Configuring a VPN Using Easy VPN and an IPSec Tunnel - Cisco

wo types of VPNs are supported—site-to-site and remote access. Site-to-site VPNs are used to connect branch offices to corporate offices, for example. Remote access VPNs are used by remote clients to log in to a corporate network.

The example in this chapter illustrates the configuration of a remote access VPN that uses the Cisco Easy VPN and an IP Security (IPSec) tunnel to configure and secure the connection between the remote client and the corporate network. The figure below shows a typical deployment scenario.

Figure 1. Remote Access VPN Using IPSec Tunnel

1	Remote, networked users
2	VPN client—Cisco 860 and Cisco 880 series ISRs
3	Router—Providing the corporate office network access
4	VPN server—Easy VPN server
5	Corporate office with a network address of 10.1.1.1
6	IPSec tunnel

Cisco Easy VPN

The Cisco Easy VPN client feature eliminates much of the tedious configuration work by implementing the Cisco Unity Client protocol. This protocol allows most VPN parameters, such as internal IP addresses, internal subnet masks, DHCP server addresses, WINS server addresses, and split-tunneling flags, to be defined at a VPN server that is acting as an IPSec server.

An Easy VPN server-enabled device can terminate VPN tunnels initiated by mobile and remote workers who are running Cisco Easy VPN Remote software on PCs. Easy VPN server-enabled devices allow remote routers to act as Easy VPN Remote nodes.

The Cisco Easy VPN client feature can be configured in one of two modes—client mode or network extension mode. Client mode is the default configuration and allows only devices at the client site to access resources at the central site. Resources at the client site are unavailable to the central site. Network extension mode allows users at the central site to access network resources on the client site.

After the IPSec server has been configured, a VPN connection can be created with minimal configuration on an IPSec client, such as a supported Cisco 819, Cisco 860, and Cisco 880 series ISRs. When the IPSec client initiates the VPN tunnel connection, the IPSec server pushes the IPSec policies to the IPSec client and creates the corresponding VPN tunnel connection.

Note

The Cisco Easy VPN client feature supports configuration of only one destination peer. If your application requires creation of multiple VPN tunnels, you must manually configure the IPSec VPN and Network Address Translation/Peer Address Translation (NAT/PAT) parameters on both the client and the server.

Configuration Tasks

Perform the following tasks to configure your router for this network scenario:

•  Configuring the IKE Policy
•  Configuring Group Policy Information
•  Applying Mode Configuration to the Crypto Map
•  Enabling Policy Lookup
•  Configuring IPSec Transforms and Protocols
•  Configuring the IPSec Crypto Method and Parameters
•  Applying the Crypto Map to the Physical Interface
•  Creating an Easy VPN Remote Configuration

An example showing the results of these configuration tasks is provided in the Configuration Examples for VPN and IPSec.

Note

The procedures in this chapter assume that you have already configured basic router features as well as PPPoE or PPPoA with NAT, DCHP and VLANs. If you have not performed these configurations tasks, see Basic Router Configuration, Configuring PPP over Ethernet with NAT,Configuring PPP over ATM with NAT, and Configuring a LAN with DHCP and VLANs as appropriate for your router.

Note

The examples shown in this chapter refer only to the endpoint configuration on the Cisco 819, 860 and 880 series routers. Any VPN connection requires both endpoints to be configured properly to function. See the software configuration documentation as needed to configure the VPN for other router models.

Configuring the IKE Policy

To configure the Internet Key Exchange (IKE) policy, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto isakmp policy priority 
2.    encryption {des | 3des | aes | aes 192 | aes 256} 
3.    hash {md5 | sha} 
4.    authentication {rsa-sig | rsa-encr | pre-share}
5.    group {1 | 2 | 5}
6.    lifetime seconds 
7.    exit 

