Phase 2 parameters

This section describes the Phase 2 parameters that are required to establish communication through a VPN.

The following topics are included in this section:

Phase 2 settings

Configuring the Phase 2 parameters

Phase 2 settings

After IPsec VPN Phase 1 negotiations complete successfully, Phase 2 negotiation begins. Phase 2 parameters define the algorithms that the FortiGate unit can use to encrypt and transfer data for the remainder of the session. The basic Phase 2 settings associate IPsec Phase 2 parameters with a Phase 1 configuration.

When defining Phase 2 parameters, you can choose any set of Phase 1 parameters to set up a secure connection and authenticate the remote peer.

For more information on Phase 2 settings in the web-based manager, see IPsec VPN in the web-based manager on page 32.

The information and procedures in this section do not apply to VPN peers that perform negotiations using manual keys.

Phase 2 proposals

In Phase 2, the VPN peer or client and the FortiGate unit exchange keys again to establish a secure communication channel. The Phase 2 Proposal parameters select the encryption and authentication algorithms needed to generate keys for protecting the implementation details of Security Associations (SAs). The keys are generated automatically using a Diffie-Hellman algorithm.

Replay detection

IPsec tunnels can be vulnerable to replay attacks. Replay Detection enables the FortiGate unit to check all IPsec packets to see if they have been received before. If any encrypted packets arrive out of order, the FortiGate unit discards them.

IKE/IPsec Extended Sequence Number (ESN) support

64-bit Extended Sequence numbers (as described in RFC 4303, RFC 4304 as an addition to IKEv1, and RFC 5996 for IKEv2.) are supported for IPsec when Replay Detection is enabled.

Perfect Forward Secrecy (PFS)

By default, Phase 2 keys are derived from the session key created in Phase 1. Perfect Forward Secrecy (PFS) forces a new Diffie-Hellman exchange when the tunnel starts and whenever the Phase 2 keylife expires, causing a new key to be generated each time. This exchange ensures that the keys created in Phase 2 are unrelated to the Phase 1 keys or any other keys generated automatically in Phase 2.

Phase 2 settings

Keylife

The Keylife setting sets a limit on the length of time that a Phase 2 key can be used. The default units are seconds. Alternatively, you can set a limit on the number of kilobytes (KB) of processed data, or both. If you select both, the key expires when either the time has passed or the number of KB have been processed. When the Phase 2 key expires, a new key is generated without interrupting service.

Quick mode selectors

Quick mode selectors determine which IP addresses can perform IKE negotiations to establish a tunnel. By only allowing authorized IP addresses access to the VPN tunnel, the network is more secure.

The default settings are as broad as possible: any IP address or configured address object, using any protocol, on any port.

While the drop down menus for specifying an address also show address groups, the use of address groups may not be supported on a remote endpoint device that is not a FortiGate.

The address groups are at the bottom of the list to make it easy to distinguish between addresses and address groups.

When configuring Quick Mode selector Source address and Destination address, valid options include IPv4 and IPv6 single addresses, IPv4 subnet, or IPv6 subnet. For more information on IPv6 IPsec VPN, see Overview of IPv6 IPsec support on page 1.

There are some configurations that require specific selectors:

• The VPN peer is a third-party device that uses specific phase2 selectors.
• The FortiGate unit connects as a dialup client to another FortiGate unit, in which case (usually) you must specify a source IP address, IP address range, or subnet. However, this is not required if you are using dynamic routing and mode-cfg.

With FortiOS VPNs, your network has multiple layers of security, with quick mode selectors being an important line of defence.

• Routes guide traffic from one IP address to another.
• Phase 1 and Phase 2 connection settings ensure there is a valid remote end point for the VPN tunnel that agrees on the encryption and parameters.
• Quick mode selectors allow IKE negotiations only for allowed peers. l Security policies control which IP addresses can connect to the VPN. l Security policies also control what protocols are allowed over the VPN along with any bandwidth limiting.

FortiOS is limited with IKEv2 selector matching. When using IKEv2 with a named traffic selector, no more than 32 subnets per traffic selector are added, since FortiOS doesn’t fully implement the IKEv2 selector matching rules.

The workaround is to use multiple Phase 2s. If the configuration is FGT <-> FGT, then the better alternative is to just use 0.0.0.0 <-> 0.0.0.0 and use the firewall policy for enforcement.

 

Using the add-route option

Consider using the add-route option to add a route to a peer destination selector. Phase 2 includes the option of allowing the add-route to automatically match the settings in Phase 1. For more information, refer to Phase 1 parameters on page 46.

Syntax

Phase 2

config vpn ipsec {phase2 | phase2-interface} edit <name> set add-route {phase1 | enable | disable}

end

end

Configuring the Phase 2 parameters

If you are creating a hub-and-spoke configuration or an Internet-browsing configuration, you may have already started defining some of the required Phase 2 parameters. If so, edit the existing definition to complete the configuration.

