在ensp中，内网能够访问外网，外网却无法访问内网。
拓扑图如下：
r4 g0/0/2配置
ip address 202.202.202.2 255.255.255.0
nat server protocol tcp global current-interface ftp inside 192.168.12.4 ftp
nat server protocol tcp global current-interface www inside 192.168.12.4 www
nat server protocol tcp global current-interface domain inside 192.168.12.4 domain
nat outbound 2000
acl2000配置
Basic ACL 2000, 1 rule
Acl's step is 5
rule 5 permit source 192.168.0.0 0.0.255.255
nat alg全部打开了
想要实现外网访问内网，实现ftp服务怎么解决呢？