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto isakmp policy priority  Example: Router(config)# crypto isakmp policy 1	Creates an IKE policy that is used during IKE negotiation. The priority is a number from 1 to 10000, with 1 being the highest. Also enters the Internet Security Association Key and Management Protocol (ISAKMP) policy configuration mode.
Step 2	encryption {des | 3des | aes | aes 192 | aes 256}  Example: Router(config-isakmp)# encryption 3des	Specifies the encryption algorithm used in the IKE policy. The example specifies 168-bit data encryption standard (DES).
Step 3	hash {md5 | sha}  Example: Router(config-isakmp)# hash md5	Specifies the hash algorithm used in the IKE policy. The example specifies the Message Digest 5 (MD5) algorithm. The default is Secure Hash standard (SHA-1).
Step 4	authentication {rsa-sig | rsa-encr | pre-share}  Example: Router(config-isakmp)# authentication pre-share	Specifies the authentication method used in the IKE policy. The example specifies a pre-shared key.
Step 5	group {1 | 2 | 5}  Example: Router(config-isakmp)#group 2	Specifies the Diffie-Hellman group to be used in an IKE policy.
Step 6	lifetime seconds  Example: Router(config-isakmp)# lifetime 480	Specifies the lifetime, in seconds, for an IKE security association (SA). Acceptable values are from 60 to 86400.
Step 7	exit  Example: Router(config-isakmp)# exit	Exits ISAKMP policy configuration mode and returns to global configuration mode.

Configuring Group Policy Information

To configure the group policy, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto isakmp client configuration group {group-name | default}
2.    key name 
3.    dns primary-server
4.    domain name 
5.    exit 
6.    ip local pool {default | poolname} [low-ip-address [high-ip-address]]

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto isakmp client configuration group {group-name | default}  Example: Router(config)# crypto isakmp client configuration group rtr-remote Router(config-isakmp-group)#	Creates an IKE policy group containing attributes to be downloaded to the remote client. Also enters the Internet Security Association Key and Management Protocol (ISAKMP) group policy configuration mode.
Step 2	key name  Example: Router(config-isakmp-group)# key secret-password	Specifies the IKE pre-shared key for the group policy.
Step 3	dns primary-server  Example: Router(config-isakmp-group)# dns 10.50.10.1	Specifies the primary Domain Name System (DNS) server for the group. Note    To specify Windows Internet Naming Service (WINS) servers for the group, use the winscommand.
Step 4	domain name  Example: Router(config-isakmp-group)# domain company.com	Specifies group domain membership.
Step 5	exit  Example: Router(config-isakmp-group)# exit Router(config)#	Exits ISAKMP policy configuration mode and returns to global configuration mode.
Step 6	ip local pool {default | poolname} [low-ip-address [high-ip-address]]  Example: Router(config)# ip local pool dynpool 30.30.30.20 30.30.30.30	Specifies a local address pool for the group. For details about this command and additional parameters that can be set, see Cisco IOS Dial Technologies Command Reference.

Applying Mode Configuration to the Crypto Map

To apply mode configuration to the crypto map, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto map map-name isakmp authorization list list-name 
2.    crypto map tag client configuration address [initiate | respond] 

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto map map-name isakmp authorization list list-name  Example: Router(config)# crypto map dynmap isakmp authorization list rtr-remote	Applies mode configuration to the crypto map and enables key lookup (IKE queries) for the group policy from an authentication, authorization, and accounting (AAA) server.
Step 2	crypto map tag client configuration address [initiate | respond]  Example: Router(config)# crypto map dynmap client configuration address respond	Configures the router to reply to mode configuration requests from remote clients.

Enabling Policy Lookup

To enable policy lookup through AAA, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    aaa new-model 
2.    aaa authentication login {default | list-name} method1 [method2...] 
3.    aaa authorization {network | exec | commands level | reverse-access | configuration} {default | list-name} [method1[method2...]] 
4.    username name {nopassword | password password | password encryption-type encrypted-password}

DETAILED STEPS

	Command or Action	Purpose
Step 1	aaa new-model  Example: Router(config)# aaa new-model	Enables the AAA access control model.
Step 2	aaa authentication login {default | list-name} method1[method2...]  Example: Router(config)# aaa authentication login rtr-remote local	Specifies AAA authentication of selected users at login, and specifies the method used.  This example uses a local authentication database. Note    You could also use a RADIUS server for this. For details, see Cisco IOS Security Configuration Guide and Cisco IOS Security Command Reference.
Step 3	aaa authorization {network | exec | commands level |reverse-access | configuration} {default | list-name}[method1 [method2...]]  Example: Router(config)# aaa authorization network rtr-remote local	Specifies AAA authorization of all network-related service requests, including PPP, and specifies the method of authorization.  This example uses a local authorization database. Note    You could also use a RADIUS server for this. For details, see theCisco IOS Security Configuration Guide and Cisco IOS Security Command Reference.
Step 4	username name {nopassword | password password |password encryption-type encrypted-password}  Example: Router(config)# username Cisco password 0 Cisco	Establishes a username-based authentication system.