Specifying the Phase 2 parameters

1. Go to VPN > IPsec Tunnels and create the new custom tunnel or edit an existing tunnel.
2. Open the Phase 2 Selectors panel (if it is not available, you may need to click the Convert to Custom Tunnel button).
3. Enter a Name for the Phase 2 configuration, and select a Phase 1 configuration from the drop-down list.
4. Select Advanced.
5. Include the appropriate entries as follows:

Phase 2 Proposal

Select the encryption and authentication algorithms that will be used to change data into encrypted code. Add or delete encryption and authentication algorithms as required. Select a minimum of one and a maximum of three combinations. The remote peer must be configured to use at least one of the proposals that you define. It is invalid to set both Encryption and Authentication to null.

 

Encryption	Select a symmetric-key algorithms: NULL — Do not use an encryption algorithm. DES — Digital Encryption Standard, a 64-bit block algorithm that uses a 56-bit key. 3DES — Triple-DES; plain text is encrypted three times by three keys. AES128 — A 128-bit block algorithm that uses a 128-bit key. AES192 — A 128-bit block algorithm that uses a 192-bit key. AES256 — A 128-bit block algorithm that uses a 256-bit key. ChaCha20/Poly1305— A 128-bit block algorithm that uses a 128-bit key and a symmetric cipher. Only available for IKEv2.
Authentication	You can select either of the following message digests to check the authenticity of messages during an encrypted session: NULL — Do not use a message digest. MD5 — Message Digest 5. SHA1 — Secure Hash Algorithm 1 – a 160-bit message digest. To specify one combination only, set the Encryption and Authentication options of the second combination to NULL. To specify a third combination, use the Add button beside the fields for the second combination. For information regarding NP accelerated offloading of IPsec VPN authentication algorithms, please refer to the Hardware Acceleration handbook chapter.
Enable replay detection	Optionally enable or disable replay detection. Replay attacks occur when an unauthorized party intercepts a series of IPsec packets and replays them back into the tunnel.
Enable perfect forward secrecy (PFS)	Enable or disable PFS. Perfect forward secrecy (PFS) improves security by forcing a new Diffie-Hellman exchange whenever keylife expires.
Diffie-Hellman Group	Select one Diffie-Hellman group (1, 2, 5, 14 through 21, or 27 through 30). The remote peer or dialup client must be configured to use the same group.
Keylife	Select the method for determining when the Phase 2 key expires: Seconds, KBytes, or Both. If you select Both, the key expires when either the time has passed or the number of KB have been processed. The range is from 120 to 172800 seconds, or from 5120 to 2147483648 KB.
Autokey Keep Alive	Enable the option if you want the tunnel to remain active when no data is being processed.
Auto-negotiate	Enable the option if you want the tunnel to be automatically renegotiated when the tunnel expires.

 

DHCP-IPsec

Select Enable if the FortiGate unit acts as a dialup server and FortiGate DHCP server or relay will be used to assign VIP addresses to FortiClient dialup clients. The DHCP server or relay parameters must be configured separately. If the FortiGate unit acts as a dialup server and the FortiClient dialup client VIP addresses match the network behind the dialup server, select Enable to cause the FortiGate unit to act as a proxy for the dialup clients. This is available only for Phase 2 configurations associated with a dialup Phase 1 configuration. It works only on policy-based VPNs.

Autokey Keep Alive

The Phase 2 SA has a fixed duration. If there is traffic on the VPN as the SA nears expiry, a new SA is negotiated and the VPN switches to the new SA without interruption. If there is no traffic, however, the SA expires (by default) and the VPN tunnel goes down. A new SA will not be generated until there is traffic.

The Autokey Keep Alive option ensures that a new Phase 2 SA is negotiated, even if there is no traffic, so that the VPN tunnel stays up.

Auto-negotiate

By default, the Phase 2 security association (SA) is not negotiated until a peer attempts to send data. The triggering packet and some subsequent packets are dropped until the SA is established. Applications normally resend this data, so there is no loss, but there might be a noticeable delay in response to the user.

If the tunnel goes down, the auto-negotiate feature (when enabled) attempts to re-establish the tunnel. Autonegotiate initiates the Phase 2 SA negotiation automatically, repeating every five seconds until the SA is established.

Automatically establishing the SA can be important for a dialup peer. It ensures that the VPN tunnel is available for peers at the server end to initiate traffic to the dialup peer. Otherwise, the VPN tunnel does not exist until the dialup peer initiates traffic.

The auto-negotiate feature is available through the Command Line Interface (CLI) via the following commands:

config vpn ipsec phase2 edit <phase2_name> set auto-negotiate enable

end

Installing dynamic selectors via auto-negotiate

The IPsec SA connect message generated is used to install dynamic selectors. These selectors can now be installed via the auto-negotiate mechanism. When phase 2 has auto-negotiate enabled, and phase 1 has meshselector-type set to subnet, a new dynamic selector will be installed for each combination of source and destination subnets. Each dynamic selector will inherit the auto-negotiate option from the template selector and begin SA negotiation. Phase 2 selector sources from dial-up clients will all establish SAs without traffic being initiated from the client subnets to the hub.

DHCP-IPsec

Select this option if the FortiGate unit assigns VIP addresses to FortiClient dialup clients through a DHCP server or relay. This option is available only if the Remote Gateway in the Phase 1 configuration is set to Dialup User and it works only on policy-based VPNs.

