Tuesday, September 17, 2013

Cisco ASA Remote Access configuration for Mac OS X

I spent the day fighting to get a remote access IPSec connection set up as follows:

  • ASA 5515-X, running version 9.1.
  • ASA network interfaces are already configured.
  • IPSec clients are assigned addresses from the range
  • Client is running OS X 10.8.4 Mountain Lion.
  • Client is using the built-in OS X IPSec client.
  • Client IP is private, behind NAT, with a DHCP-assigned WAN IP.
  • After connecting, client should be able to reach the internal networks,
  • All other traffic is not sent across the VPN.
The following configuration should be added to the ASA:

ip local pool REMOTE_ACCESS_POOL
management-access inside
access-list REMOTE_ACCESS_SPLIT_TUNNEL remark The corporate network behind the ASA.
access-list REMOTE_ACCESS_SPLIT_TUNNEL standard permit 
access-list REMOTE_ACCESS_SPLIT_TUNNEL standard permit 
crypto ipsec ikev1 transform-set REMOTE_ACCESS_TS esp-aes-256 esp-sha-hmac 
crypto dynamic-map REMOTE_ACCESS_DYNMAP 1 set ikev1 transform-set REMOTE_ACCESS_TS
crypto map REMOTE_ACCESS_MAP 1 ipsec-isakmp dynamic REMOTE_ACCESS_DYNMAP
crypto map REMOTE_ACCESS_MAP interface outside
crypto ikev1 enable outside
crypto ikev1 policy 1
 authentication pre-share
 encryption aes-256
 hash sha
 group 2
 lifetime 7200
group-policy REMOTE_ACCESS_GP internal
group-policy REMOTE_ACCESS_GP attributes
 split-tunnel-policy tunnelspecified
 split-tunnel-network-list value REMOTE_ACCESS_SPLIT_TUNNEL
username hunter password **** encrypted
tunnel-group REMOTE_ACCESS_TUNNELGRP type remote-access
tunnel-group REMOTE_ACCESS_TUNNELGRP general-attributes
 address-pool REMOTE_ACCESS_POOL
 default-group-policy REMOTE_ACCESS_GP
tunnel-group REMOTE_ACCESS_TUNNELGRP ipsec-attributes
 ikev1 pre-shared-key *****

For explanation of what all this does, I recommend reading the following Cisco docs. It is worth noting that this configuration does not work with Windows 7/8, which use IKEv2 instead of v1.

The configuration for the built-in OS X IPSec client is described in the following doc. One gotcha I ran into (which is clearly stated in the document) is that the tunnel-group name must be specified in the 'Group Name' field on the Mac. In the case of the above configuration, the group name is REMOTE_ACCESS_TUNNELGRP.

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