【KVM虚拟化】· KVM中的网络

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🦐专栏地址：KVM虚拟化专栏

虚拟机的网络模式

基于NAT（Network Address Translation）的虚拟网络

基于网桥（Bridge）的虚拟网络

用户自定义的隔离的虚拟网络

直接分配网络设备（包括VT-d和SR-IOV）

网络配置文件

下面是默认网络配置文件，地址是122网段，默认的网络为NAT模式。

[root@kvmserver ~]# cat /etc/libvirt/qemu/networks/default.xml 
<!--
WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
OVERWRITTEN AND LOST. Changes to this xml configuration should be made using:
  virsh net-edit default
or other application using the libvirt API.
-->
​
<network>
  <name>default</name>
  <uuid>d01fdb52-9f49-4e03-a2d4-fd6382f11396</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:fb:02:fe'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254'/>
    </dhcp>
  </ip>
</network>

virsh查看命令

[root@kvmserver ~]# virsh net-list
 Name                 State      Autostart     Persistent
----------------------------------------------------------
 default              active     yes           yes
​
[root@kvmserver ~]# virsh net-info default
Name:           default
UUID:           d01fdb52-9f49-4e03-a2d4-fd6382f11396
Active:         yes
Persistent:     yes
Autostart:      yes
Bridge:         virbr0
​
[root@kvmserver ~]# virsh net-dumpxml default 
<network connections='2'>
  <name>default</name>
  <uuid>d01fdb52-9f49-4e03-a2d4-fd6382f11396</uuid>
  <forward mode='nat'>
    <nat>
      <port start='1024' end='65535'/>
    </nat>
  </forward>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:fb:02:fe'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254'/>
    </dhcp>
  </ip>
</network>

基于NAT的虚拟网络

默认宿主机会有一个虚拟网卡virbr0,其实是一个虚拟交换机，默认模式就不在详细介绍了。

[root@kvmserver ~]# ifconfig virbr0
virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:fb:02:fe  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

基于网桥的虚拟网络

首先需要创建虚拟交换机，可以使用virt-manager来创建，也可以修改网络配置文件。

[root@kvmserver ~]# cd /etc/sysconfig/network-scripts/
[root@kvmserver network-scripts]# cp ifcfg-ens33 ifcfg-br10
[root@kvmserver network-scripts]# vim ifcfg-br10
DEVICE=br10
TYPE=Bridge
BOOTPROTO=static
NAME=br10
ONBOOT=yes
IPADDR=192.168.8.100
GATEWAY=192.168.8.2
DNS1=8.8.8.8
[root@kvmserver network-scripts]# vim ifcfg-ens33
TYPE=Ethernet
NAME=ens33
DEVICE=ens33
ONBOOT=yes
BRIDGE=br10
[root@kvmserver network-scripts]# systemctl restart network

查看br10是否配置成功。

[root@kvmserver ~]# ip a show br10
11: br10: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:0c:29:bb:33:e4 brd ff:ff:ff:ff:ff:ff
    inet 192.168.8.100/24 brd 192.168.8.255 scope global noprefixroute br10
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:febb:33e4/64 scope link 
       valid_lft forever preferred_lft forever

创建虚拟机测试，首先创建dp1池。

[root@kvmserver ~]# virsh pool-define-as dp1 dir --target /dir
Pool dp1 defined
​
[root@kvmserver ~]# virsh pool-start dp1
Pool dp1 started
​
[root@kvmserver ~]# virsh pool-autostart dp1
Pool dp1 marked as autostarted
​
[root@kvmserver ~]# virsh pool-list --all
 Name                 State      Autostart 
-------------------------------------------
 dirpool              active     yes       
 dp1                  active     yes       
 img                  active     yes       
 iso                  active     yes       
 nfspool              active     yes       
 test                 active     yes       
 vgpool               active     yes 

创建在dp1池创建磁盘文件，名称为vol1.qcow2。

[root@kvmserver ~]# virsh vol-create-as dp1 vol1.qcow2 8G --format qcow2
Vol vol1.qcow2 created
​
[root@kvmserver ~]# virsh vol-list dp1
 Name                 Path                                    
------------------------------------------------------------------------------
 vol1.qcow2           /dir/vol1.qcow2 

