Friday, 6 December 2019

Configure Remote Access IPsec VPNs at Cisco ASA firewall via CLI

Configure Remote Access IPsec VPNs


This section describes how to configure remote access VPNs.


Configure Interfaces

An ASA has at least two interfaces, referred to here as outside and inside. Typically, the outside interface is connected to the public Internet, while the inside interface is connected to a private network and is protected from public access.
To begin, configure and enable two interfaces on the ASA. Then assign a name, IP address and subnet mask. Optionally, configure its security level, speed and duplex operation on the security appliance.

Procedure :-


Step 1
Enter interface configuration mode from global configuration mode.
interface {interface}
Example:
hostname(config)# interface ethernet0
hostname(config-if)#



Step 2
Set the IP address and subnet mask for the interface.
ip address ip_address [mask] [standby ip_address]
Example:
hostname(config)# interface ethernet0
hostname(config-if)# ip address 10.10.4.200 255.255.0.0



Step 3
Specify a name for the interface (maximum of 48 characters). You cannot change this name after you set it.
nameif name
Example:
hostname(config-if)# nameif outside
hostname(config-if)#



Step 4
Enable the interface. By default, interfaces are disabled.shutdown
Example:
hostname(config-if)# no shutdown
hostname(config-if)#


Configure ISAKMP Policy and Enabling ISAKMP on the Outside Interface
Procedure





Step 1
Specify the authentication method and the set of parameters to use during IKEv1 negotiation.
Priority uniquely identifies the Internet Key Exchange (IKE) policy and assigns a priority to the policy. Use an integer from 1 to 65,534, with 1 being the highest priority and 65,534 the lowest.
In the steps that follow, we set the priority to 1.


Step 2
Specify the encryption method to use within an IKE policy.
crypto ikev1 policy priority encryption {aes | aes-192 | aes-256 | des | 3des}
Example:
hostname(config)#
 crypto ikev1 policy 1 encryption 3des

hostname(config)#



Step 3
Specify the hash algorithm for an IKE policy (also called the HMAC variant).

crypto ikev1 policy
 priority hash {md5 | sha}
Example:
hostname(config)# crypto ikev1 policy 1 hash sha
hostname(config)#



Step 4
Specify the Diffie-Hellman group for the IKE policy—the crypto protocol that allows the IPsec client and the ASA to establish a shared secret key.
crypto ikev1 policy priority group {1 | 2 | 5| }
Example:
hostname(config)# crypto ikev1 policy 1 group 2
hostname(config)#



Step 5
Specify the encryption key lifetime—the number of seconds each security association should exist before expiring.
crypto ikev1 policy priority lifetime {seconds}
The range for a finite lifetime is 120 to 2147483647 seconds. Use 0 seconds for an infinite lifetime.
Example:
hostname(config)# crypto ikev1 policy 1 lifetime 43200
hostname(config)#




Step 6
Enable ISAKMP on the interface named outside.
crypto ikev1 enable interface-name
Example:
hostname(config)# crypto ikev1 enable outside
hostname(config)#



Step 7
Save the changes to the configuration.
write memory


Configure an Address Pool
The ASA requires a method for assigning IP addresses to users. This section uses address pools as an example.
Procedure


Create an address pool with a range of IP addresses, from which the ASA assigns addresses to the clients.
ip local pool poolname first-address—last-address [mask mask]
The address mask is optional. However, You must supply the mask value when the IP addresses assigned to VPN clients belong to a non-standard network and the data could be routed incorrectly if you use the default mask. A typical example is when the IP local pool contains 10.10.10.0/255.255.255.0 addresses, since this is a Class A network by default. This could cause routing issues when the VPN client needs to access different subnets within the 10 network over different interfaces.
Example:
hostname(config)# ip local pool testpool 192.168.0.10-192.168.0.15
hostname(config)#


Add a User
Procedure


Create a user, password, and privilege level.
username name {nopassword | password password [mschap | encrypted | nt-encrypted]}  [privilege priv_level]
Example:
Hostname(config)# username testuser password 12345678


Create an IKEv1 Transform Set or IKEv2 Proposal
This section shows how to configure a transform set (IKEv1) or proposal (IKEv2), which combines an encryption method and an authentication method.
The following steps show how to create both an IKEv1 and an IKEv2 proposal.
Procedure