Configuring IPSec Transforms and Protocols

A transform set represents a certain combination of security protocols and algorithms. During IKE negotiation, the peers agree to use a particular transform set for protecting data flow.

During IKE negotiations, the peers search in multiple transform sets for a transform that is the same at both peers. When such a transform set is found, it is selected and applied to the protected traffic as a part of both peer configurations.

To specify the IPSec transform set and protocols, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto ipsec transform-set transform-set-name transform1 [transform2] [transform3] [transform4] 
2.    crypto ipsec security-association lifetime {seconds seconds | kilobytes kilobytes} 

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto ipsec transform-set transform-set-name transform1 [transform2][transform3] [transform4]  Example: Router(config)# crypto ipsec transform-set vpn1 esp-3des esp-sha-hmac Example:	Defines a transform set—an acceptable combination of IPSec security protocols and algorithms. See Cisco IOS Security Command Reference for details about the valid transforms and combinations.
Step 2	crypto ipsec security-association lifetime {seconds seconds | kilobyteskilobytes}  Example: Router(config)# crypto ipsec security-association lifetime seconds 86400	Specifies global lifetime values used when IPSec security associations are negotiated.

What to Do Next

Note	With manually established security associations, there is no negotiation with the peer, and both sides must specify the same transform set.

Configuring the IPSec Crypto Method and Parameters

A dynamic crypto map policy processes negotiation requests for new security associations from remote IPSec peers, even if the router does not know all the crypto map parameters (for example, IP address).

To configure the IPSec crypto method, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto dynamic-map dynamic-map-name dynamic-seq-num 
2.    set transform-set transform-set-name [transform-set-name2...transform-set-name6] 
3.    reverse-route 
4.    exit 
5.    crypto map map-name seq-num [ipsec-isakmp] [dynamic dynamic-map-name] [discover] [profile profile-name] 

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto dynamic-map dynamic-map-name dynamic-seq-num  Example: Router(config)# crypto dynamic-map dynmap 1 Router(config-crypto-map)#	Creates a dynamic crypto map entry and enters crypto map configuration mode. See Cisco IOS Security Command Reference for details about this command.
Step 2	set transform-set transform-set-name [transform-set-name2...transform-set-name6]  Example: Router(config-crypto-map)# set transform-set vpn1	Specifies which transform sets can be used with the crypto map entry.
Step 3	reverse-route  Example: Router(config-crypto-map)# reverse-route	Creates source proxy information for the crypto map entry.
Step 4	exit  Example: Router(config-crypto-map)# exit Router(config)#	Exits crypto map configuration mode and returns to global configuration mode.
Step 5	crypto map map-name seq-num [ipsec-isakmp] [dynamic dynamic-map-name] [discover] [profile profile-name]  Example: Router(config)# crypto map static-map 1 ipsec-isakmp dynamic dynmap	Creates a crypto map profile.

Applying the Crypto Map to the Physical Interface

The crypto maps must be applied to each interface through which IP Security (IPSec) traffic flows. Applying the crypto map to the physical interface instructs the router to evaluate all the traffic against the security associations database. With the default configurations, the router provides secure connectivity by encrypting the traffic sent between remote sites. However, the public interface still allows the rest of the traffic to pass and provides connectivity to the Internet.

To apply a crypto map to an interface, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    interface type number 
2.    crypto map map-name 
3.    exit 

DETAILED STEPS

	Command or Action	Purpose
Step 1	interface type number  Example: Router(config)# interface fastethernet 4 Router(config-if)#	Enters the interface configuration mode for the interface to which the crypto map applies.
Step 2	crypto map map-name  Example: Router(config-if)# crypto map static-map	Applies the crypto map to the interface. See Cisco IOS Security Command Reference for details about this command.
Step 3	exit  Example: Router(config-crypto-map)# exit Router(config)#	Exits interface configuration mode and returns to global configuration mode.

Creating an Easy VPN Remote Configuration

The router acting as the IPSec remote router must create an Easy VPN remote configuration and assign it to the outgoing interface.