With the DHCP-IPsec option, the FortiGate dialup server acts as a proxy for FortiClient dialup clients that have VIP addresses on the subnet of the private network behind the FortiGate unit. In this case, the FortiGate dialup server acts as a proxy on the local private network for the FortiClient dialup client. A host on the network behind the dialup server issues an ARP request, corresponding to the device MAC address of the FortiClient host (when a remote server sends an ARP to the local FortiClient dialup client). The FortiGate unit then answers the ARP request on behalf of the FortiClient host, and forwards the associated traffic to the FortiClient host through the tunnel.

Acting as a proxy prevents the VIP address assigned to the FortiClient dialup client from causing possible ARP broadcast problems — the normal and VIP addresses can confuse some network switches by two addresses having the same MAC address.

IPsec support for ChaCha20/Poly1305 AEAD cipher

In IKEv2, to support RFC 7634, crypto algorithms ChaCha20 and Poly1305 can be used together as a combined mode AEAD cipher (like aes-gcm) in the new crypto_ftnt cipher in cipher_chacha20poly1305.c.

Syntax

config vpn ipsec phase2-interface edit <name> set phase1name <name> set proposal chacha20poly1305

next

end

IPsec support for AES-GCM for IKEv2 Phase 1

In IKEv2, to support RFC 5282, AEAD algorithm AES-GCM is now supported, both 128 and 256-bit variants.

Syntax

config vpn ipsec phase2-interface edit <name> set phase1name <name> set proposal [aes128gcm | aes256gcm]

next end

 

Phase 1 parameters

This chapter provides detailed step-by-step procedures for configuring a FortiGate unit to accept a connection from a remote peer or dialup client. The Phase 1 parameters identify the remote peer or clients and supports authentication through preshared keys or digital certificates. You can increase access security further using peer identifiers, certificate distinguished names, group names, or the FortiGate extended authentication (XAuth) option for authentication purposes.

The information and procedures in this section do not apply to VPN peers that perform negotiations using manual keys.

The following topics are included in this section:

Overview

Defining the tunnel ends

Choosing Main mode or Aggressive mode

Choosing the IKE version

Authenticating the FortiGate unit

Authenticating remote peers and clients

Defining IKE negotiation parameters

Using XAuth authentication

Dynamic IPsec route control

Overview

To configure IPsec Phase 1 settings, go to VPN > IPsec Tunnels and edit the Phase 1 Proposal (if it is not available, you may need to click the Convert to Custom Tunnel button).

IPsec Phase 1 settings define:

• The remote and local ends of the IPsec tunnel l If Phase 1 parameters are exchanged in multiple rounds with encrypted authentication information (main mode) or in a single message with authentication information that is not encrypted (aggressive mode)
• If a preshared key or digital certificates will be used to authenticate the FortiGate unit to the VPN peer or dialup client
• If the VPN peer or dialup client is required to authenticate to the FortiGate unit. A remote peer or dialup client can authenticate by peer ID or, if the FortiGate unit authenticates by certificate, it can authenticate by peer certificate. l The IKE negotiation proposals for encryption and authentication
• Optional XAuth authentication, which requires the remote user to enter a user name and password. A FortiGate VPN server can act as an XAuth server to authenticate dialup users. A FortiGate unit that is a dialup client can also be configured as an XAuth client to authenticate itself to the VPN server.

For all the Phase 1 web-based manager fields, see IPsec VPN in the web-based manager on page 32.

 

Defining the tunnel ends

To begin defining the Phase 1 configuration, go to VPN > IPsec Tunnels and select Create New. Enter a unique descriptive name for the VPN tunnel and follow the instructions in the VPN Creation Wizard.

The Phase 1 configuration mainly defines the ends of the IPsec tunnel. The remote end is the remote gateway with which the FortiGate unit exchanges IPsec packets. The local end is the FortiGate interface that sends and receives IPsec packets.

The remote gateway can be:

l A static IP address l A domain name with a dynamic IP address l A dialup client

A statically addressed remote gateway is the simplest to configure. You specify the IP address. Unless restricted in the security policy, either the remote peer or a peer on the network behind the FortiGate unit can bring up the tunnel.

If the remote peer has a domain name and subscribes to a dynamic DNS service, you need to specify only the domain name. The FortiGate unit performs a DNS query to determine the appropriate IP address. Unless restricted in the security policy, either the remote peer or a peer on the network behind the FortiGate unit can bring up the tunnel.

If the remote peer is a dialup client, only the dialup client can bring up the tunnel. The IP address of the client is not known until it connects to the FortiGate unit. This configuration is a typical way to provide a VPN for client PCs running VPN client software such as the FortiClient Endpoint Security application.

The local end of the VPN tunnel, the Local Interface, is the FortiGate interface that sends and receives the IPsec packets. This is usually the public interface of the FortiGate unit that is connected to the Internet (typically the WAN1 port). Packets from this interface pass to the private network through a security policy.

By default, the local VPN gateway is the IP address of the selected Local Interface. If you are configuring an interface mode VPN, you can optionally use a secondary IP address of the Local Interface as the local gateway.