Step 1
Configure an IKEv1 transform set that specifies the IPsec IKEv1 encryption and hash algorithms to be used to ensure data integrity.
crypto ipsec ikev1 transform-set transform-set-name encryption-method [authentication]
Use one of the following values for encryption:
·       esp-aes to use AES with a 128-bit key.
·       esp-aes-192 to use AES with a 192-bit key.
·       esp-aes-256 to use AES with a 256-bit key.
·       esp-des to use 56-bit DES-CBC.
·       esp-3des to use triple DES algorithm.
·       esp-null to not use encryption.
Use one of the following values for authentication:
·       esp-md5-hmac to use the MD5/HMAC-128 as the hash algorithm.
·       esp-sha-hmac to use the SHA/HMAC-160 as the hash algorithm.
·       esp-none to not use HMAC authentication.
Example:
To configure an IKEv1 transform set:
hostname(config)# crypto ipsec transform set FirstSet esp-3des esp-md5-hmac




Step 2
Configure an IKEv2 proposal set that specifies the IPsec IKEv2 protocol, encryption, and integrity algorithms to be used.
esp specifies the Encapsulating Security Payload (ESP) IPsec protocol (currently the only supported protocol for IPsec).
crypto ipsec ikev2 ipsec-proposal proposal_name
protocol {esp} {encryption {des | 3des | aes | aes-192 | aes-256 | null} | integrity {md5 | sha-1}
Use one of the following values for encryption:
·       des to use 56-bit DES-CBC encryption for ESP.
·       3des (default) to use the triple DES encryption algorithm for ESP.
·       aes to use AES with a 128-bit key encryption for ESP.
·       aes-192 to use AES with a 192-bit key encryption for ESP.
·       aes-256 to use AES with a 256-bit key encryption for ESP.
·       null to not use encryption for ESP.
Use one of the following values for integrity:
·       md5 specifies the md5 algorithm for the ESP integrity protection.
·       sha-1 (default) specifies the Secure Hash Algorithm (SHA) SHA-1, defined in the U.S. Federal Information Processing Standard (FIPS), for ESP integrity protection.
To configure an IKEv2 proposal:
hostname(config)# crypto ipsec ikev2 ipsec-proposal secure_proposal
hostname(config-ipsec-proposal)# protocol esp encryption des integrity md5


Define a Tunnel Group
A tunnel group is a collection of tunnel connection policies. You configure a tunnel group to identify AAA servers, specify connection parameters, and define a default group policy. The ASA stores tunnel groups internally.
There are two default tunnel groups in the ASA system: DefaultRAGroup, which is the default remote-access tunnel group, and DefaultL2Lgroup, which is the default LAN-to-LAN tunnel group. You can change these groups, but do not delete them. The ASA uses these groups to configure default tunnel parameters for remote access and LAN-to-LAN tunnel groups when there is no specific tunnel group identified during tunnel negotiation.
Procedure




Step 1
Create an IPsec remote access tunnel-group (also called connection profile).
tunnel-group name type type
Example:
hostname(config)# tunnel-group testgroup type ipsec-ra
hostname(config)#


Step 2
Enter tunnel group general attributes mode where you can enter an authentication method.
tunnel-group name general-attributes
Example:
hostname(config)# tunnel-group testgroup general-attributes
hostname(config-tunnel-general)#


Step 3
Specify an address pool to use for the tunnel group.
address-pool [(interface name)address_pool1 [...address_pool6]
Example:
hostname(config-general)# address-pool testpool


Step 4
Enter tunnel group ipsec attributes mode where you can enter IPsec-specific attributes for IKEv1 connections.
tunnel-group name ipsec-attributes
Example:
hostname(config)# tunnel-group testgroup ipsec-attributes
hostname(config-tunnel-ipsec)#


Step 5
(Optional) Configure a pre-shared key (IKEv1 only). The key can be an alphanumeric string from 1-128 characters.
The keys for the adaptive security appliance and the client must be identical. If a Cisco VPN Client with a different preshared key size tries to connect, the client logs an error message indicating it failed to authenticate the peer.
ikev1 pre-shared-key key
Example:
hostname(config-tunnel-ipsec)# pre-shared-key 44kkaol59636jnfx


Create a Dynamic Crypto Map
Dynamic crypto maps define policy templates in which not all the parameters are configured. This lets the ASA receive connections from peers that have unknown IP addresses, such as remote access clients.
Dynamic crypto map entries identify the transform set for the connection. You can also enable reverse routing, which lets the ASA learn routing information for connected clients, and advertise it via RIP or OSPF.
Perform the following task:
Procedure



Step 1
Create a dynamic crypto map and specifies an IKEv1 transform set or IKEv2 proposal for the map.
·       For IKEv1, use this command:
crypto dynamic-map dynamic-map-name seq-num set ikev1 transform-set transform-set-name
·       For IKEv2, use this command:
crypto dynamic-map dynamic-map-name seq-num set ikev2 ipsec-proposal proposal-name
Example:
hostname(config)# crypto dynamic-map dyn1 1 set ikev1 transform-set FirstSet
hostname(config)#
hostname(config)# crypto dynamic-map dyn1 1 set ikev2 ipsec-proposal secure_proposal
hostname(config)#


