Cisco ASA 實現 IPSec 虛擬專用網（內附故障排查）

傳送門：Cisco 路由器配置實例： https://blog.51cto.com/14227204/2448319
其實，防火牆和路由器的配置很是類似，能夠參考上方傳送門，下方會介紹一個防火牆的配置實例
1、路由器的故障診斷排查
一、show crypto isakmp sa

R1:show crypto isakmp sa               # 能夠顯示數據鏈接sa的細節信息

MM_NO_STATE ：ISAKMP SA創建的初始狀態；管理鏈接創建失敗也會處於該狀態
MM_SA_SETUP ：對等體之間ISAKMP策略協商成功後處於該狀態
MM_KEY_EXCH ：對等體經過DH算法成功創建共享密鑰，此時尚未進行設備驗證
MM_KEY_AUTH ：對等體成功進行設備驗證，以後會過渡到QM_IDLE狀態
QM_IDLE ：管理鏈接成功創建，即將過渡到階段2的數據鏈接創建過程

二、debug crypto isakmp

R1：debug crypto isakmp                # 診斷和排查管理鏈接出現的問題

故障實例一：兩端加密算法不匹配

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!                  # 沒有匹配策略
……
received packet from 10.0.0.1 dport 500 sport 500 Global (R) MM_NO_STATE                           # 策略進入未成功狀態

故障案例二：兩端使用的預共享密鑰不一致

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，開始祕鑰交換及身份驗證
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          
# 完整性驗證失敗，將停留在MM     KEY    EXCH 階段

2、防火牆和路由器的區別：
IKE 協商：
路由默認開啓
ASA 防火牆默認關閉，必須手動開啓，以下：

ASA（config）# crypto  isakmp  enable  outside

隧道組特性的引入：
防火牆從6.x版本升級到7.0版本引入的新特性
主要用於簡化IPSec會話的配置和管理
3、開始配置
環境以下：

需求以下：
lan1區域和lan2區域互通
lan1區域和lan3區域互通
lan2區域和lan3區域互通（lan2→lan1→lan3）
全部區域可以訪問中間ISP
配前須知（很差意思，我這裏以路由器代替了pc機因此驗證有點簡略）：

1. 自行配置接口IP之類
2. 這裏我是使用了路由器充當PC機因此須要在路由器上配置個默認路由充當網關
3. 防火牆往外配置一條默認路由

R1配置（R三、R4配置相似）：

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                   # 默認路由充當網關

R2配置以下（ISP不須要配置路由）：

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

一、配置
ASA1（lan1→lan2）配置以下

ciscoasa> en
Password:
ciscoasa# conf t
ciscoasa(config)# int e 0/0
ciscoasa(config-if)# nameif inside                    # 配置爲內接口
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                  # 配置爲外接口
ciscoasa(config-if)# ip add 201.0.0.2
ciscoasa(config-if)# no shutdown
ciscoasa(config)# route outside 0 0 201.0.0.2                   # 配置到外部的默認路由，這裏的0至關於0.0.0.0 
ciscoasa(config)# crypto isakmp enable outside                 # 開啓IKE協商功能
ciscoasa(config)# crypto isakmp policy 1                            # 配置管理鏈接
ciscoasa(config-isakmp-policy)# encryption aes                 # 加密爲aes
ciscoasa(config-isakmp-policy)# hash md5                         # 認證爲 md5
ciscoasa(config-isakmp-policy)# group 2
ciscoasa(config-isakmp-policy)# authentication pre-share      # 預先設置共享祕鑰
ciscoasa(config-isakmp-policy)# lifetime 10000         
ciscoasa(config-isakmp-policy)# exit 
ciscoasa(config)# crypto isakmp key 123.com address 202.0.0.2               # 設置共享祕鑰
# 防火牆中有兩種配置，一會在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                    # 編寫1.0到2.0的ACL
ciscoasa(config)# crypto ipsec transform-set test-set esp-aes esp-md5-hmac           # 此四條配置數據鏈接
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          # 應用到外部的邏輯接口上

ASA2配置以下

ciscoasa> en
Password:
ciscoasa# conf t
ciscoasa(config)# int e 0/0                          # 這裏我就不介紹配置含義了，和上面基本類似
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             # 另外一種配置祕鑰方式
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）配置以下

# 在ASA以前配置過到lan2區域，因此能夠以上面爲基礎接着配置
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!              # 這裏出現的警告是正常的
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配置以下（和ASA2配置基本詳細）

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:
!!!!!

二、實現lan2→lan3通訊：
ASA1配置以下

ciscoasa(config)# same-security-traffic permit intra-interface         # 容許流量進入和離開同一個接口
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配置以下

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配置以下

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:
!!!!!

三、訪問ISP
若是須要讓內網能訪問互聯網，須要在ASA上作PAT，並啓用nat控制，豁免***的流量

ASA1配置以下

ciscoasa(config)# nat-control           # 啓用nat控制
ciscoasa(config)# nat (inside) 1 0 0            # 配置pat
ciscoasa(config)# global (outside) 1 interface                # 映射到接口
# 不使用原來的ACL條目，由於有lan1_lan2和lan1_lan3,沒法同時豁免兩個，因此從新定義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                # 應用到接口

ASA2配置以下

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

ASA3配置以下

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