Choosing Main mode or Aggressive mode

The FortiGate unit and the remote peer or dialup client exchange Phase 1 parameters in either Main mode or Aggressive mode. This choice does not apply if you use IKE version 2, which is available only for route-based configurations.

l In Main mode, the Phase 1 parameters are exchanged in multiple rounds with encrypted authentication information l In Aggressive mode, the Phase 1 parameters are exchanged in a single message with unencrypted authentication information.

Although Main mode is more secure, you must select Aggressive mode if there is more than one dialup Phase 1 configuration for the interface IP address, and the remote VPN peer or client is authenticated using an identifier local ID. Aggressive mode might not be as secure as Main mode, but the advantage to Aggressive mode is that it Choosing the IKE version

is faster than Main mode (since fewer packets are exchanged). Aggressive mode is typically used for remote access VPNs. But you would also use aggressive mode if one or both peers have dynamic external IP addresses. Descriptions of the peer options in this guide indicate whether Main or Aggressive mode is required.

IPsec VPN in the web-based manager

To configure an IPsec VPN, use the general procedure below. With these steps, your FortiGate unit will automatically generate unique IPsec encryption and authentication keys. If a remote VPN peer or client requires a specific IPsec encryption or authentication key, you must configure your FortiGate unit to use manual keys instead.

1. Define Phase 1 parameters to authenticate remote peers and clients for a secure connection. See IPsec VPN in the web-based manager on page 32.
2. Define Phase 2 parameters to create a VPN tunnel with a remote peer or dialup client. See IPsec VPN in the webbased manager on page 32.
3. Create a security policy to permit communication between your private network and the VPN. Policy-based VPNs have an action of IPSEC, where for interface-based VPNs the security policy action is ACCEPT. See Defining VPN security policies on page 1.

The FortiGate unit implements the Encapsulated Security Payload (ESP) protocol. Internet Key Exchange (IKE) is performed automatically based on pre-shared keys or X.509 digital certificates. Interface mode, supported in NAT mode only, creates a virtual interface for the local end of a VPN tunnel.

This chapter contains the following sections:

Phase 1 configuration

Phase 2 configuration

Concentrator

IPsec Monitor

Phase 1 configuration

To begin defining the Phase 1 configuration, go to VPN > IPsec Tunnels and select Create New. Enter a unique descriptive name for the VPN tunnel and follow the instructions in the VPN Creation Wizard.

The Phase 1 configuration mainly defines the ends of the IPsec tunnel. The remote end is the remote gateway with which the FortiGate unit exchanges IPsec packets. The local end is the FortiGate interface that sends and receives IPsec packets.

If you want to control how the IKE negotiation is processed when there is no traffic, as well as the length of time the FortiGate unit waits for negotiations to occur, you can use the negotiation-timeout and autonegotiate commands in the CLI.

Name	Type a name for the Phase 1 definition. The maximum name length is 15 characters for an interface mode VPN, 35 characters for a policy-based VPN. If Remote Gateway is Dialup User, the maximum name length is further reduced depending on the number of dialup tunnels that can be established: by 2 for up to 9 tunnels, by 3 for up to 99 tunnels, 4 for up to 999 tunnels, and so on. For a tunnel mode VPN, the name normally reflects where the remote connection originates. For a route-based tunnel, the FortiGate unit also uses the name for the virtual IPsec interface that it creates automatically.
Remote Gateway	Select the category of the remote connection: Static IP Address — If the remote peer has a static IP address. Dialup User — If one or more FortiClient or FortiGate dialup clients with dynamic IP addresses will connect to the FortiGate unit. Dynamic DNS — If a remote peer that has a domain name and subscribes to a dynamic DNS service will connect to the FortiGate unit.
IP Address	If you selected Static IP Address, enter the IP address of the remote peer.
Dynamic DNS	If you selected Dynamic DNS, enter the domain name of the remote peer.
Local Interface	This option is available in NAT mode only. Select the name of the interface through which remote peers or dialup clients connect to the FortiGate unit. By default, the local VPN gateway IP address is the IP address of the interface that you selected.
Mode	Main mode — the Phase 1 parameters are exchanged in multiple rounds with encrypted authentication information. Aggressive mode — the Phase 1 parameters are exchanged in single message with authentication information that is not encrypted. When the remote VPN peer has a dynamic IP address and is authenticated by a pre-shared key, you must select Aggressive mode if there is more than one dialup phase1 configuration for the interface IP address. When the remote VPN peer has a dynamic IP address and is authenticated by a certificate, you must select Aggressive mode if there is more than one Phase 1 configuration for the interface IP address and these Phase 1 configurations use different proposals.
Authentication Method	Select Preshared Key or RSA Signature.