To create the remote configuration, perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.    crypto ipsec client ezvpn name 
2.    group group-name key group-key 
3.    peer {ipaddress | hostname} 
4.    mode {client | network-extension | network extension plus}
5.    exit 
6.    interface type number 
7.    crypto ipsec client ezvpn name [outside | inside] 
8.    exit 

DETAILED STEPS

	Command or Action	Purpose
Step 1	crypto ipsec client ezvpn name  Example: Router(config)# crypto ipsec client ezvpn ezvpnclient Router(config-crypto-ezvpn)#	Creates a Cisco Easy VPN remote configuration, and enters Cisco Easy VPN remote configuration mode.
Step 2	group group-name key group-key  Example: Router(config-crypto-ezvpn)# group ezvpnclient key secret-password Router(config-crypto-ezvpn)#	Specifies the IPSec group and IPSec key value for the VPN connection.
Step 3	peer {ipaddress | hostname}  Example: Router(config-crypto-ezvpn)# peer 192.168.100.1 Router(config-crypto-ezvpn)#	Specifies the peer IP address or hostname for the VPN connection. Note    A hostname can be specified only when the router has a DNS server available for hostname resolution.
Step 4	mode {client | network-extension | network extension plus}  Example: Router(config-crypto-ezvpn)# mode client Router(config-crypto-ezvpn)#	Specifies the VPN mode of operation.
Step 5	exit  Example: Router(config-crypto-ezvpn)# exit Router(config)#	Exits Cisco Easy VPN remote configuration mode and returns to global configuration mode.
Step 6	interface type number  Example: Router(config)# interface fastethernet 4 Router(config-if)#	Enters the interface configuration mode for the interface to which the Cisco Easy VPN remote configuration applies. Note    For routers with an ATM WAN interface, this command would beinterface atm 0.
Step 7	crypto ipsec client ezvpn name [outside | inside]  Example: Router(config-if)# crypto ipsec client ezvpn ezvpnclient outside Router(config-if)#	Assigns the Cisco Easy VPN remote configuration to the WAN interface. This command causes the router to automatically create the NAT or port address translation (PAT) and access list configuration needed for the VPN connection.
Step 8	exit  Example: Router(config-crypto-ezvpn)# exit Router(config)#	Exits interface configuration mode and returns to global configuration mode.

Verifying Your Easy VPN Configuration

Router# show crypto ipsec client ezvpn
Tunnel name :ezvpnclient
Inside interface list:vlan 1
Outside interface:fastethernet 4
Current State:IPSEC_ACTIVE
Last Event:SOCKET_UP
Address:8.0.0.5
Mask:255.255.255.255
Default Domain:cisco.com

Configuration Examples for VPN and IPSec

The following configuration example shows a portion of the configuration file for the VPN and IPSec tunnel described in this chapter.

!
aaa new-model
!
aaa authentication login rtr-remote local
aaa authorization network rtr-remote local
aaa session-id common
!
username Cisco password 0 Cisco
!
crypto isakmp policy 1
 encryption 3des
 authentication pre-share
 group 2
 lifetime 480
!
crypto isakmp client configuration group rtr-remote
 key secret-password
 dns 10.50.10.1 10.60.10.1
 domain company.com
 pool dynpool
!
crypto ipsec transform-set vpn1 esp-3des esp-sha-hmac
!
crypto ipsec security-association lifetime seconds 86400
!
crypto dynamic-map dynmap 1
 set transform-set vpn1
 reverse-route
!
crypto map static-map 1 ipsec-isakmp dynamic dynmap
crypto map dynmap isakmp authorization list rtr-remote
crypto map dynmap client configuration address respond
crypto ipsec client ezvpn ezvpnclient
 connect auto
 group 2 key secret-password
 mode client
 peer 192.168.100.1
!
interface fastethernet 4
 crypto ipsec client ezvpn ezvpnclient outside
 crypto map static-map
!
interface vlan 1
 crypto ipsec client ezvpn ezvpnclient inside
!

Top

Was this Document Helpful?

 Feedback

Viewers of This Document Also Viewed

• Configuration Professional: Site-to-Site IPsec VPN Between Two IOS Routers Configuration Example
• Site-to-Site and Extranet VPN Business Scenarios
• LAN-to-LAN IPsec Tunnel Between Two Routers Configuration Example

Let Us Help

• Open a Support Case
• (Requires a Cisco Service Contract)

Ready to Replace an Old Switch?

Upgrade your network and get discounts on replacement switches and support services

Learn How

Related Support Community Discussions

• test throughput with null:- equal to /dev/null?

  Last Reply 6 months ago

  in Network Management
• UCCE 9 ICM ECC variables can't map to CVP

  Last Reply 2 years ago

  in Contact Center
• CUIC sql button on Historical Reports

  Last Reply 2 months ago

  in Contact Center

Cisco Support Community

Share