine and the virtual machine is unreachable, the ICMP protocol does not work properly (that is, the ping function does not return a normal value), and NAT uses a forwarding mechanism, so the efficiency is low.

#  Host:  ip address [[email protected] qemuimages]$ ifconfig p3p1p3p1: flags=4163 <UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500         inet 192.168.1.102  netmask 255.255.255.0  broadcast 0.0.0.0         inet6 fe80::ba88:e3ff:fef3:af7c  prefixlen 64   scopeid 0x20<link>        ether b8:88:e3: f3:af:7c  txqueuelen 1000   (Ethernet)          rx packets 232953  bytes 210207598  (200.4&NBSP;MIB)          RX errors 0  dropped 0  overruns 0   frame 0        tx packets 282248  bytes  40669709  (38.7&NBSP;MIB) &Nbsp;       tx errors 0  dropped 0 overruns  0  carrier 0  collisions 0#  host:  can access the internet normally [[email protected ] qemuimages]$ ping ping www.a.shifen.com  (119.75.217.56)  56 (+)  bytes  of data.64 bytes from 119.75.217.56: icmp_seq=1 ttl=56 time=33.8  ms64 bytes from 119.75.217.56: icmp_seq=2 ttl=56 time=31.8 ms #   Host:  boot virtual machine [[email protected] qemuimages]$ sudo qemu-kvm -m 2048  -hda networknode.img

Virtual machines:

Ping www.baidu.com Conclusion: Ping does not pass the Internet

Ping Host (192.168.1.102) Conclusion: Ping not detox host and internet

wget http://www.baidu.com Conclusion: The page can be downloaded normally

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Finally, some advanced features enable host access to virtual machines.

#  host:  The HOSTFWD parameter is provided when the virtual machine is started #  This parameter allows the host to connect to the VM's 22 port via port 60000 without any change in other aspects. [[email protected] qemuimages]$ sudo qemu-kvm -m 2048 -hda  networknode.img -net nic -net user,hostfwd=tcp:127.0.0.1:60000-:22#  host:  Connect to a virtual machine      conclusion:  can connect to the virtual machine normally [[Email protected] qemuimages]$ ssh [email  protected] -p 60000The authenticity of host  ' [localhost]:60000  ([ 127.0.0.1]:60000) '  can ' t be established. rsa key fingerprint is 42:73:36:58:f3:75:12:35:8a:07:8d:4d:32:1a:59:3a. are you sure you want to continue connecting  (yes/no)?  yesWarning : permanently added  ' [localhost]:60000 '   (RSA)  to the list of  Known hosts. [email protected] ' s password: last login: sun nov 30 23:53:27  2014[[emaIl protected] ~]# ifconfig ens3: flags=4163<up,broadcast,running,multicast>   mtu 1500        inet 10.0.2.15   netmask 255.255.255.0  broadcast 0.0.0.0         inet6 fe80::5054:ff:fe12:3456  prefixlen 64  scopeid 0x20<link>         ether 52:54:00:12:34:56  txqueuelen 1000    (Ethernet)         RX packets 66  bytes  8768  (8.5 kib)         RX errors 0   dropped 0  overruns 0  frame 0         TX packets 81  bytes 11168  (10.9 kib)          tx errors&nBsp;0  dropped 0 overruns 0  carrier 0  collisions 0lo:  flags=73<UP,LOOPBACK,RUNNING>  mtu 65536         inet 127.0.0.1  netmask 255.0.0.0         inet6 ::1  prefixlen 128  scopeid 0x10





This article is from the Software testing blog, so be sure to keep this source http://9614554.blog.51cto.com/9604554/1584880
KVM Nic Mode (nat/usernetworking)