 

Pre-shared Key	If you selected Pre-shared Key, enter the pre-shared key that the FortiGate unit will use to authenticate itself to the remote peer or dialup client during Phase 1 negotiations. You must define the same key at the remote peer or client. The key must contain at least 6 printable characters. For optimum protection against currently known attacks, the key must consist of a minimum of 16 randomly chosen alphanumeric characters. The limit is 128 characters.
Certificate Name	If you selected RSA Signature, select the name of the server certificate that the FortiGate unit will use to authenticate itself to the remote peer or dialup client during Phase 1 negotiations. For information about obtaining and loading the required server certificate, see the FortiOS User Authentication guide.
Peer Options	Peer options are available to authenticate VPN peers or clients, depending on the Remote Gateway and Authentication Method settings.
Any peer ID	Accept the local ID of any remote VPN peer or client. The FortiGate unit does not check identifiers (local IDs). You can set Mode to Aggressive or Main. You can use this option with RSA Signature authentication. But, for highest security, configure a PKI user/group for the peer and set Peer Options to Accept this peer certificate only.
This peer ID	This option is available when Aggressive Mode is enabled. Enter the identifier that is used to authenticate the remote peer. This identifier must match the Local ID that the remote peer’s administrator has configured. If the remote peer is a FortiGate unit, the identifier is specified in the Local ID field of the Advanced Phase 1 configuration. If the remote peer is a FortiClient user, the identifier is specified in the Local ID field, accessed by selecting Config in the Policy section of the VPN connection’s Advanced Settings. In circumstances where multiple remote dialup VPN tunnels exist, each tunnel must have a peer ID set.
Peer ID from dialup group	Authenticate multiple FortiGate or FortiClient dialup clients that use unique identifiers and unique pre-shared keys (or unique pre-shared keys only) through the same VPN tunnel. You must create a dialup user group for authentication purposes. Select the group from the list next to the Peer ID from dialup group option. You must set Mode to Aggressive when the dialup clients use unique identifiers and unique pre-shared keys. If the dialup clients use unique preshared keys only, you can set Mode to Main if there is only one dialup Phase 1 configuration for this interface IP address.

Phase 1 advanced configuration settings

You can use the following advanced parameters to select the encryption and authentication algorithms that the FortiGate unit uses to generate keys for the IKE exchange. You can also use the following advanced parameters to ensure the smooth operation of Phase 1 negotiations.

These settings are mainly configured in the CLI, although some options are available after the tunnel is created using the VPN Creation Wizard (using the Convert to Custom Tunnel option).

If the FortiGate unit will act as a VPN client, and you are using security certificates for authentication, set the Local ID to the distinguished name (DN) of the local server certificate that the FortiGate unit will use for authentication purposes.

Note that, since FortiOS 5.4, an exact match is required to optimize IKE’s gateway search utilizing binary trees. However, it is also possible to have partial matching of ‘user.peer:cn’ to match peers to gateways by performing a secondary match. When IKE receives IDi of type ASN1.DN, the first search is done with the whole DN string. If none is found, IKE will extract just the CN attribute value and perform a second search.

VXLAN over IPsec

Packets with VXLAN header are encapsulated within IPsec tunnel mode. To configure VXLAN over IPsec – CLI: config vpn ipsec phase1-interface/phase1 edit ipsec set interface <name> set encapsulation vxlan/gre set encapsulation-address ike/ipv4/ipv6 set encap-local-gw4 xxx.xxx.xxx.xxx set encap-remote-gw xxx.xxx.xxx.xxx next end

 

IPsec tunnel idle timer	You can define an idle timer for IPsec tunnels. When no traffic has passed through the tunnel for the configured idle-timeout value, the IPsec tunnel will be flushed. To configure IPsec tunnel idle timeout – CLI: config vpn ipsec phase1-interface edit p1 set idle-timeout [enable | disable] set idle-timeoutinterval <integer> //IPsec tunnel idle timeout in minutes (10 – 43200). end end
IPv6 Version	Select if you want to use IPv6 addresses for the remote gateway and interface IP addresses.
Local Gateway IP	Specify an IP address for the local end of the VPN tunnel. Select one of the following: Main Interface IP — The FortiGate unit obtains the IP address of the interface from the network interface settings. Specify — Enter a secondary address of the interface selected in the Phase 1 Local Interface field. You cannot configure Interface mode in a transparent mode VDOM.
Phase 1 Proposal	Select the encryption and authentication algorithms used to generate keys for protecting negotiations and add encryption and authentication algorithms as required. You need to select a minimum of one and a maximum of three combinations. The remote peer or client must be configured to use at least one of the proposals that you define. Select one of the following symmetric-key encryption algorithms: DES — Digital Encryption Standard, a 64-bit block algorithm that uses a 56-bit key. 3DES — Triple-DES; plain text is encrypted three times by three keys. AES128 — A 128-bit block algorithm that uses a 128-bit key. AES192 — A 128-bit block algorithm that uses a 192-bit key. AES256 — A 128-bit block algorithm that uses a 256-bit key. ChaCha20/Poly1305— A 128-bit block algorithm that uses a 128-bit key and a symmetric cipher. Only available for IKEv2.

