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Establishing an IPSec Tunnel Through Negotiation Initiated by AR with a Dynamic IP Address to the C3900e(Using Dynamic Crypto Map Entry) Highlighted

Latest reply: Feb 24, 2017 07:32:26 1712 1 2 0 0


This example applies to all versions and routers.

This example applies to routers of all versions.

Networking Requirements

As shown in Figure 1, RouterA is the enterprise branch gateway, the public network interface dynamically obtains an IP address, 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 dynamic crypto map entry to establish an IPSec tunnel with the branch gateway.

Figure 1 Networking for establishing an IPSec tunnel through negotiation initiated by the branch gateway with a dynamic IP address to the headquarters Cisco router



Step 1 Configure RouterA.


MD5, SHA-1, DES, and 3DES have potential security risks. Exercise caution when you use them.

The commands used to configure IKE peers and the IKE protocol differ depending on the software version.

l In earlier versions of V200R008:

ike peer peer-name [ v1 | v2 ]

l In V200R008 and later versions:

l To configure IKE peers: ike peer peer-name

l To configure the IKE protocol: 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.

sysname RouterA //Configure the device name.
ipsec authentication sha2 compatible enable
acl number 3000 //Specify data flows (traffic from the branch subnet to the headquarters subnet) to be protected.
rule 5 permit ip source destination
ipsec proposal prop1 //Configure an IPSec proposal.
esp authentication-algorithm sha2-256
esp 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 group14
authentication-algorithm sha2-256
ike peer peer1 v1 //Configure an IKE peer.
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 1
remote-address //Use the IP address to identify the IKE peer.
ipsec policy policy1 10 isakmp //Configure an IPSec policy.
security acl 3000
ike-peer peer1
proposal prop1
interface GigabitEthernet0/0/1
ipsec policy policy1 //Apply the IPSec policy to 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 DHCP
server function on the device directly connected or having a reachable route to RouterA. For detailed configurations, see the product documentation
of the device used.
interface GigabitEthernet0/0/2
ip address

Step 2 Configure RouterB.

hostname RouterB //Configure the device name.
crypto isakmp policy 1
encryption aes 128
hash sha256
authentication pre-share
group 14
crypto isakmp key huawei@1234 address //Configure the pre-shared key as huawei@1234, use the IP address to identify an IKE peer, and configure the device to allow access from any branch.
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 p1
match address 102
crypto map p1 1 ipsec-isakmp dynamic p1 //Configure an IPSec policy.
interface GigabitEthernet0/0
ip address
duplex auto
speed auto
crypto map p1 //Apply the IPSec policy to the interface.
interface GigabitEthernet0/1
ip address
duplex auto
speed auto
ip route //Configure a static route to ensure reachability at both ends.
access-list 102 permit ip //Specify data flows (traffic from the headquarters subnet to the branch subnet) to be protected.

Step 3 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.


Configuration Notes

In this example, the commands on the Cisco router are recommended ones. The product version is Cisco IOS Software, C3900e Software (C3900e-UNIVERSALK9-M), Version 15.2(4)M1, RELEASE SOFTWARE (fc1). For details, visit

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Created Feb 24, 2017 07:32:26

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