Cisco Systems ASA5515K9, ASA 5500 Differences in Client Split Tunneling Behavior for Traffic within the Subnet, Setting the Split-Tunneling Policy, Creating a Network List for Split-Tunneling

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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter67 Configuring Connection Profiles, Group Policies, and Users
Group Policies
Differences in Client Split Tunneling Behavior for Traffic within the Subnet
The AnyConnect client and the legacy Cisco VPN client (the IPsec/IKEv1 client) behave differently
when passing traffic to sites within the same subnet as the IP address assigned by the ASA. With
AnyConnect, the client passes traffic to all sites specified in the split tunneling policy you configured,
and to all sites that fall within the same subnet as the IP address assigned by the ASA. For example, if
the IP address assigned by the ASA is 10.1.1.1 with a mask of 255.0.0.0, the endpoint device passes all
traffic destined to 10.0.0.0/8, regardless of the split tunneling policy.
By contrast, the legacy Cisco VPN client only passes traffic to addresses specified by the split-tunneling
policy, regardless of the subnet assigned to the client.
Therefore, use a netmask for the assigned IP address that properly references the expected local subnet.
Setting the Split-Tunneling Policy
Set the rules for tunneling traffic by specifying the split-tunneling policy:
hostname(config-group-policy)# split-tunnel-policy {tunnelall | tunnelspecified |
excludespecified}
hostname(config-group-policy)# no split-tunnel-policy
The default is to tunnel all traffic. To set a split tunneling policy, enter the split-tunnel-policy command
in group-policy configuration mode. To remove the split-tunnel-policy attribute from the running
configuration, enter the no form of this command. This enables inheritance of a value for split tunneling
from another group policy.
The excludespecified keyword defines a list of networks to which traffic goes in the clear. This feature
is useful for remote users who want to access devices on their local network, such as printers, while they
are connected to the corporate network through a tunnel. This option applies only to the Cisco VPN
client.
The tunnelall keyword specifies that no traffic goes in the clear or to any other destination than the ASA.
This, in effect, disables split tunneling. Remote users reach Internet networks through the corporate
network and do not have access to local networks. This is the default option.
The tunnelspecified keyword tunnels all traffic from or to the specified networks. This option enables
split tunneling. It lets you create a network list of addresses to tunnel. Data to all other addresses travels
in the clear and is routed by the remote user’s Internet service provider.
Note Split tunneling is primarily a traffic management feature, not a security feature. For optimum security,
we recommend that you do not enable split tunneling.
The following example shows how to set a split tunneling policy of tunneling only specified networks
for the group policy named FirstGroup:
hostname(config)# group-policy FirstGroup attributes
hostname(config-group-policy)# split-tunnel-policy tunnelspecified
Creating a Network List for Split-Tunneling
Create a network list for split tunneling using the split-tunnel-network-list command in group-policy
configuration mode.
hostname(config-group-policy)# split-tunnel-network-list {value access-list_name | none}
hostname(config-group-policy)# no split-tunnel-network-list value [access-list_name]