 

	You can select either of the following message digests to check the authenticity of messages during an encrypted session: MD5 — Message Digest 5. SHA1 — Secure Hash Algorithm 1 – a 160-bit message digest. To specify one combination only, set the Encryption and Authentication options of the second combination to NULL. To specify a third combination, use the Add button beside the fields for the second combination.
Diffie-Hellman Group	Select one or more Diffie-Hellman groups from DH groups 1, 2, 5, and 14 through 21. At least one of the Diffie-Hellman Group settings on the remote peer or client must match one the selections on the FortiGate unit. Failure to match one or more DH groups will result in failed negotiations.
Keylife	Enter the time (in seconds) that must pass before the IKE encryption key expires. When the key expires, a new key is generated without interrupting service. The keylife can be from 120 to 172 800 seconds.
Local ID	If the FortiGate unit will act as a VPN client and you are using peer IDs for authentication purposes, enter the identifier that the FortiGate unit will supply to the VPN server during the Phase 1 exchange. If the FortiGate unit will act as a VPN client, and you are using security certificates for authentication, select the distinguished name (DN) of the local server certificate that the FortiGate unit will use for authentication purposes. If the FortiGate unit is a dialup client and will not be sharing a tunnel with other dialup clients (that is, the tunnel will be dedicated to this Fortinet dialup client), set Mode to Aggressive. Note that this Local ID value must match the peer ID value given for the remote VPN peer’s Peer Options.

 

XAuth	This option supports the authentication of dialup clients. It is available for IKE v1 only. Disable — Select if you do not use XAuth. Enable as Client — If the FortiGate unit is a dialup client, enter the user name and password that the FortiGate unit will need to authenticate itself to the remote XAuth server. Enable as Server — This is available only if Remote Gateway is set to Dialup User. Dialup clients authenticate as members of a dialup user group. You must first create a user group for the dialup clients that need access to the network behind the FortiGate unit. You must also configure the FortiGate unit to forward authentication requests to an external RADIUS or LDAP authentication server. Select a Server Type setting to determine the type of encryption method to use between the FortiGate unit, the XAuth client and the external authentication server, and then select the user group from the User Group list.
Username	Enter the user name that is used for authentication.
Password	Enter the password that is used for authentication.
NAT Traversal	Select the check box if a NAT device exists between the local FortiGate unit and the VPN peer or client. The local FortiGate unit and the VPN peer or client must have the same NAT traversal setting (both selected or both cleared) to connect reliably. Additionally, you can force IPsec to use NAT traversal. If NAT is set to Forced, the FortiGate will use a port value of zero when constructing the NAT discovery hash for the peer. This causes the peer to think it is behind a NAT device, and it will use UDP encapsulation for IPsec, even if no NAT is present. This approach maintains interoperability with any IPsec implementation that supports the NAT-T RFC.
Keepalive Frequency	If you enabled NAT-traversal, enter a keepalive frequency setting.
Dead Peer Detection	Select this check box to reestablish VPN tunnels on idle connections and clean up dead IKE peers if required. You can use this option to receive notification whenever a tunnel goes up or down, or to keep the tunnel connection open when no traffic is being generated inside the tunnel. For example, in scenarios where a dialup client or dynamic DNS peer connects from an IP address that changes periodically, traffic may be suspended while the IP address changes. With Dead Peer Detection selected, you can use the config vpn ipsec phase1 (tunnel mode) or config vpn ipsec phase1- interface (interface mode) CLI command to optionally specify a retry count and a retry interval.

IPsec VPN overview

This section provides a brief overview of IPsec technology and includes general information about how to configure IPsec VPNs using this guide.

The following topics are included in this section:

Types of VPNs

Planning your VPN

General preparation steps

How to use this guide to configure an IPsec VPN

VPN configurations interact with the firewall component of the FortiGate unit. There must be a security policy in place to permit traffic to pass between the private network and the VPN tunnel.

Security policies for VPNs specify:

• The FortiGate interface that provides the physical connection to the remote VPN gateway, usually an interface connected to the Internet
• The FortiGate interface that connects to the private network l IP addresses associated with data that has to be encrypted and decrypted l Optionally, a schedule that restricts when the VPN can operate l Optionally, the services (types of data) that can be sent

When the first packet of data that meets all of the conditions of the security policy arrives at the FortiGate unit, a VPN tunnel may be initiated and the encryption or decryption of data is performed automatically afterward. For more information, see Defining VPN security policies on page 1.

Where possible, you should create route-based VPNs. Generally, route-based VPNs are more flexible and easier to configure than policy-based VPNs — by default they are treated as interfaces. However, these two VPN types have different requirements that limit where they can be used.

Types of VPNs

FortiGate unit VPNs can be policy-based or route-based. There is little difference between the two types. In both cases, you specify Phase 1 and Phase 2 settings. However there is a difference in implementation. A route-based VPN creates a virtual IPsec network interface that applies encryption or decryption as needed to any traffic that it carries. That is why route-based VPNs are also known as interface-based VPNs. A policy-based VPN is implemented through a special security policy that applies the encryption you specified in the Phase 1 and Phase 2 settings.

Route-based VPNs

For a route-based VPN, you create two security policies between the virtual IPsec interface and the interface that connects to the private network. In one policy, the virtual interface is the source. In the other policy, the virtual interface is the destination. This creates bidirectional policies that ensure traffic will flow in both directions over the VPN.