Step 2
(Optional) Enable Reverse Route Injection for any connection based on this crypto map entry.
crypto dynamic-map dynamic-map-name dynamic-seq-num set reverse-route
Example:
hostname(config)# crypto dynamic-map dyn1 1 set reverse route
hostname(config)#


Create a Crypto Map Entry to Use the Dynamic Crypto Map
Create a crypto map entry that lets the ASA use the dynamic crypto map to set the parameters of IPsec security associations.
In the following examples for this command, the name of the crypto map is mymap, the sequence number is 1, and the name of the dynamic crypto map is dyn1, which you created in the previous section.
Procedure



Step 1
Create a crypto map entry that uses a dynamic crypto map.
crypto map map-name seq-num ipsec-isakmp dynamic dynamic-map-name
Example:
hostname(config)# crypto map mymap 1 ipsec-isakmp dynamic dyn1


Step 2
Apply the crypto map to the outside interface.
crypto map map-name interface interface-name
Example:
hostname(config)# crypto map mymap interface outside


Step 3
Saves the changes to the configuration.
write memory


Configuring IPSec IKEv2 Remote Access VPN in Multi-Context Mode
For more information about configuring Remote Access IPsec VPNs, see the following sections:
·       Configure Interfaces
·       Add a User
·       Define a Tunnel Group
Configuration Examples for Remote Access IPsec VPNs
The following example shows how to configure a remote access IPsec/IKEv1 VPN:

hostname(config)# crypto ikev1 policy 10
hostname(config-ikev1-policy)# authentication pre-share
hostname(config-ikev1-policy)# encryption aes-256
hostname(config-ikev1-policy)# hash sha
hostname(config-ikev1-policy)# group 2
hostname(config)# crypto ikev1 enable outside
hostname(config)# ip local pool POOL 192.168.0.10-192.168.0.15
hostname(config)# username testuser password 12345678
hostname(config)# crypto ipsec ikev1 transform set AES256-SHA
esp-aes-256 esp-sha-hmac
hostname(config)# tunnel-group RAVPN type remote-access
hostname(config)# tunnel-group RAVPN general-attributes
hostname(config-general)# address-pool POOL
hostname(config)# tunnel-group RAVPN ipsec-attributes
hostname(config-ipsec)# ikev1 pre-shared-key ravpnkey
hostname(config)# crypto dynamic-map DYNMAP 1 set ikev1
transform-set AES256-SHA
hostname(config)# crypto dynamic-map DYNMAP 1 set reverse-route
hostname(config)# crypto map CMAP 1 ipsec-isakmp dynamic DYNMAP
hostname(config)# crypto map CMAP interface outside

The following example shows how to configure a remote access IPsec/IKEv2 VPN:

hostname(config)# crypto ikev2 policy 1
hostname(config-ikev2-policy)# group 2
hostname(config-ikev2-policy)# integrity sha512
hostname(config-ikev2-policy)# prf sha512
hostname(config)# crypto ikev2 enable outside
hostname(config)# ip local pool POOL 192.168.0.10-192.168.0.15
hostname(config)# username testuser password 12345678
hostname(config)# crypto ipsec ikev2 ipsec-proposal  AES256-SHA512
hostname(config-ipsec-proposal)# protocol esp encryption  aes-256
hostname(config-ipsec-proposal)# protocol esp integrity sha-512
hostname(config)# tunnel-group RAVPN type remote-access
hostname(config)# tunnel-group RAVPN general-attributes
hostname(config-general)# address-pool POOL
hostname(config)# tunnel-group RAVPN ipsec-attributes
hostname(config-tunnel-ipsec)# ikev2 local-authentication
pre-shared-key localravpnkey
hostname(config-tunnel-ipsec)# ikev2 remote-authentication
pre-shared-key remoteravpnkey
hostname(config)# crypto dynamic-map DYNMAP 1 set ikev2
ipsec-proposal AES256-SHA512
hostname(config)# crypto dynamic-map DYNMAP 1 set reverse-route
hostname(config)# crypto map CMAP 1 ipsec-isakmp dynamic DYNMAP
hostname(config)# crypto map CMAP interface outside



class default
  limit-resource All 0
  limit-resource Mac-addresses 65536
  limit-resource ASDM 5
  limit-resource SSH 5
  limit-resource Telnet 5
  limit-resource VPN AnyConnect 4.0%

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