As shown in Figure Networking for establishing an IPSec tunnel through negotiation initiated by the branch gateway with a dynamic IP address to the headquarters Cisco router, RouterA is the enterprise branch gateway, NAT is deployed on the outbound interface of RouterA, and RouterB is the enterprise headquarters gateway (Cisco router). The branch and headquarters communicate through the public network.
The enterprise wants to protect data flows between the branch subnet and the headquarters subnet. Because the branch gateway dynamically obtains an IP address, the headquarters gateway can use the host name to establish an IPSec tunnel with the branch gateway.
IPSec and NAT are both configured on the outbound interface of the branch gateway, so traffic to be protected is processed by NAT and IPSec in sequence. You can add ACL rules used by NAT to deny traffic to be protected by IPSec so that the traffic is only encrypted by IPSec.
Figure1 Networking for establishing an IPSec tunnel through negotiation initiated by the branch gateway with a dynamic IP address to the headquarters Cisco router
Procedure
Configure RouterA.
#sysname RouterA //Configure the device name.#ipsec authentication sha2 compatible enable#ike local-name huawei#acl number 3000 //Specify data flows (traffic from the branch subnet to the headquarters subnet) to be protected.rule 5 permit ip source 10.1.1.0 0.0.0.255 destination 10.1.2.0 0.0.0.255#acl number 3001 //Configure an ACL to deny data flows to be protected.rule 5 deny ip source 10.1.1.0 0.0.0.255 destination 10.1.2.0 0.0.0.255rule 10 permit ip#ipsec proposal prop1 //Configure an IPSec proposal.esp authentication-algorithm sha2-256esp encryption-algorithm aes-128#ike proposal 1 //Configure an IKE proposal.encryption-algorithm aes-cbc-128 //In V200R008 and later versions, the aes-cbc-128 parameter is changed to aes-128.dh group14authentication-algorithm sha2-256#ike peer peer1 v1 //The commands used to configure IKE peers and the IKE protocol differ depending on the software version. In earlier versions of V200R008, the command is ike peer peer-name [ v1 | v2 ]. In V200R008 and later versions, the command is ike peer peer-name and version { 1 | 2 }. By default, IKEv1 and IKEv2 are enabled simultaneously. An initiator uses IKEv2 to initiate a negotiation request, while a responder uses IKEv1 or IKEv2 to respond. To initiate a negotiation request using IKEv1, run the undo version 2 command.exchange-mode aggressive //Configure the aggressive mode.pre-shared-key cipher %@%@W'KwGZ8`tQ8s^C8q(qC"0(;@%@%@%#%#@W4p8i~Mm5sn;9Xc&U#(cJC;.CE|qCD#jAH&/#nR%#%# //Configure the pre-shared key as huawei@1234.ike-proposal 1local-id-type name //Configure the local ID type for IKE negotiation. In V200R008 and later versions, the name parameter is changed to fqdn.remote-name RouterB //Configure the IKE peer name. In V200R008 and later versions, the device does not support the remote-name command. This command provides teh same function as the remote-id command.remote-address 60.1.2.1#ipsec policy policy1 10 isakmp //Configure an IPSec policy.security acl 3000ike-peer peer1proposal prop1#interface GigabitEthernet0/0/1ipsec policy policy1 //Apply the IPSec policy to the interface.nat outbound 3001 //Configure NAT on the interface.ip address dhcp-alloc //Enable the DHCP client function to allow the branch gateway to dynamically obtain an IP address. In addition, you also need to configure the DHCPserver function on the device directly connected or having a reachable route to RouterA. For detailed configurations, see the product documentationof the device used.#interface GigabitEthernet0/0/2ip address 10.1.1.1 255.255.255.0#returnConfigure RouterB.
!hostname RouterB //Configure the device name.!crypto isakmp policy 1encryption aes 128hash sha256authentication pre-sharegroup 14crypto isakmp key huawei@1234 hostname huawei //Configure the pre-shared key as huawei@1234.!crypto isakmp identity hostname //Set the local ID type in IKE negotiation to hostname.!crypto ipsec transform-set p1 esp-sha256-hmac esp-aes 128 //Configure a security algorithm used by IPSec.!!crypto dynamic-map p1 1 //Create a dynamic crypto map entry.set transform-set p1match address 102!!crypto map p1 1 ipsec-isakmp dynamic p1 //Configure an IPSec policy.!!interface GigabitEthernet0/0ip address 60.1.2.1 255.255.255.0duplex autospeed autocrypto map p1 //Apply the IPSec policy to the interface.!interface GigabitEthernet0/1ip address 10.1.2.1 255.255.255.0duplex autospeed auto!!ip route 0.0.0.0 0.0.0.0 60.1.2.2 //Configure a static route to ensure reachability at both ends.!access-list 102 permit ip 10.1.2.0 0.0.0.255 10.1.1.0 0.0.0.255 //Specify data flows (traffic from the headquarters subnet to the branch subnet) to be protected.!end
Verify the configuration.
# After the configuration is complete, run the ping command on PC A. PC B can be pinged.
# Run the display ike sa and display ipsec sa commands on RouterA, and run the show crypto isakmp sa and show crypto ipsec sa commands on RouterB. You can see that the IPSec tunnel is created successfully.
# Run the display ipsec statistics command on RouterA to check data packet statistics.