A route-based VPN is also known as an interface-based VPN.

Each route-based IPsec VPN tunnel requires a virtual IPsec interface. As such, the amount of possible route-based IPsec VPNs is limited by the system.interface table size. The system.interface table size for most devices is 8192.

For a complete list of table sizes for all devices, refer to the Maximum Values table.

Policy-based VPNs

For a policy-based VPN, one security policy enables communication in both directions. You enable inbound and outbound traffic as needed within that policy, or create multiple policies of this type to handle different types of traffic differently. For example HTTPS traffic may not require the same level of scanning as FTP traffic.

A policy-based VPN is also known as a tunnel-mode VPN.

Comparing policy-based or route-based VPNs

For both VPN types you create Phase 1 and Phase 2 configurations. Both types are handled in the stateful inspection security layer, assuming there is no IPS or AV. For more information on the three security layers, see the FortiOS Troubleshooting guide.

The main difference is in the security policy.

You create a policy-based VPN by defining an IPSEC security policy between two network interfaces and associating it with the VPN tunnel (Phase 1) configuration.

You create a route-based VPN by creating a virtual IPsec interface. You then define a regular ACCEPT security policy to permit traffic to flow between the virtual IPsec interface and another network interface. And lastly, configure a static route to allow traffic over the VPN.

Where possible, you should create route-based VPNs. Generally, route-based VPNs are more flexible and easier to configure than policy-based VPNs — by default they are treated as interfaces. However, these two VPN types have different requirements that limit where they can be used.

Comparison of policy-based and route-based VPNs

Features	Policy-based	Route-based
Both NAT and transparent modes available	Yes	NAT mode only
L2TP-over-IPsec supported	Yes	Yes
GRE-over-IPsec supported	No	Yes
security policy requirements	Requires a security policy with IPSEC action that specifies the VPN tunnel	Requires only a simple security policy with ACCEPT action
Number of policies per VPN	One policy controls connections in both directions	A separate policy is required for connections in each direction

IPsec VPN concepts

Virtual Private Network (VPN) technology enables remote users to connect to private computer networks to gain access to their resources in a secure way. For example, an employee traveling or working from home can use a VPN to securely access the office network through the Internet.

Instead of remotely logging on to a private network using an unencrypted and unsecure Internet connection, the use of a VPN ensures that unauthorized parties cannot access the office network and cannot intercept any of the information that is exchanged between the employee and the office. It is also common to use a VPN to connect the private networks of two or more offices.

Fortinet offers VPN capabilities in the FortiGate Unified Threat Management (UTM) appliance and in the

FortiClient Endpoint Security suite of applications. A FortiGate unit can be installed on a private network, and FortiClient software can be installed on the user’s computer. It is also possible to use a FortiGate unit to connect to the private network instead of using FortiClient software.

This chapter discusses VPN terms and concepts including:

VPN tunnels

VPN gateways

Clients, servers, and peers

Encryption

Authentication

Phase 1 and Phase 2 settings

IKE and IPsec packet processing

VPN tunnels

The data path between a user’s computer and a private network through a VPN is referred to as a tunnel. Like a physical tunnel, the data path is accessible only at both ends. In the telecommuting scenario, the tunnel runs between the FortiClient application on the user’s PC, or a FortiGate unit or other network device and the FortiGate unit on the office private network.

Encapsulation makes this possible. IPsec packets pass from one end of the tunnel to the other and contain data packets that are exchanged between the local user and the remote private network. Encryption of the data packets ensures that any third-party who intercepts the IPsec packets can not access the data.

VPN tunnels

Encoded data going through a VPN tunnel

You can create a VPN tunnel between:

• A PC equipped with the FortiClient application and a FortiGate unit l Two FortiGate units
• Third-party VPN software and a FortiGate unit

For more information on third-party VPN software, refer to the Fortinet Knowledge Base for more information.

Tunnel templates

Several tunnel templates are available in the IPsec VPN Wizard that cover a variety of different types of IPsec VPN. A list of these templates appear on the first page of the Wizard, located at VPN > IPsec Wizard. The tunnel template list follows.

IPsec VPN Wizard options

VPN Type           Remote Device Type			NAT Options	Description
Site to Site	FortiGate		l No NAT between sites l This site is behind NAT l The remote site is behind NAT	Static tunnel between this FortiGate and a remote FortiGate.
	Cisco		l No NAT between sites l This site is behind NAT l The remote site is behind NAT	Static tunnel between this FortiGate and a remote Cisco firewall.

 

VPN Type	Remote Device Type		NAT Options	Description
Remote Access	Clientbased Native	FortiClient VPN for OS X, Windows, and Android	N/A	On-demand tunnel for users using the FortiClient software.
		Cisco AnyConnect	N/A	On-demand tunnel for users using the Cisco IPsec client.
		iOS Native	N/A	On-demand tunnel for iPhone/iPad users using the native iOS IPsec client.
		Android Native	N/A	On-demand tunnel for Android users using the native L2TP/IPsec client.
		Windows Native	N/A	On-demand tunnel for Android users using the native L2TP/IPsec client.
Custom	N/A		N/A	No Template.

