Cisco 870-Series Router Manual PDF (Setup & Configuration Guide)

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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 7

Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation

Configure a VPN

Configure the IKE Policy

Perform these steps to configure the Internet Key Exchange (IKE) policy, beginning in global

configuration mode:

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 Internet Security Association and Key

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 uses 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 uses 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

the IKE policy.

Step 6

lifetime

seconds

Example:

Router(config-isakmp)#

lifetime

480

Router(config-isakmp)#

Specifies the lifetime, 60–86400 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.

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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 7

Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation

Configure a VPN

Configure Group Policy Information

Perform these steps to configure the group policy, beginning in global configuration mode:

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 that contains

attributes to be downloaded to the remote client.

Also enters Internet Security Association Key

Management Protocol (ISAKMP) 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 Service

(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 the

Cisco IOS Dial

Technologies Command Reference

.

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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 7

Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation

Configure a VPN

Enable Policy Lookup

Perform these steps to enable policy lookup through AAA, beginning in global configuration mode:

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. See

the

Cisco IOS Security Configuration Guide

and

the

Cisco IOS Security Command Reference

for

details.

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 the method used to do so.

This example uses a local authorization database.

You could also use a RADIUS server for this. See

the

Cisco IOS Security Configuration Guide

and

the

Cisco IOS Security Command Reference

for

details.

Step 4

username

name

{

nopassword

|

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.

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Chapter 7

Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation

Configure a VPN

Perform these steps to specify the IPSec transform set and protocols, beginning in global configuration

mode:

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 the

Cisco IOS Security Command Reference

for detail about the valid transforms and

combinations.

Step 2

crypto ipsec security-association lifetime

{

seconds

|

kilobytes

}

Example:

Router(config)#

crypto ipsec

security-association lifetime seconds

86400

Router(config)#

Specifies global lifetime values used when

negotiating IPSec security associations.

See the

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:

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 the

Cisco IOS Security Command Reference

for more detail 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.

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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 7

Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation

Configure a VPN

Apply the Crypto Map to the Physical Interface

The crypto maps must be applied to each interface through which 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:

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 the

Cisco IOS Security Command Reference

for details.

Step 4

exit

Example:

Router(config-crypto-map)#

exit

Router(config)#

Enters 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.

Command or Action

Purpose

Command or Action

Purpose

Step 1

interface

type number

Example:

Router(config)#

interface

fastethernet 4

Router(config-if)#

Enters interface configuration mode for the

interface to which you want to apply the crypto

map.

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