AnyConnect: Allow ‘Local’ LAN Access

KB ID 0001689

Problem

Note: This WONT WORK if you ‘force-tunnel’ or ‘tunnel-all’ remote VPN traffic, (if you are unsure Google ‘what’s my ip’ > Take note of it > Connect to AnyConnect and repeat the procedure, if your public IP address has changed to the IP address of the ASA then you force-tunnel/tunnel-all traffic).

With more people remote working now, I’m getting a lot more questions about RA-VPN and particularly AnyConnect. By default when connecting to any Cisco remote access VPN, it pretty much stops you connecting to anything outside the VPN tunnel, (unless you enable Split Tunnelling). This includes stopping you talking to assets on your remote network also.

This is basically ‘Good practice’, as a corporate entity you have authenticated a remote machine NOT the entire network it is on! But what happens when your MD want to print a work document on his/her home printer? Or you have a NAS drive at home with documents on it you can access while connected to the VPN?

AnyConnect-Local-LAN-Access

Well, then you can ‘make a judgement call’ to whether or not you want to enable ‘Local LAN Access’ for your remote clients.

Full Disclosure: While this does not let everything on the remote clients LAN connect to the corporate network. If another client on a remote network was infected and compromised, and it proliferated its infection via the LAN,  (to your authenticated remote client), then that client could infect the corporate network. This is what’s known as a ‘pivot attack’.

Solution

Assuming you are happy to enable local LAN access its a TWO STEP procedure. Firstly you enable Local LAN Access on the AnyConnect Client Profile, then you enable split tunnelling and allow all networks, (because you don’t know what all the remote network addresses may be). 

Step 1: Add Local LAN Access to the AnyConnect Client Profile

If you are unfamiliar with ‘AnyConnect Client profiles’, they are simply XML files that are applied to to an AnyConnect Connection Profile, I already have one so I just need to edit it, And tick ‘Local LAN Access’.

AnyConnect Alow LAN Access

What If you Don’t Already Have One? Not a problem. In the ASDM > Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Client Profile > Add > Give it a name > Set the Group Policy to your AnyConnect Group Policy > OK > Apply > Edit.

What Does User Controllable Mean? It means your users can enable or disable it, (see below.) If you untick this then they wont have that option.

AnyConnect Alow LAN Access User Controllable

Step 2: Add 0.0.0.0/32 to Split Tunnelling

You configure split tunnelling in your AnyConnect Group-Policy (ASDM > Configuration > Remote Access VPN > Network (Client) Access > Group Policies) Locate yours and edit it, navigate to Advanced > Split Tunnelling > Policy: Untick inherit, and set to Exclude Network List Below > Network List: Untick Inherit and click Manage.

Firstly: Create an ACL and call it “ACL-Local-LAN-Access’ > OK

Secondly: Select the ACL you just created and add an ACE to it > permit 0.0.0.0/32 > OK > OK > OK > Apply > File > Save Running Configuration to Flash.

Your remote workers will need to disconnect and reconnect before it will take effect. In some cases with older clients they need to reboot, (or have the AnyConnect service stopped  and restarted.) If you experience problems make sure your clients have got the new XML file with;

<LocalLanAccess UserControllable="true">true</LocalLanAccess>

inside it, to find out where those files are stored see THIS POST.

Related Articles, References, Credits, or External Links

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Author: PeteLong

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