linux kvm 虚拟机 nat 网络 iptables 宿主机端口转发到虚拟机

我安装了kvm，并使用vmbuilder在服务器上设置了多个guest虚拟机。这是以下配置：

server host1 (xxx.xxx.xxx.xxx) ->  guest vm1 (192.168.122.203)
                               ->  guest vm2 (192.168.122.204)

其中xxx.xxx.xxx.xxx是host1的固定IP地址。

我想使用以下命令连接到vm1：

ssh username@host1 -p 2222

我试图通过在iptables中添加以下规则来做到这一点：

sudo iptables --table nat --append PREROUTING --protocol tcp --destination xxx.xxx.xxx.xxx --destination-port 2222 --jump DNAT --to-destination 192.168.122.203:22

但是我运行时出现超时：

ssh username@host1 -p 2222

这是我的iptables规则：

sudo iptables -nL -v --line-numbers -t nat
Chain PREROUTING (policy ACCEPT 32446 packets, 3695K bytes)
num   pkts bytes target     prot opt in     out     source               destination         
1        7   420 DNAT       tcp  --  *      *       0.0.0.0/0            xxx.xxx.xxx.xxx        tcp dpt:2222 to:192.168.122.203:22

Chain INPUT (policy ACCEPT 8961 packets, 968K bytes)
num   pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 350 packets, 23485 bytes)
num   pkts bytes target     prot opt in     out     source               destination         

Chain POSTROUTING (policy ACCEPT 357 packets, 23905 bytes)
num   pkts bytes target     prot opt in     out     source               destination         
1      151  9060 MASQUERADE  tcp  --  *      *       192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
2       99  7524 MASQUERADE  udp  --  *      *       192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
3        3   252 MASQUERADE  all  --  *      *       192.168.122.0/24    !192.168.122.0/24



sudo iptables -nL -v --line-numbers 
Chain INPUT (policy ACCEPT 14 packets, 1147 bytes)
num   pkts bytes target     prot opt in     out     source               destination         
1      454 30229 ACCEPT     udp  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:53
2        0     0 ACCEPT     tcp  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:53
3        0     0 ACCEPT     udp  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:67
4        0     0 ACCEPT     tcp  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:67

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num   pkts bytes target     prot opt in     out     source               destination         
1     589K 2304M ACCEPT     all  --  *      virbr0  0.0.0.0/0            192.168.122.0/24     state RELATED,ESTABLISHED
2     403K   24M ACCEPT     all  --  virbr0 *       192.168.122.0/24     0.0.0.0/0           
3        0     0 ACCEPT     all  --  virbr0 virbr0  0.0.0.0/0            0.0.0.0/0           
4        1    60 REJECT     all  --  *      virbr0  0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable
5        0     0 REJECT     all  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable

Chain OUTPUT (policy ACCEPT 4 packets, 480 bytes)

解决啦

我在nat表中添加了这2条规则：

$sudo iptables -t nat -A PREROUTING -p tcp --dport 2222 -j DNAT --to-destination 192.168.122.203:22
$sudo iptables -t nat -A POSTROUTING -p tcp --dport 22 -d 192.168.122.203 -j SNAT --to 192.168.122.1

然后我删除了表格过滤器FORWARD链的规则4和5

$sudo iptables -nL -v --line-numbers -t filter

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
(...)        
4        7   420 REJECT     all  --  *      virbr0  0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable
5        0     0 REJECT     all  --  virbr0 *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable

$sudo iptables -D FORWARD 5 -t filter
$sudo iptables -D FORWARD 4 -t filter

现在，我通过执行以下操作连接到vm1：

$ssh user1@host -p 2222
user1@vm1:~$