PIX/ASA 7.x/FWSM 3.x：使用静态策略 NAT 将多个全局 IP 地址转换为单个本地 IP 地址

简介

本文档提供了一个示例配置，在 PIX/自适应安全设备 (ASA) 7.x 软件中通过基于策略的静态网络地址转换 (NAT) 将一个本地 IP 地址映射到两个或更多全局 IP 地址。

先决条件

要求

在尝试进行此配置之前，请确保满足以下要求：

• 确保您熟悉 PIX/ASA 7.x CLI 并且以前配置过访问列表和静态 NAT。

使用的组件

本文档中的信息基于以下软件和硬件版本：

• 这一特定示例使用 ASA 5520。但是，策略 NAT 配置适用于所有运行 7.x 的 PIX 或 ASA 设备。

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您使用的是真实网络，请确保您已经了解所有命令的潜在影响。

规则

有关文档规则的详细信息，请参阅 Cisco 技术提示规则。

配置

本配置示例中有一个内部 Web 服务器，它位于 ASA 之后，地址为 192.168.100.50。要求是：服务器需要通过其内部 IP 地址 192.168.100.50 和外部地址 172.16.171.125 访问外部网络接口。还有一项安全策略要求：专用 IP 地址 192.168.100.50 只能通过 172.16.171.0/24 网络访问。另外，互联网控制消息协议(ICMP)和端口80流量是唯一的协议允许入站到内部网络服务器。因为有两个全局 IP 地址映射到一个本地 IP 地址，所以您需要使用策略 NAT。否则， PIX/ASA 会因重迭地址错误拒绝两个一对一的静态映射。

注意： 使用命令查找工具（仅限注册用户）可获取有关本部分所使用命令的详细信息。

网络图

本文档使用以下网络设置

配置

本文档使用以下配置。

ciscoasa(config)#show run
: Saved
:
ASA Version 7.2(2)
!
hostname ciscoasa
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface GigabitEthernet0/0
 nameif outside
 security-level 0
 ip address 172.16.171.124 255.255.255.0
!
interface GigabitEthernet0/1
 nameif inside
 security-level 100
 ip address 192.168.100.1 255.255.255.0
!
interface GigabitEthernet0/2
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet0/3
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Management0/0
 nameif management
 security-level 100
 ip address 192.168.1.1 255.255.255.0
 management-only
!
passwd 2KFQnbNIdI.2KYOU encrypted
ftp mode passive



!--- policy_nat_web1 and policy_nat_web2 are two access-lists that match the source !--- address we want to translate on. Two access-lists are required, though they !--- can be exactly the same.


access-list policy_nat_web1 extended permit ip host 192.168.100.50 any
access-list policy_nat_web2 extended permit ip host 192.168.100.50 any


!--- The inbound_outside access-list defines the security policy, as previously described. !--- This access-list is applied inbound to the outside interface.


access-list inbound_outside extended permit tcp 172.16.171.0 255.255.255.0 
   host 192.168.100.50 eq www
access-list inbound_outside extended permit icmp 172.16.171.0 255.255.255.0 
   host 192.168.100.50 echo-reply
access-list inbound_outside extended permit icmp 172.16.171.0 255.255.255.0 
   host 192.168.100.50 echo
access-list inbound_outside extended permit tcp any host 172.16.171.125 eq www
access-list inbound_outside extended permit icmp any host 172.16.171.125 echo-reply
access-list inbound_outside extended permit icmp any host 172.16.171.125 echo
pager lines 24
logging asdm informational
mtu management 1500
mtu inside 1500
mtu outside 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
no asdm history enable
arp timeout 14400


!--- This first static allows users to reach the translated global IP address of the !--- web server. Since this static appears first in the configuration, for connections !--- initiated outbound from the internal web server, the ASA translates the source !--- address to 172.16.171.125.


static (inside,outside) 172.16.171.125  access-list policy_nat_web1


!--- The second static allows networks to access the web server by its private !--- IP address of 192.168.100.50.



static (inside,outside) 192.168.100.50  access-list policy_nat_web2


!--- Apply the inbound_outside access-list to the outside interface.


access-group inbound_outside in interface outside

route outside 0.0.0.0 0.0.0.0 172.16.171.1 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout uauth 0:05:00 absolute
http server enable
http 192.168.1.0 255.255.255.0 management
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
telnet timeout 5
ssh timeout 5
console timeout 0
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map type inspect dns preset_dns_map
 parameters
  message-length maximum 512
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect rsh
  inspect rtsp
  inspect esmtp
  inspect sqlnet
  inspect skinny
  inspect sunrpc
  inspect xdmcp
  inspect sip
  inspect netbios
  inspect tftp
!
service-policy global_policy global
prompt hostname context

