Cisco ASA 实现 IPSec 虚拟专用网（内附故障排查）

传送门：Cisco 路由器配置实例： https://www.geek-share.com/detail/2784042124.html
其实，防火墙和路由器的配置非常相似，可以参考上方传送门，下方会介绍一个防火墙的配置实例
一、路由器的故障诊断排查
1、show crypto isakmp sa

R1:show crypto isakmp sa               # 可以显示数据连接sa的细节信息

MM_NO_STATE ：ISAKMP SA建立的初始状态；管理连接建立失败也会处于该状态
MM_SA_SETUP ：对等体之间ISAKMP策略协商成功后处于该状态
MM_KEY_EXCH ：对等体通过DH算法成功建立共享密钥，此时还没有进行设备验证
MM_KEY_AUTH ：对等体成功进行设备验证，之后会过渡到QM_IDLE状态
QM_IDLE ：管理连接成功建立，即将过渡到阶段2的数据连接建立过程

2、debug crypto isakmp

R1：debug crypto isakmp                # 诊断和排查管理连接出现的问题

故障实例一：两端加密算法不匹配

ISAKMP:(0:0:N/A:0):Checking ISAKMP transform 1 against priority 1 policy
ISAKMP:      default group 1
ISAKMP:      encryption DES-CBC
ISAKMP:      hash SHA
ISAKMP:      auth pre-share
ISAKMP:      life type in seconds
ISAKMP:      life duration (VPI) of  0x0 0x1 0x51 0x80
ISAKMP:(0:0:N/A:0):Encryption algorithm offered does not match policy!                        # 加密算法不匹配
ISAKMP:(0:0:N/A:0):atts are not acceptable. Next payload is 0
……                            # 策略不被接受
ISAKMP:(0:0:N/A:0):no offers accepted!                  # 没有匹配策略
……
received packet from 10.0.0.1 dport 500 sport 500 Global (R) MM_NO_STATE                           # 策略进入未成功状态

故障案例二：两端使用的预共享密钥不一致

ISAKMP:(0:0:N/A:0):Checking ISAKMP transform 1 against priority 1 policy
ISAKMP:      default group 1
ISAKMP:      encryption DES-CBC
ISAKMP:      hash SHA
ISAKMP:      auth pre-share
ISAKMP:      life type in seconds
ISAKMP:      life duration (VPI) of  0x0 0x1 0x51 0x80
ISAKMP:(0:0:N/A:0):atts are acceptable. Next payload is 0
……            # 算法已匹配，开始秘钥交换及身份验证
ISAKMP (0:134217729): received packet from 10.0.0.1 dport 500 sport 500 Global (R) MM_KEY_EXCH
ISAKMP: reserved not zero on ID payload!
%CRYPTO-4-IKMP_BAD_MESSAGE: IKE message from 10.0.0.1     failed its sanity check or is malformed
# 完整性验证失败，将停留在MM     KEY    EXCH 阶段

二、防火墙和路由器的区别：
IKE 协商：
路由默认开启
ASA 防火墙默认关闭，必须手动开启，如下：

ASA（config）# crypto  isakmp  enable  outside

隧道组特性的引入：
防火墙从6.x版本升级到7.0版本引入的新特性
主要用于简化IPSec会话的配置和管理
三、开始配置
环境如下：

需求如下：
lan1区域和lan2区域互通
lan1区域和lan3区域互通
lan2区域和lan3区域互通（lan2→lan1→lan3）
所有区域能够访问中间ISP
配前须知（不好意思，我这里以路由器代替了pc机所以验证有点简略）：

1. 自行配置接口IP之类
2. 这里我是使用了路由器充当PC机所以需要在路由器上配置个默认路由充当网关
3. 防火墙往外配置一条默认路由

R1配置（R3、R4配置类似）：

R1#conf t
R1(config)#int f 0/0
R1(config-if)#ip add 192.168.1.10 255.255.255.0                # 配置接口IP
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.1                   # 默认路由充当网关

R2配置如下（ISP不需要配置路由）：

R2#conf t
R2(config)#int f 0/1
R2(config-if)#ip add 201.0.0.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#int f 0/1
R2(config-if)#ip add 202.0.0.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#int f 1/0
R2(config-if)#ip add 202.0.0.1 255.255.255.0
R2(config-if)#no shutdown

