Cisco 819 Integrated Services Routers Software Configuration Guide
Configuring a VPN Using Easy VPN and an IPSec Tunnel
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Configuring a VPN Using Easy VPN and an IPSec Tunnel

Table Of Contents

Configuring a VPN Using Easy VPN and an IPSec Tunnel

Cisco Easy VPN

Configuration Tasks

Configure the IKE Policy

Configure Group Policy Information

Apply Mode Configuration to the Crypto Map

Enable Policy Lookup

Configure IPSec Transforms and Protocols

Configure the IPSec Crypto Method and Parameters

Apply the Crypto Map to the Physical Interface

Create an Easy VPN Remote Configuration

Verifying Your Easy VPN Configuration

Configuration Example


Configuring a VPN Using Easy VPN and an IPSec Tunnel


This chapter provides an overview of the creation of Virtual Private Networks (VPNs) that can be configured on the Cisco 819 Integrated Services Routers (ISRs).

Cisco routers and other broadband devices provide high-performance connections to the Internet, but many applications also require the security of VPN connections that perform a high level of authentication and that encrypt the data between two particular endpoints.

Two 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 IPSec tunnel to configure and secure the connection between the remote client and the corporate network. Figure 13-1 shows a typical deployment scenario.

Figure 13-1 Remote Access VPN Using IPSec Tunnel

1

Remote, networked users

2

VPN client—Cisco 819 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 ISR. 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 the 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:

Configure the IKE Policy

Configure Group Policy Information

Apply Mode Configuration to the Crypto Map

Enable Policy Lookup

Configure IPSec Transforms and Protocols

Configure the IPSec Crypto Method and Parameters

Apply the Crypto Map to the Physical Interface

Create an Easy VPN Remote Configuration

An example showing the results of these configuration tasks is provided in the "Configuration Example" section.


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" section.



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


Configure the IKE Policy

Perform these steps to configure the Internet Key Exchange (IKE) policy, 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
Router(config-isakmp)# 
 
        

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
Router(config-isakmp)# 
 
        

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
Router(config-isakmp)# 
 
        

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
Router(config-isakmp)# 
 
        

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
Router(config-isakmp)# 
 
        

Specifies the Diffie-Hellman group to be used in an IKE policy.

Step 6 

lifetime seconds

Example:

Router(config-isakmp)# lifetime 480
Router(config-isakmp)# 
 
        

Specifies the lifetime, 60 to 86400 seconds, for an IKE security association (SA).

Step 7 

exit

Example:

Router(config-isakmp)# exit
Router(config)# 
 
        

Exits IKE policy configuration mode and enters global configuration mode.

Configure Group Policy Information

Perform these steps to configure the group policy, 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
Router(config-isakmp-group)# 
 
        

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
Router(config-isakmp-group)# 
 
        

Specifies the primary Domain Name System (DNS) server for the group.

Note You may also want to specify Windows Internet Naming Service (WINS) servers for the group by using the wins command.

Step 4 

domain name

Example:

Router(config-isakmp-group)# domain 
company.com
Router(config-isakmp-group)# 
 
        

Specifies group domain membership.

Step 5 

exit

Example:

Router(config-isakmp-group)# exit
Router(config)# 
 
        

Exits IKE group policy configuration mode and enters 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
Router(config)# 
 
        

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.

Apply Mode Configuration to the Crypto Map

Perform these steps to apply mode configuration to the crypto map, 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
Router(config)# 
 
        

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
Router(config)# 
 
        

Configures the router to reply to mode configuration requests from remote clients.

Enable Policy Lookup

Perform these steps to enable policy lookup through AAA, 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
Router(config)# 
 
        

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
Router(config)# 
 
        

Specifies AAA authentication of selected users at login, and specifies the method used.

This example uses a local authentication database. You could also use a RADIUS server for this. For details, see Securing User Services Configuration Guide Library, Cisco IOS Release 12.4T 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
Router(config)# 
 
        

Specifies AAA authorization of all network-related service requests, including PPP, and specifies the method of authorization.

This example uses a local authorization database. You could also use a RADIUS server for this. For details, see Securing User Services Configuration Guide Library, Cisco IOS Release 12.4T 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
Router(config)# 
 
        

Establishes a username-based authentication system.

This example implements a username of Cisco with an encrypted password of Cisco.

Configure 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 peers' configurations.

Perform these steps to specify the IPSec transform set and protocols, 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
Router(config)# 
 
        

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 | kilobytes kilobytes}

Example:

Router(config)# crypto ipsec 
security-association lifetime seconds 86400
Router(config)# 
 
        

Specifies global lifetime values used when IPSec security associations are negotiated.

See Cisco IOS Security Command Reference for details.


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


Configure 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).

Perform these steps to configure the IPSec crypto method, 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 more 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
Router(config-crypto-map)# 
 
        

Specifies which transform sets can be used with the crypto map entry.

Step 3 

reverse-route

Example:

Router(config-crypto-map)# reverse-route
Router(config-crypto-map)# 
 
        

Creates source proxy information for the crypto map entry.

See Cisco IOS Security Command Reference for details.

Step 4 

exit

Example:

Router(config-crypto-map)# exit
Router(config)# 
 
        

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
Router(config)# 
 
        

Creates a crypto map profile.

Apply 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.

Perform these steps to apply a crypto map to an interface, 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 you want the crypto map applied.

Step 2 

crypto map map-name

Example:

Router(config-if)# crypto map static-map
Router(config-if)# 
 
        

Applies the crypto map to the interface.

See Cisco IOS Security Command Reference for more details about this command.

Step 3 

exit

Example:

Router(config-crypto-map)# exit
Router(config)# 
 
        

Returns to global configuration mode.

Create 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.

Perform these steps to create the remote configuration, 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)# 
 
        

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 you want the Cisco Easy VPN remote configuration applied.

Note For routers with an ATM WAN interface, this command would be interface 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, causing 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)# 
 
        

Returns to global configuration mode.

Verifying Your Easy VPN Configuration

The following example verifies your easy vpn connection:

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 Example

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
!