Cisco VPN – Split Tunnel Not Working?

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KB ID 0001239 Dtd 19/09/16

Problem

Here I'm dealing with AnyConnect VPNs, but the principles are exactly the same for both remote IPSEC and L2TP VPNs. You connect to your VPN and can no longer browse the internet from your remote location. 

You can confirm that split-tunnelling is working or not by connecting with your VPN client and looking at the routing information.

Check Split Tunnel AnyConnect

Solution

Before proceeding are you sure Split-Tunnelling has ever been setup and configured? See the following article.

Cisco ASA – Enable Split Tunnel for IPSEC / SSLVPN / AnyConnect Clients

For Split Tunnelling to work you need;

  • An Access Control List, allowing the networks/IP's that are protected by your ASA, that you need to access over the VPN.
  • A Group-policy that references the access-list above.
  • A Tunnel Group that references the Group-policy above.

The lines get a bit blurred if you are in the ASDM, in there the terminology, is access control list, group-policy, and connection profile.

Troubleshoot Split Tunnel From CLI

Connect and authenticate an AnyConnect client. Then on the firewall run the following command.

Petes-ASA# show vpn-sessiondb anyconnect

Session Type: AnyConnect

Username     : petelong               Index        : 4
Assigned IP  : 172.16.1.1             Public IP    : 192.168.100.77
Protocol     : AnyConnect-Parent SSL-Tunnel DTLS-Tunnel
License      : AnyConnect Premium
Encryption   : AnyConnect-Parent: (1)none  SSL-Tunnel: (1)AES256  DTLS-Tunnel: (1)AES256
Hashing      : AnyConnect-Parent: (1)none  SSL-Tunnel: (1)SHA1  DTLS-Tunnel: (1)SHA1
Bytes Tx     : 14128                  Bytes Rx     : 12305
Group Policy : GroupPolicy_ANYCONNECT-PROFILE
Tunnel Group : ANYCONNECT-PROFILE
Login Time   : 12:49:31 GMT/BST Mon Sep 19 2016
Duration     : 0h:01m:03s
Inactivity   : 0h:00m:00s
VLAN Mapping : N/A                    VLAN         : none
Audt Sess ID : c0a86e010000400057dfd0cb
Security Grp : none

Petes-ASA#

From the output above, we know the name of the Group Policy and the Tunnel Group. The fact we can see BOTH is an indication that the tunnel group is setup correctly, but it does no harm to check.

Petes-ASA# show run tunnel-group ANYCONNECT-PROFILE
tunnel-group ANYCONNECT-PROFILE type remote-access
tunnel-group ANYCONNECT-PROFILE general-attributes
 address-pool ANYCONNECT-POOL
 default-group-policy GroupPolicy_ANYCONNECT-PROFILE
tunnel-group ANYCONNECT-PROFILE webvpn-attributes
 group-alias ANYCONNECT-PROFILE enable
Petes-ASA#

Then check that that group-policy has enabled split tunnelling, and referenced the correct access control list.

Petes-ASA# show run group-policy  GroupPolicy_ANYCONNECT-PROFILE
group-policy GroupPolicy_ANYCONNECT-PROFILE internal
group-policy GroupPolicy_ANYCONNECT-PROFILE attributes
 wins-server none
 dns-server value 8.8.8.8 8.8.4.4
 vpn-tunnel-protocol ssl-client
 split-tunnel-policy tunnelspecified
 split-tunnel-network-list value SPLIT-TUNNEL
 default-domain value petenetlive.com
 webvpn
  anyconnect profiles value testbench type user
Petes-ASA#

Finally take the ACL name (SPLIT-TUNNEL) and make sure that's OK.

Petes-ASA# show run access-list SPLIT-TUNNEL
access-list SPLIT-TUNNEL standard permit 192.168.110.0 255.255.255.0
access-list SPLIT-TUNNEL standard permit 192.168.115.0 255.255.255.0

Troubleshoot Split Tunnel From ASDM

As above connect a remote AnyConnect client > Monitoring > VPN > VPN Statistics > Sessions > AnyConnect Client > Select your connected client > Details.

ASDM View AnyConnect Connections

Note: The info we actually want, is shown on this screen, but let's look at the session anyway.

Now you can see the Group Policy and Connection Profile thats been applied to this user.

View AnyConnect Connection profiles

Configuration > Remote Access VPN > AnyConnect Connection Profiles > Select the one shown above > Edit.

AnyConnect Split-Tunnel Profiles

Check the Group-Policy is correct, (Note: You can manage it directly from here, but I will take the long way round).

AnyConnect Group-Policy

Configuration > Remote Access VPN > Network (Client Access) > Group Policies > Select the one shown above > Edit.

ASDM AnyConnect Group-Policy Split-Tunnel

Advanced > Split Tunneling > Ensure Policy is 'untucked' and set to 'Tunnel Network List Below' > Ensure Network list is 'untucked' and set to the name of your split tunnel ACL > Manage.

ASDM Apply Split-Tunnel Policy

Make sure the network(s) or IP addresses behind your ASA, that you want to access over the VPN, are listed.

ASDM Split-Tunnel ACL

 

Related Articles, References, Credits, or External Links

Cisco ASA – Enable Split Tunnel for IPSEC / SSLVPN / AnyConnect Clients

Cisco ASA – Remote VPN Client Internet Access

Author: PeteLong

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