1、配置
ASA1（lan1→lan2）配置如下

ciscoasa> en
Password:
ciscoasa# conf t
ciscoasa(config)# int e 0/0
ciscoasa(config-if)# nameif inside                    # 配置为内接口
ciscoasa(config-if)# ip add 192.168.1.1
ciscoasa(config-if)# no shutdown
ciscoasa(config-if)# exit
ciscoasa(config)# int e 0/1
ciscoasa(config-if)# nameif outside                  # 配置为外接口
ciscoasa(config-if)# ip add 201.0.0.2
ciscoasa(config-if)# no shutdown
ciscoasa(config)# route outside 0 0 201.0.0.2                   # 配置到外部的默认路由，这里的0相当于0.0.0.0
ciscoasa(config)# crypto isakmp enable outside                 # 开启IKE协商功能
ciscoasa(config)# crypto isakmp policy 1                            # 配置管理连接
ciscoasa(config-isakmp-policy)# encryption aes                 # 加密为aes
ciscoasa(config-isakmp-policy)# hash md5                         # 认证为 md5
ciscoasa(config-isakmp-policy)# group 2
ciscoasa(config-isakmp-policy)# authentication pre-share      # 预先设置共享秘钥
ciscoasa(config-isakmp-policy)# lifetime 10000
ciscoasa(config-isakmp-policy)# exit
ciscoasa(config)# crypto isakmp key 123.com address 202.0.0.2               # 设置共享秘钥
# 防火墙中有两种配置，一会在ASA2中使用
ciscoasa(config)# access-list lan1_lan2 permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0                    # 编写1.0到2.0的ACL
ciscoasa(config)# crypto ipsec transform-set test-set esp-aes esp-md5-hmac           # 此四条配置数据连接
ciscoasa(config)# crypto map test-map 1 match address lan1_lan2
ciscoasa(config)# crypto map test-map 1 set peer 202.0.0.1
ciscoasa(config)# crypto map test-map 1 set transform-set  test-set
ciscoasa(config)# crypto map test-map interface outside          # 应用到外部的逻辑接口上

ASA2配置如下

ciscoasa> en
Password:
ciscoasa# conf t
ciscoasa(config)# int e 0/0                          # 这里我就不介绍配置含义了，和上面基本相似
ciscoasa(config-if)# nameif outside
ciscoasa(config-if)# ip add 202.0.0.2
ciscoasa(config-if)# no shutdown
ciscoasa(config-if)# exit
ciscoasa(config)# int e 0/1
ciscoasa(config-if)# nameif inside
ciscoasa(config-if)# ip add 192.168.2.1
ciscoasa(config-if)# no shutdown
ciscoasa(config-if)# exit
ciscoasa(config)# route outside 0 0 202.0.0.1
ciscoasa(config)# crypto isakmp enable outside
ciscoasa(config)# crypto isakmp policy 1
ciscoasa(config-isakmp-policy)# encryption aes
ciscoasa(config-isakmp-policy)# hash md5
ciscoasa(config-isakmp-policy)# group 2
ciscoasa(config-isakmp-policy)# authentication pre-share
ciscoasa(config-isakmp-policy)# lifetime 10000
ciscoasa(config)# tunnel-group 201.0.0.2 type ipsec-l2l             # 另一种配置秘钥方式
ciscoasa(config)# tunnel-group 201.0.0.2 ipsec-attributes
ciscoasa(config-tunnel-ipsec)# pre-shared-key 123.com
ciscoasa(config-tunnel-ipsec)# exit
ciscoasa(config)# access-list lan2_lan1 permit ip 192.168.2.0 255.255.255.0 192.168.1.0 255.255.255.0
ciscoasa(config)# crypto ipsec transform-set test-set esp-aes esp-md5-hmac
ciscoasa(config)# crypto map test-map 1 match address lan2_lan1
ciscoasa(config)# crypto map test-map 1 set peer 201.0.0.2
ciscoasa(config)# crypto map test-map 1 set transform-set test-set
ciscoasa(config)# crypto map test-map interface outside
R1#ping 192.168.2.10

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.2.10, timeout is 2 seconds:
!!!!!