验证

本部分提供的信息可帮助您确认您的配置是否可正常运行。

命令输出解释程序（仅限注册用户）(OIT) 支持某些 show 命令。使用 OIT 可查看对 show 命令输出的分析。

1. 在上游 IOS® 路由器 172.16.171.1 上，请通过 ping 命令验证您是否能够访问 Web 服务器的两个全局 IP 地址。

   router#ping 172.16.171.125
   
   Type escape sequence to abort.
   Sending 5, 100-byte ICMP Echos to 172.16.171.125, timeout is 2 seconds:
   !!!!!
   Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
   router#ping 192.168.100.50
   
   Type escape sequence to abort.
   Sending 5, 100-byte ICMP Echos to 192.168.100.50, timeout is 2 seconds:
   !!!!!
   Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

2. 在 ASA 在，请验证您是否看到在转换 (xlate) 表里建立的转换。

   ciscoasa(config)#show xlate global 192.168.100.50
   2 in use, 28 most used
   Global 192.168.100.50 Local 192.168.100.50
   ciscoasa(config)#show xlate global 172.16.171.125
   2 in use, 28 most used
   Global 172.16.171.125 Local 192.168.100.50
   

故障排除

本部分提供的信息可用于对配置进行故障排除。

如果 ping 命令或连接失败，请尝试使用 syslog 确定转换配置是否有问题。在负荷很轻的网络（例如实验室环境）中，日志缓冲区大小通常足以满足排除故障的需要。否则，您需要将 syslog 发送到外部 syslog 服务器中。在第 6 级对缓冲区启用日志记录以便在这些 syslog 条目中查看配置是否正确。

ciscoasa(config)#logging buffered 6
ciscoasa(config)#logging on


!--- From 172.16.171.120, initiate a TCP connection to port 80 to both the external !--- (172.16.171.125) and internal addresses (192.168.100.50).


ciscoasa(config)#show log
Syslog logging: enabled
    Facility: 20
    Timestamp logging: disabled
    Standby logging: disabled
    Deny Conn when Queue Full: disabled
    Console logging: disabled
    Monitor logging: disabled
    Buffer logging: level debugging, 4223 messages logged
    Trap logging: disabled
    History logging: disabled
    Device ID: disabled
    Mail logging: disabled
    ASDM logging: level informational, 4032 messages logged
%ASA-5-111008: User 'enable_15' executed the 'clear logging buffer' command.
%ASA-7-609001: Built local-host outside:172.16.171.120
%ASA-7-609001: Built local-host inside:192.168.100.50
%ASA-6-302013: Built inbound TCP connection 67 for outside:172.16.171.120/33687 
(172.16.171.120/33687) to inside:192.168.100.50/80 (172.16.171.125/80)
%ASA-6-302013: Built inbound TCP connection 72 for outside:172.16.171.120/33689 
(172.16.171.120/33689) to inside:192.168.100.50/80 (192.168.100.50/80)

如果在日志中看到转换错误，请仔细检查您的 NAT 配置。如果未看到任何系统日志，请使用 ASA 中的捕获功能尝试捕获接口上的数据流。为了设置捕获，您必须首先指定一个访问列表以匹配特定类型的数据流或 TCP 流。接下来，您必须将此捕获应用到一个或多个接口以便开始捕获数据包。

!--- Create a capture access-list to match on port 80 traffic to !--- the external IP address of 172.16.171.125. !--- Note: These commands are over two lines due to spatial reasons. 


ciscoasa(config)#access-list acl_capout permit tcp host 172.16.171.120 
     host 172.16.171.125 eq 80
ciscoasa(config)#access-list acl_capout permit tcp host 172.16.171.125 
    eq 80 host 172.16.171.120
ciscoasa(config)#


!--- Apply the capture to the outside interface.
 

ciscoasa(config)#capture capout access-list acl_capout interface outside


!--- After you initiate the traffic, you see output similar to this when you view !--- the capture. Note that packet 1 is the SYN packet from the client, while packet !--- 2 is the SYN-ACK reply packet from the internal server. If you apply a capture !--- on the inside interface, in packet 2 you should see the server reply with !--- 192.168.100.50 as its source address. 

ciscoasa(config)#show capture capout
4 packets captured
   1: 13:17:59.157859 172.16.171.120.21505 > 172.16.171.125.80: S 
      2696120951:2696120951(0) win 4128 <mss 1460>
   2: 13:17:59.159446 172.16.171.125.80 > 172.16.171.120.21505: S 
      1512093091:1512093091(0) ack 2696120952 win 4128 <mss 536>
   3: 13:17:59.159629 172.16.171.120.21505 > 172.16.171.125.80: . 
      ack 1512093092 win 4128
   4: 13:17:59.159873 172.16.171.120.21505 > 172.16.171.125.80: .
      ack 1512093092 win 4128

相关信息

• ASA 7.2 命令参考
• Cisco PIX 防火墙软件
• Cisco Secure PIX 防火墙命令参考
• 安全产品 Field Notices（包括 PIX）
• 请求注解 (RFC)
• 技术支持和文档 - Cisco Systems