鏈路備份的IPSec VPN和裝置備份的IPSec VPN：
首先實驗的是鏈路備份的  IPSec VPN，下面是實驗拓撲：


IP地址配置：
R1（Branch）：
Branch(config-if)#ip add 12.1.1.1 255.255.255.0
Branch(config-if)#no shu
Branch(config-if)#int lo0
Branch(config-if)#ip add 1.1.1.1 255.255.255.0
Branch#conf t
Branch(config)#ip route 0.0.0.0 0.0.0.0 12.1.1.2
R2（Internet）：
R2(config)#int f1/0
R2(config-if)#ip add 12.1.1.2 255.255.255.0
R2(config-if)#no shu
R2(config)#int f1/1
R2(config-if)#ip add 23.1.1.2 255.255.255.0
R2(config-if)#no shu
R2(config-if)#int f2/0
R2(config-if)#ip add 24.1.1.2 255.255.255.0
R2(config-if)#no shu
R2(config-if)#int lo0
R2(config-if)#ip add 2.2.2.2 255.255.255.0
R3（Primary）：
R3(config)#int f1/0
R3(config-if)#ip add 23.1.1.3 255.255.255.0
R3(config-if)#no shu
R3(config-if)#int f1/1
R3(config-if)#ip add 10.1.1.3 255.255.255.0
R3(config-if)#no shu
R3(config-if)#int l0
R3(config-if)#ip add 3.3.3.3 255.255.255.0
R3(config-if)#end
R3(config)#router os 1
R3(config-router)#router-id 3.3.3.3
R3(config-router)#net 10.1.1.0 0.0.0.255 a 0
Primary(config)#ip route 0.0.0.0 0.0.0.0 23.1.1.2
R4（Secondary）：
R4(config)#int f1/0
R4(config-if)#ip add 24.1.1.4 255.255.255.0
R4(config-if)#no shu
R4(config-if)#int f1/1
R4(config-if)#ip add 10.1.1.4 255.255.255.0
R4(config-if)#no shu
R4(config-if)#int l0
R4(config-if)#ip add 4.4.4.4 255.255.255.0
R4(config-if)#router os 1
R4(config-router)#router-id 4.4.4.4
R4(config-router)#net 10.1.1.0 0.0.0.255 a 0
R4(config)#ip route 0.0.0.0 0.0.0.0 24.1.1.2
R5（Server）：
R5(config)#int f1/0
R5(config-if)#ip add 10.1.1.5 255.255.255.0
R5(config-if)#no shu
R5(config-if)#int l0
R5(config-if)#ip add 5.5.5.5 255.255.255.0  
R5(config-if)#router os 1
R5(config-router)#router-id 5.5.5.5
R5(config-router)#net 0.0.0.0 255.255.255.255 a 0
鏈路備份的IPSec VPN配置：