ASA1（lan1→lan3）配置如下

# 在ASA之前配置过到lan2区域，所以可以以上面为基础接着配置
ciscoasa(config)# tunnel-group 203.0.0.2 type ipsec-l2l
ciscoasa(config)# tunnel-group 203.0.0.2 ipsec-attributes
ciscoasa(config-tunnel-ipsec)# pre-shared-key 123.com
ciscoasa(config)# access-list lan1_lan3 permit ip 192.168.1.0 255.255.255.0 192.168.3.0  255.255.255.0
ciscoasa(config)# crypto map test-map 2 match address lan1_lan3
WARNING: The crypto map entry is incomplete!              # 这里出现的警告是正常的
ciscoasa(config)# crypto map test-map 2 set peer 203.0.0.2
WARNING: The crypto map entry is incomplete!
ciscoasa(config)# crypto map test-map 2 set transform-set test-set

ASA3配置如下（和ASA2配置基本详细）

ciscoasa> en
Password:
ciscoasa# conf t
ciscoasa(config)# int e 0/0
ciscoasa(config-if)# nameif outside
ciscoasa(config-if)# ip add 203.0.0.2
ciscoasa(config-if)# no shutdown
ciscoasa(config-if)# exit
ciscoasa(config)# int e 0/1
ciscoasa(config-if)# nameif inside
ciscoasa(config-if)# ip add 192.168.3.1
ciscoasa(config-if)# no shutdown
ciscoasa(config)# route outside 0 0 203.0.0.1
ciscoasa(config)# crypto isakmp enable outside
ciscoasa(config)# crypto isakmp policy 1
ciscoasa(config-isakmp-policy)# authentication pre-share
ciscoasa(config-isakmp-policy)# encryption aes
ciscoasa(config-isakmp-policy)# hash md5
ciscoasa(config-isakmp-policy)# group 2
ciscoasa(config-isakmp-policy)# lifetime 10000
ciscoasa(config-isakmp-policy)# exit
ciscoasa(config)# crypto isakmp key 123.com address 201.0.0.2
ciscoasa(config)# access-list lan3_lan1 permit ip 192.168.3.0 255.255.255.0 192.168.1.0 255.255.255.0
ciscoasa(config)# crypto ipsec transform-set test-set esp-aes esp-md5-hmac
ciscoasa(config)# crypto map test-map 1 match address lan3_lan1
ciscoasa(config)# crypto map test-map 1 set peer 201.0.0.2
ciscoasa(config)# crypto map test-map 1 set transform-set test-set
ciscoasa(config)# crypto map test-map interface outside
R4#ping 192.168.1.10

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.10, timeout is 2 seconds:
!!!!!

2、实现lan2→lan3通信：
ASA1配置如下

ciscoasa(config)# same-security-traffic permit intra-interface         # 允许流量进入和离开同一个接口
ciscoasa(config)# access-list lan1_lan2 permit ip 192.168.3.0 255.255.255.0 192.168.2.0 255.255.255.0
ciscoasa(config)# access-list lan1_lan3 permit ip 192.168.2.0 255.255.255.0 192.168.3.0 255.255.255.0

ASA2配置如下

ciscoasa(config)# access-list lan2_lan1 permit ip 192.168.2.0 255.255.255.0 192.168.3.0 255.255.255.0

ASA3配置如下

ciscoasa(config)# access-list lna3_lan1 permit ip 192.168.3.0 255.255.255.0 192.168.2.0 255.255.255.0
R3#ping 192.168.3.10

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.3.10, timeout is 2 seconds:
!!!!!

3、访问ISP
如果需要让内网能访问互联网，需要在ASA上做PAT，并启用nat控制，豁免***的流量

ASA1配置如下

ciscoasa(config)# nat-control           # 启用nat控制
ciscoasa(config)# nat (inside) 1 0 0            # 配置pat
ciscoasa(config)# global (outside) 1 interface                # 映射到接口
# 不使用原来的ACL条目，因为有lan1_lan2和lan1_lan3,无法同时豁免两个，所以重新定义ACL
ciscoasa(config)# access-list aaa permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0
ciscoasa(config)# access-list aaa permit ip 192.168.1.0 255.255.255.0 192.168.3.0 255.255.255.0
ciscoasa(config)# nat (inside) 0 access-list aaa                # 应用到接口

ASA2配置如下

ciscoasa(config)# nat (inside) 1 0 0
ciscoasa(config)# global (outside) 1 interface
ciscoasa(config)# nat (inside) 0 access-list lan2_lan1

ASA3配置如下

ciscoasa(config)# nat (inside) 1 0 0
ciscoasa(config)# global (outside) 1 interface
ciscoasa(config)# nat (inside) 0 access-list lan3_lan1