In FortiOS 5.6.4+, the first step of the VPN Creation Wizard (VPN > IPsec Wizard) delineates the Remote Device Type (for Remote Access templates) between Client-based and Native in order to distinguish FortiClient and Cisco device options from native OS device options.

VPN tunnel list

Once you create an IPsec VPN tunnel, it appears in the VPN tunnel list at VPN > IPsec Tunnels. By default, the tunnel list indicates the name of the tunnel, its interface binding, the tunnel template used, and the tunnel status. If you right-click on the table header row, you can include columns for comments, IKE version, mode (aggressive vs main), phase 2 proposals, and reference number. The tunnel list page also includes the option to create a new tunnel, as well as the options to edit or delete a highlighted tunnel.

FortiView VPN tunnel map

A geospatial map can be found under FortiView > VPN Map to help visualize IPsec (and SSL) VPN connections to a FortiGate using Google Maps. This feature adds a geographical-IP API service for resolving spatial locations from IP addresses.

Introduction

The following is covered in this documentation section

IPsec VPN concepts explains the basic concepts that you need to understand about virtual private networks (VPNs).

IPsec VPN overview provides a brief overview of IPsec technology and includes general information about how to configure IPsec VPNs using this guide.

IPsec VPN in the web-based manager describes the IPsec VPN menu of the web-based manager interface.

Gateway-to-gateway configurations explains how to set up a basic gateway-to-gateway (site-to-site) IPsec VPN. In a gateway-to-gateway configuration, two FortiGate units create a VPN tunnel between two separate private networks.

Hub-and-spoke configurations describes how to set up hub-and-spoke IPsec VPNs. In a hub-and-spoke configuration, connections to a number of remote peers and/or clients radiate from a single, central FortiGate hub.

Dynamic DNS configuration describes how to configure a site-to-site VPN, in which one FortiGate unit has a static IP address and the other FortiGate unit has a dynamic IP address and a domain name.

FortiClient dialup-client configurations guides you through configuring a FortiClient dialup-client IPsec VPN. In a FortiClient dialup-client configuration, the FortiGate unit acts as a dialup server and VPN client functionality is provided by the FortiClient Endpoint Security application installed on a remote host.

FortiGate dialup-client configurations explains how to set up a FortiGate dialup-client IPsec VPN. In a FortiGate dialup-client configuration, a FortiGate unit with a static IP address acts as a dialup server and a FortiGate unit with a dynamic IP address initiates a VPN tunnel with the FortiGate dialup server.

Supporting IKE Mode config clients explains how to set up a FortiGate unit as either an IKE Mode Config server or client. IKE Mode Config is an alternative to DHCP over IPsec.

Internet-browsing configuration explains how to support secure web browsing performed by dialup VPN clients, and hosts behind a remote VPN peer. Remote users can access the private network behind the local FortiGate unit and browse the Internet securely. All traffic generated remotely is subject to the security policy that controls traffic on the private network behind the local FortiGate unit.

Redundant VPN configurations discusses the options for supporting redundant and partially redundant tunnels in an IPsec VPN configuration. A FortiGate unit can be configured to support redundant tunnels to the same remote peer if the FortiGate unit has more than one interface to the Internet.

Transparent mode VPNs describes two FortiGate units that create a VPN tunnel between two separate private networks transparently. In transparent mode, all FortiGate unit interfaces except the management interface are invisible at the network layer.

IPv6 IPsec VPNs describes FortiGate unit VPN capabilities for networks based on IPv6 addressing. This includes IPv4-over-IPv6 and IPv6-over-IPv4 tunnelling configurations. IPv6 IPsec VPNs are available in FortiOS 3.0 MR5 and later.

L2TP and IPsec (Microsoft VPN) explains how to support Microsoft Windows native VPN clients.

GRE over IPsec (Cisco VPN) explains how to interoperate with Cisco VPNs that use Generic Routing Encapsulation (GRE) protocol with IPsec.

Protecting OSPF with IPsec provides an example of protecting OSPF links with IPsec.

Redundant OSPF routing over IPsec provides an example of redundant secure communication between two remote networks using an OSPF VPN connection.

OSPF over dynamic IPsec provides an example of how to create a dynamic IPsec VPN tunnel that allows OSPF.

BGP over dynamic IPsec provides an example of how to create a dynamic IPsec VPN tunnel that allows BGP.

Phase 1 parameters provides detailed step-by-step procedures for configuring a FortiGate unit to accept a connection from a remote peer or dialup client. The basic Phase 1 parameters identify the remote peer or clients and support authentication through preshared keys or digital certificates. You can increase VPN connection security further using methods such as extended authentication (XAuth).

Phase 2 parameters provides detailed step-by-step procedures for configuring an IPsec VPN tunnel. During Phase 2, the specific IPsec security associations needed to implement security services are selected and a tunnel is established.

Defining VPN security policies explains how to specify the source and destination IP addresses of traffic transmitted through an IPsec VPN tunnel, and how to define a security encryption policy. Security policies control all IP traffic passing between a source address and a destination address.

Logging and monitoring and Troubleshooting provide VPN monitoring and troubleshooting procedures.