VPP静态映射实现DNAT

接口基本配置：

DBGvpp# set interface state port7 up
DBGvpp# set interface state port8 up
DBGvpp# set interface ip address port7 50.1.1.1/24
DBGvpp# set interface ip address port8 192.168.1.203/24

网络拓扑：

|-----------|         |------------|           |---------------|
| 50.1.1.2  |---------|    vpp     |------|----| 192.168.1.103 |
|-----------|         |------------|      |    |---------------|
   Host-A           port7        port8    |         Host-B
                                          |
                                          |    |---------------|
                                          |----| 192.168.1.114 |
                                               |---------------|
                                                Host-C(FTP-Server)

启用NAT44配置：

DBGvpp# nat44 enable 

如下192.168.1.203为接口port8的真实IP地址，执行DNAT。配置与以上的SNAT一致，都是使用VPP的静态地址映射。

# nat44 add address 192.168.1.203
# set interface nat44 in port7 out port8
# nat44 add static mapping local 50.1.1.2 external 192.168.1.203
#
# show nat44 static mappings
NAT44 static mappings:
 local 50.1.1.2 external 192.168.1.203 vrf 0
#
# show nat44 interfaces
NAT44 interfaces:
 port8 out
#
# show nat44 addresses
NAT44 pool addresses:
192.168.1.203
  tenant VRF independent

执行192.168.1.103 -> ping -> 192.168.1.203:

1. 在主机50.1.1.2抓包，可见报文： 192.168.1.103->50.1.1.2，执行了目的地址的替换。
   2）在主机192.168.1.103抓包，可见报文： 192.168.1.203->192.168.1.103，执行了源地址的替换。

如下NAT会话所示：

# show nat44 sessions
NAT44 ED sessions:
-------- thread 0 vpp_main: 2 sessions --------
    i2o 50.1.1.2 proto ICMP port 41039 fib 0
    o2i 192.168.1.203 proto ICMP port 41039 fib 0
       external host 192.168.1.103:0
       i2o flow: match: saddr 50.1.1.2 sport 41039 daddr 192.168.1.103 dport 41039 proto ICMP fib_idx 0 rewrite: saddr 192.168.1.203 icmp-id 41039
       o2i flow: match: saddr 192.168.1.103 sport 41039 daddr 192.168.1.203 dport 41039 proto ICMP fib_idx 0 rewrite: daddr 50.1.1.2 icmp-id 41039 txfib 0
       index 0
       last heard 254.15
       total pkts 5, total bytes 420
       static translation