![]() The tunnel will be in transport mode instead of VPN mode (default). In this example, we use 3DES encryption and SHA hashing. I arranged the configuration order so that it is the actual workflow- define a parameter, reference it in a modular configuration, apply the modular to global configuration.įirst define transform-set used in Phase 2. It is because later configuration are being referenced by earlier configuration in the CLI. You’ll see didn’t follow the logical order of configuring Phase 1, Phase 2. Step 3: Configure VPN Phase 1 and Phase 2 #DEBUG IPSEC VPN ASA ASDM PASSWORD#Ikev1 pre-shared-key ! - It is the group password for all VPN users Pre-shared-key ! - It is the group password for all VPN users Tunnel-group DefaultRAGroup ipsec-attributes Tunnel-group DefaultRAGroup ppp-attributes tunnel-group DefaultRAGroup general-attributesĪddress-pool VPNPOOL ! - VPN user will be assigned with an IP in the poolĭefault-group-policy SSLGROUPPOLICY ! - references the group-policy defined earlierĪuthentication-server-group LOCAL ! - user local authentication Next we define a “Tunnel Group” for the tunnel, You MUST use the default group with default name “DefaultRAGroup“ (the only exception is if you use certificate based authentication). Vpn-tunnel-protocol l2tp-ipsec ! - specifying the protocol being used group-policy SSLGROUPPOLICY internalĭns-server value 4.2.2.2 ! - can be your internal DNS servers or public DNS servers They are just a name, you can name them anything make sense in your environment. Note that I use all capital letters for variables being referenced in the command. Step 2: Create group-policy and tunnel-group The benefit is that you can do route summarization, ACL to cover this subnet easily and cleanly. For better security and flexible traffic control, I would put VPN users on their own subnet, and in a range that can be expressed by a subnet mask. If you put them on the same network, they would have access to everything on the same subnet. It is not a good idea to share a portion of your existing LAN subnet with VPN users. This address pool should not overlap with your existing network. Step 1: Configure a DHCP Pool for VPN users Save time by downloading the validated configuration scripts and have your VPN up in minutes. In this session, a step-by-step configuration tutorial is provided for both pre-8.3 and post-8.3 code. DHCP Pool for VPN users: 192.168.199.100 – 200Ĭonfiguring L2TP over IPSec VPN on Cisco ASA Configuration Example.You can configure RADIUS authentication to an AD. For simplicity, VPN user authentication is done locally on the ASA. We’ll also implement “split tunneling” so that regular Internet traffic is not sent through the tunnel. A DHCP pool is reserved on the ASA for VPN users. ![]() Remote VPN users connect to the Corp LAN using L2TP/IPSec VPN. Network TopologyĪ simple network is composed of a Corp LAN, a Cisco ASA acting as an Internet gateway and firewall. Next we’ll dive right into the configuration part. It is not the fastest VPN solution because of the double encapsulation overhead but you can’t really notice it running on the modem hardware. It checks data integrity and encapsulates the data twice. L2TP/IPsec provides data confidentiality, data integrity, and data authentication.įurthermore, L2TP/IPSec supports the highest encryption. It supports either computer certificates or a pre-shared key as the authentication method for IPsec. Unlike PPTP and SSTP, L2TP/IPsec enables machine authentication at the IPsec layer and user level authentication at the PPP layer. Since vulnerabilities have been found in 3DES algorithms, using 3DES is no longer recommended. AES-256 (Advanced Encryption Standard), AES-192, AES-128, and 3DES encryption algorithms. The IPSec authentication trailer provides message integrity check and authentication.ĭata encryption is done with one of the following protocols by using encryption keys generated from the IKE negotiation process. ![]() The outer layer adds IPSec ESP (Encapsulating Security Payload) header and trailer to the first layer. The inner layer comprised of an L2TP header and a UDP header wrapped around the PPP frame. L2TP has two layers of encapsulations – inner L2TP encapsulation and outer layer IPSec encapsulation. the encryption is done by IPSec in transport mode. Even the underlying tunneling technology still utilizes PPP specifications. L2TP combines the best features of PPTP and L2F. L2TP is a combination of PPTP and Layer 2 Forwarding (L2F), a technology developed by Cisco. ![]()
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