Cato IPsec Guide: IKEv1 vs IKEv2

IPsec Site Best Practices - Migrating to IKEv2

In general, Cato recommends that you use IPsec IKEv2 sites as a best practice. Some of the improvements with IKEv2 are listed below:

  1. IKEv2 increases efficiency by reducing the number of messages that must be exchanged to setup a VPN tunnel. Tunnels are setup faster and with less bandwidth.

  2. IKEv2 is more reliable. There’s a built-in liveness check in IKEv2 to detect when the tunnel goes down.

  3. IKEv2 protects against DoS attacks. Unlike in IKEv1, an IKEv2 responder doesn’t have to perform significant processing until the initiator proves it can receive messages at its advertised IP address.

  4. NAT-T is built-in. NAT-T, or NAT Traversal, is required when a VPN endpoint resides behind a router that performs NAT. IPsec tunnels send data using the Encapsulating Security Payload (ESP) which is not compatible with NAT. Therefore, NAT-T is used to encapsulate the ESP packets in UDP which can then be routed over NAT.

For more information on the benefits of using use IPsec IKEv2 sites, see RFC 4306.

Similarities Between IKEv2 and IKEv1

Below is a comparison of strongSwan configurations for IKEv1 and IKEv2 tunnels. strongSwan is an open-source IPsec solution for multiple operating systems, including Windows and macOS.

IKEv1

IKEv2

 
conn cato-vpn
        auto=add
        compress=no
        type=tunnel
        keyexchange=ikev1
        fragmentation=yes
        forceencaps=yes
        ike=aes256-sha1-modp1024
        esp=aes256-sha1
        dpdaction=clear
        dpddelay=300s
        rekey=no
        left=172.16.1.62
        leftid=54.183.180.107
        leftsubnet=172.16.1.0/24
        right=45.62.177.115
        rightid=45.62.177.115
        rightsubnet=172.17.3.0/24
        authby=secret
 
conn cato-vpn
        auto=add
        compress=no
        type=tunnel
        keyexchange=ikev2
        fragmentation=yes
        forceencaps=yes
        ike=aes256-sha1-modp1024
        esp=aes256-sha1
        dpdaction=clear
        dpddelay=300s
        rekey=no
        left=172.16.1.62
        leftid=54.183.180.107
        leftsubnet=172.16.1.0/24
        right=45.62.177.115
        rightid=45.62.177.115
        rightsubnet=172.17.3.0/24
        authby=secret

The only difference is a single number. Changing the keyexchange value from ikev1 to ikev2 is enough to convert strongSwan from IKEv1 to IKEv2.

Note: You may set the IPSec shared secret (PSK) up to 64 characters for both IKEv1 and IKEv2 sites.

Switching from IKEv1 to IKEv2 in the Cato Management Application

The steps required to migrate from an IKEv1 to IKEv2 tunnel are listed below.

To migrate a site from an IKEv1 to IKEv2 tunnel:

  1. On the Network > Sites screen, select the site you want switch from IKEv1 to IKEv2.

  2. On the Network > Sites > [site name] > Site Configuration > General screen, in the Connection Type dropdown, select IPsec IKEv2. The site's Native Range and other networks are lost when you change the Connection Type.

    360002841277-image-0.png

  3. On the Network > Sites > [site name] > Site Configuration > Networks screen, enter the Native Range and any other remote networks. These are the remote traffic selectors.

  4. On the Network > Sites > [site name] > Site Configuration > IPsec screen, under the Primary section, select the Cato IP (Egress) IP and enter the Site IP of the remote VPN gateway.

    360002920918-image-1.png

  5. Enter the PSK in the Password field under Primary PSK.

    360002841297-image-2.png

  6. Expand the Routing section, add the routing option for the site under Network Ranges. These should all be networks already configured at other sites connected to Cato or the Cato VPN range.

    360002841317-image-3.png

  7. Select the Initiate connection by Cato checkbox so Cato initiates the VPN connection. This configuration is optional but recommended because the remote VPN gateway may not be configured to initiate the connection.

  8. (Optional) Expand the Init Message Parameters section, and configure the settings. As most IPsec IKEv2-supporting solutions implement automatic negotiation of the following Init and Auth parameters, Cato recommends setting them to Automatic unless specifically instructed to by your firewall vendor.

    You might have noticed that the Init and Auth message parameters are almost identical to the Phase 1 and Phase 2 parameters in IKEv1, but there is both a PRF and Integrity algorithm configuration option in IKEv2. Most vendors do not support different PRF and integrity algorithms, so if in doubt, set them to Automatic or make sure that they’re set to the same value.

  9. Click Save.

IKEv2: The Final Frontier

These days, there is really only one reason to party like it’s 1999, or to be precise, 1998, when IKEv1 was first defined by the IETF: if at least one side of the VPN connection is terminating on a legacy device that only supports IKEv1. The major cloud providers (AWS, GCP, Azure, Alibaba Cloud) support IKEv2. So, unless you are connecting to an older VPN endpoint, IKEv2 should be your first choice when setting up VPN tunnels.

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