Branch(config)#crypto is po 10
Branch(config-isakmp)#authentication  pre-share
Branch(config-isakmp)#exi
Branch(config)#crypto isakmp  key  0 cisco address 23.1.1.3
Branch(config)#crypto isakmp  key  0 cisco address 24.1.1.4 //金鑰可以不一樣
Branch(config)#crypto isakmp keepalive 10 periodic //啟用DPD
Branch(config)#ip access-list extended vpn
Branch(config-ext-nacl)#permit  ip 1.1.1.0 0.0.0.255 5.5.5.0 0.0.0.255
Branch(config-ext-nacl)#exi
Branch(config)#crypto ipsec transform-set trans esp-des esp-md5-hmac
Branch(cfg-crypto-trans)#exi
Branch(config)#crypto map cisco 10 ipsec-isakmp
% NOTE: This new crypto map will remain disabled until a peer
        and a valid access list have been configured.
Branch(config-crypto-map)#match address vpn
Branch(config-crypto-map)#set peer 23.1.1.3 //先配置23.1.1.3為主用閘道器，後配置的24.1.1.4為備用的閘道器
Branch(config-crypto-map)#set peer 24.1.1.4
Branch(config-crypto-map)#set transform-set trans
Branch(config-crypto-map)#int f1/0
Branch(config-if)#crypto map cisco
Primary(config)#crypto  isakmp  po 10
Primary(config-isakmp)#au pre-share
Primary(config-isakmp)#exi
Primary(config)#crypto isakmp  key 0 cisco address 12.1.1.1
Primary(config)#crypto isakmp  keepalive 10 periodic //開啟DPD
Primary(config)#ip access-list extended vpn
Primary(config-ext-nacl)#permit  ip 5.5.5.0 0.0.0.255 1.1.1.0 0.0.0.255
Primary(config-ext-nacl)#exi
Primary(config)#crypto  ipsec  transform-set trans esp-des esp-md5-hmac
Primary(cfg-crypto-trans)#exi
Primary(config)#crypto  map cisco 10 ipsec-isakmp
% NOTE: This new crypto map will remain disabled until a peer
        and a valid access list have been configured.
Primary(config-crypto-map)#match address vpn
Primary(config-crypto-map)#set peer 12.1.1.1
Primary(config-crypto-map)#set transform-set trans
Primary(config-crypto-map)#reverse-route
Primary(config-crypto-map)#set reverse-route tag 10//啟用RRI，並解決回包問題
This will remove previously installed VPN routes and SAs
Primary(config-crypto-map)#int f1/0
Primary(config-if)#crypto map cisco
*Apr 23 14:15:21.343: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON
Primary(config-if)#router os 1
Primary(config-router)#redistribute static route-map RRI subnets
Primary(config-router)#exi
Primary(config)#route-map RR1
Primary(config-route-map)#match tag 10
Primary(config-route-map)#exi
Secondary(config)#crypto isakmp  po 10
Secondary(config-isakmp)#authentication  pre-share
Secondary(config)#crypto  isakmp key 0 cisco address 12.1.1.1
Secondary(config)#exi
Secondary(config)#ip access-list extended vpn
Secondary(config-ext-nacl)#permit ip 5.5.5.0 0.0.0.255 1.1.1.0 0.0.0.255
Secondary(config-ext-nacl)#exi
Secondary(config)#crypto isakmp  keepalive 10 periodic
Secondary(config)#crypto  ipsec  transform-set trans esp-des esp-md5-hmac
Secondary(cfg-crypto-trans)#exi
Secondary(config)#crypto  map cisco 10 ipsec-isakmp
% NOTE: This new crypto map will remain disabled until a peer
        and a valid access list have been configured.
Secondary(config-crypto-map)#match address vpn
Secondary(config-crypto-map)#set peer 12.1.1.1
Secondary(config-crypto-map)#set transform-set trans
Secondary(config-crypto-map)#reverse-route   
Secondary(config-crypto-map)#set reverse-route tag  10
This will remove previously installed VPN routes and SAs
Secondary(config-crypto-map)#int f1/0
Secondary(config-if)#crypto  map cisco
*Apr 23 14:17:47.915: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON
Secondary(config-if)#router os 1
Secondary(config-router)#redistribute static subnets route-map RRI
Secondary(config-router)#exi
Secondary(config)#route-map RRI
Secondary(config-route-map)#match  tag 10
Secondary(config-route-map)#exi
Primary(config)#int f1/0
Primary(config-if)#shu
Secondary#sho crypto en connections active
Crypto Engine Connections

   ID  Type    Algorithm           Encrypt  Decrypt LastSeqN IP-Address
    1  IPsec   DES+MD5                   0       26       31 24.1.1.4
    2  IPsec   DES+MD5                  26        0        0 24.1.1.4
 1001  IKE     SHA+DES                   0        0        0 24.1.1.4
這裡說一下，當Primary這邊的介面down了的話，隨著安全關聯的消失，反向注入產生的路由也跟隨者消失了。還有，鏈路備份的高可用性IPSec VPN是不支援搶佔的。
Server#sho ip ro ospf
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is not set

      1.0.0.0/24 is subnetted, 1 subnets
O E2     1.1.1.0 [110/20] via 10.1.1.4, 00:01:22, FastEthernet1/0

現在來做一下裝置的備份，裝置備份的IPSec VPN（Redundancy VPN）：
redundancy VPN主要是使用HSRP來提供裝置級別的備份，實驗拓撲如下：