安装虚拟机测试网络，桥接模式的网络应是可以访问外网，而外网也可以访问虚拟机。这里要记得不是一定要重新安装，可以使用attach-interface命令给已有虚拟机添加网络。

[root@kvmserver ~]# virt-install -n vm001 -r 1024 --vcpus 1 -l /kvm/iso/centos.iso --disk /dir/vol1.qcow2 -w bridge=br10 --nographics -x "console=ttyS0"

经过安装等待，我们来到了用户登录界面，输入root用户加密码，进入终端。

CentOS Linux 7 (Core)
Kernel 3.10.0-1160.el7.x86_64 on an x86_64

localhost login: root
Password: 

直接使用dhcp获取地址，来测试网络

[root@localhost ~]# dhclient
[root@localhost ~]# ip a show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 52:54:00:14:8f:0b brd ff:ff:ff:ff:ff:ff
    inet 192.168.8.131/24 brd 192.168.8.255 scope global dynamic ens3
       valid_lft 1670sec preferred_lft 1670sec
[root@localhost ~]# ping www.baidu.com -c 4
PING www.a.shifen.com (182.61.200.7) 56(84) bytes of data.
64 bytes from 182.61.200.7 (182.61.200.7): icmp_seq=1 ttl=128 time=34.7 ms
64 bytes from 182.61.200.7 (182.61.200.7): icmp_seq=2 ttl=128 time=45.0 ms
64 bytes from 182.61.200.7 (182.61.200.7): icmp_seq=3 ttl=128 time=75.7 ms
64 bytes from 182.61.200.7 (182.61.200.7): icmp_seq=4 ttl=128 time=81.2 ms

--- www.a.shifen.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3027ms
rtt min/avg/max/mdev = 34.754/59.204/81.264/19.735 ms

打开windows终端，ping虚拟机成功的话，双向通信完成。未成功则检查网络信息。

基于隔离的虚拟网络

查看虚拟机网络配置文件都有哪些

[root@kvmserver ~]# cd /etc/libvirt/qemu/networks/
[root@kvmserver networks]# ls
autostart  default.xml

创建一个用户定义的隔离网络配置文件

[root@kvmserver networks]# vim dir.xml

<network>
  <name>dir</name>
  <uuid>7b0b9f14-ff50-4f8f-ac0f-9adcc4714441</uuid>
  <bridge name='virbr1' stp='on' delay='0'/>
  <mac address='52:54:00:65:0e:f9'/>
  <domain name='dir'/>
  <ip address='192.168.100.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.100.128' end='192.168.100.254'/>
    </dhcp>
  </ip>
</network>

把网络加入域并查看

[root@kvmserver networks]# virsh net-define dir.xml 
Network dir defined from dir.xml
​
[root@kvmserver networks]# virsh net-start dir
Network dir started
​
[root@kvmserver networks]# virsh net-autostart dir
Network dir marked as autostarted
​
[root@kvmserver networks]# virsh net-list --all
 Name                 State      Autostart     Persistent
----------------------------------------------------------
 default              active     yes           yes
 dir                  active     yes           yes

在dp1池中创建磁盘文件

[root@kvmserver networks]# virsh vol-create-as dp1 vol2.qcow2 8G --format qcow2
Vol vol2.qcow2 created
​
[root@kvmserver networks]# virsh vol-list dp1
 Name                 Path                                    
------------------------------------------------------------------------------
 vol1.qcow2           /dir/vol1.qcow2                         
 vol2.qcow2           /dir/vol2.qcow2 

创建虚拟机，在创建好的磁盘文件中创建vm002虚拟机，网络状态指定dir（dir是上面配置的配置文件dir.xml）等待配置测试即可。

[root@kvmserver networks]# virt-install -n vm002 -r 1024 --vcpus 1 -l /kvm/iso/centos.iso --disk /dir/vol2.qcow2 -w network=dir --nographics -x "console=ttyS0"

测试结果应为完全独立的网络，上不了外网，而外网也无法访问内网。