1.测试拓扑：
2.基本配置：
R1：
interface FastEthernet0/0
ip address 202.100.1.2 255.255.255.0
no shut
ASA842：
interface GigabitEthernet0
nameif inside
ip address 10.1.1.254 255.255.255.0
no shut
interface GigabitEthernet1
nameif outside
ip address 202.100.1.1 255.255.255.0
no shut
route outside 0.0.0.0 0.0.0.0 202.100.1.2
R2：
interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
no shut
ip route 0.0.0.0 0.0.0.0 10.1.1.254
enable secret cisco
line vty 0 4
password cisco
login
-----R1开启telnet服务
PC1：
IP:10.1.1.2/24
GW:10.1.1.254
3.防火墙NAT配置：
A.动态PAT:
object network insidenet
subnet 10.1.1.0 255.255.255.0
nat (inside,outside) dynamic interface
B.静态PAT:
object network R1
host 10.1.1.1
nat (inside,outside) static interface service tcp 23 2323
4.防火墙策略配置：
A.开启ICMP审查
policy-map global_policy
class inspection_default
inspect icmp
B.允许外面Telnet内网R2
access-list outside-in extended permit tcp any object R1 eq 23
access-group outside-in in interface outside
5.测试：
A.PC1能正常通过R2内网地址telnet R2
B.R1能正常通过R2映射后公网地址telnet R1
R1#telnet 202.100.1.1 2323
Trying 202.100.1.1, 2323 ... Open
User Access Verification
Password:
R2>
C.但是PC2却无法通过R1映射后的公网地telnet R1
D.通过如下链接，修改ASA outside接口掩码为30为，PC1还是不能telnet R2的公网地址，抓包发现ASA发出tcp的syn包时，R1只是给了个ICMP重定向包。
/read.php?tid=228594
E.通过如下链接，配置hairpin NAT
/thread/2121856
①允许相同接口返回流量
same-security-traffic permit intra-interface
②定义对象和服务
object network R1-Public
host 202.100.1.1
object service telnet
service tcp destination eq 23
object service telnet-outside
service tcp destination eq 2323
③配置hairpin NAT
nat (inside,inside) source static any interface destination static R1-Public R1 service telnet-outside telnet
④测试，PC1能通过telnet 202.100.1.1 2323登录R2，登录R2后看到的源地址为防火墙内网口地址