裝置IP地址配置：
R1:
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
interface FastEthernet1/0
 ip address 12.1.1.1 255.255.255.0
 duplex auto
 speed auto
 crypto map cisco
 !
ip route 0.0.0.0 0.0.0.0 12.1.1.2
R2:
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface FastEthernet1/0
 ip address 12.1.1.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/1
 ip address 10.1.1.2 255.255.255.0
 duplex auto
 speed auto
R3:
interface Loopback0
 ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet1/0
 ip address 10.1.1.3 255.255.255.0
 duplex auto
 speed auto
 standby 1 ip 10.1.1.100
 standby 1 priority 105
 standby 1 preempt
 standby 1 name cisco
 crypto map cisco redundancy cisco
 !
!
interface FastEthernet1/1
 ip address 20.1.1.3 255.255.255.0
 duplex auto
 speed auto
 !
!         
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 redistribute static subnets route-map RRI
 network 20.1.1.0 0.0.0.255 area 0
!
ip route 0.0.0.0 0.0.0.0 10.1.1.2
!
ip access-list extended vpn
 permit ip 5.5.5.0 0.0.0.255 1.1.1.0 0.0.0.255
!
route-map RRI permit 10
 match tag 10
R4
interface Loopback0
 ip address 4.4.4.4 255.255.255.0
 !
interface FastEthernet1/0
 ip address 10.1.1.4 255.255.255.0
 duplex auto
 speed auto
 standby 1 ip 10.1.1.100
 standby 1 preempt
 standby 1 name cisco
 crypto map cisco
 !
!
interface FastEthernet1/1
 ip address 20.1.1.4 255.255.255.0
 duplex auto
 speed auto
 !
!
router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 redistribute static subnets route-map RRI
 network 20.1.1.0 0.0.0.255 area 0
ip route 0.0.0.0 0.0.0.0 10.1.1.2
!
route-map RRI permit 10
 match tag 10
interface Loopback0
 ip address 5.5.5.5 255.255.255.0
 !
interface FastEthernet1/0
 ip address 20.1.1.5 255.255.255.0
 duplex auto
 speed auto
 !
router ospf 1
 router-id 5.5.5.5
 log-adjacency-changes
 network 5.5.5.0 0.0.0.255 area 0
 network 20.1.1.0 0.0.0.255 area 0
HSRP配置：
R3:
interface FastEthernet1/0
 ip address 10.1.1.3 255.255.255.0
 duplex auto
 speed auto
 standby 1 ip 10.1.1.100
 standby 1 priority 105
 standby 1 preempt
 standby 1 name cisco
R4:
interface FastEthernet1/0
 ip address 10.1.1.4 255.255.255.0
 duplex auto
 speed auto
 standby 1 ip 10.1.1.100
 standby 1 preempt
 standby 1 name cisco
 crypto map cisco
IPSec VPN配置：
R1:
crypto isakmp policy 10
 authentication pre-share
crypto isakmp key cisco address 10.1.1.100
crypto isakmp keepalive 10 periodic
!
!
crypto ipsec transform-set trans esp-des esp-md5-hmac
!
crypto map cisco 10 ipsec-isakmp
 set peer 10.1.1.100
 set transform-set trans
 match address vpn
!
ip access-list extended vpn
 permit ip 1.1.1.0 0.0.0.255 5.5.5.0 0.0.0.255
!
R3：
crypto isakmp policy 10
 authentication pre-share
crypto isakmp key cisco address 12.1.1.1
crypto isakmp keepalive 10 periodic
!
!
crypto ipsec transform-set trans esp-des esp-md5-hmac
!
crypto map cisco 10 ipsec-isakmp
 set peer 12.1.1.1
 set transform-set trans
 set reverse-route tag 10
 match address vpn
 reverse-route static //若沒有這個關鍵字，必須要有IPSec SA才會產生反向路由，主要，active路由器才會產生反向路由
interface FastEthernet1/0
 crypto map cisco redundancy cisco //只用redundancy關鍵字呼叫HSRP的名字，哪臺為活動的路由器就會使用虛擬IP和遠端的peer建立IPSec VPN
ip access-list extended vpn                             
 permit ip 5.5.5.0 0.0.0.255 1.1.1.0 0.0.0.255
!
Redundancy VPN是支援搶佔的，因為HSRP支援搶佔（當然前提是要開啟preempt）
R4：
crypto isakmp policy 10
 authentication pre-share
crypto isakmp key cisco address 12.1.1.1
crypto isakmp keepalive 10 periodic
!
!
crypto ipsec transform-set trans esp-des esp-md5-hmac
!
crypto map cisco 10 ipsec-isakmp
 set peer 12.1.1.1
 set transform-set trans
 set reverse-route tag 10
 match address vpn
 reverse-route static
interface FastEthernet1/0
 crypto map cisco redundancy cisco
ip access-list extended vpn
 permit ip 5.5.5.0 0.0.0.255 1.1.1.0 0.0.0.255

R1#ping 5.5.5.5 so 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!.!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 288/523/748 ms

R3#sho cry en conn active
Crypto Engine Connections

   ID  Type    Algorithm           Encrypt  Decrypt LastSeqN IP-Address
    1  IPsec   DES+MD5                   0        5        5 10.1.1.100
    2  IPsec   DES+MD5                   5        0        0 10.1.1.100
 1001  IKE     SHA+DES                   0        0        0 10.1.1.100
R5#sho ip ro ospf
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is not set

      1.0.0.0/24 is subnetted, 1 subnets
O E2     1.1.1.0 [110/20] via 20.1.1.3, 00:23:00, FastEthernet1/0
R3#sho ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is 10.1.1.2 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 10.1.1.2
      1.0.0.0/24 is subnetted, 1 subnets
S        1.1.1.0 [1/0] via 12.1.1.1
      3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        3.3.3.0/24 is directly connected, Loopback0
L        3.3.3.3/32 is directly connected, Loopback0
      5.0.0.0/32 is subnetted, 1 subnets
O        5.5.5.5 [110/2] via 20.1.1.5, 00:27:56, FastEthernet1/1
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.1.1.0/24 is directly connected, FastEthernet1/0
L        10.1.1.3/32 is directly connected, FastEthernet1/0
      20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        20.1.1.0/24 is directly connected, FastEthernet1/1
L        20.1.1.3/32 is directly connected, FastEthernet1/1
測試一下裝置切換：
可以將R3重啟reload或者將介面shutdown
R3(config)#int f1/0
R3(config-if)#shu

R4#
*Apr 23 19:21:43.491: %HSRP-5-STATECHANGE: FastEthernet1/0 Grp 1 state Standby -> Active
R1#ping 5.5.5.5 so 1.1.1.1  repeat  1000

Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!!!!!...........!!!!!!!!!!!.!!!!!!.
Success rate is 66 percent (26/39), round-trip min/avg/max = 236/432/644 ms