FortiOS 6 – Supporting IKE Mode Config clients

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Supporting IKE Mode Config clients

IKE Mode Config is an alternative to DHCP over IPsec. A FortiGate unit can be configured as either an IKE Mode Config server or client. This chapter contains the following sections:

IKE Mode Config overview

Automatic configuration overview

IKE Mode Config method

IKE Mode Config overview

Dialup VPN clients connect to a FortiGate unit that acts as a VPN server, providing the client the necessary configuration information to establish a VPN tunnel. The configuration information typically includes a virtual IP address, netmask, and DNS server address.

IKE Mode Config is available only for VPNs that are route-based, also known as interface-based. A FortiGate unit can function as either an IKE Configuration Method server or client. IKE Mode Config is configurable only in the CLI.

Automatic configuration overview

VPN configuration for remote clients is simpler if it is automated. Several protocols support automatic configuration:

  • The Fortinet FortiClient Endpoint Security application can completely configure a VPN connection with a suitably configured FortiGate unit given only the FortiGate unit’s address. This protocol is exclusive to Fortinet. For more information, see FortiClient dialup-client configurations on page 1.
  • DHCP over IPsec can assign an IP address, Domain, DNS and WINS addresses. The user must first configure IPsec parameters such as gateway address, encryption and authentication algorithms.
  • IKE Mode Config can configure host IP address, Domain, DNS and WINS addresses. The user must first configure IPsec parameters such as gateway address, encryption and authentication algorithms. Several network equipment vendors support IKE Mode Config, which is described in the ISAKMP Configuration Method document draft-dukesike-mode-cfg-02.txt.

This chapter describes how to configure a FortiGate unit as either an IKE Mode Config server or client.

IKE Mode Config method

IKE Mode Config is configured with the CLI command config vpn ipsec phase1-interface. The mode-cfg variable enables IKE Mode Config. The type field determines whether you are creating an IKE Mode Config server or a client. Setting type to dynamic creates a server configuration, otherwise the configuration is a client.

Creating an IKE Mode Config client

If the FortiGate unit will connect as a dialup client to a remote gateway that supports IKE Mode Config, the relevant vpn ipsec phase1-interface variables are as follows:

Variable Description
ike-version 1 IKE v1 is the default for FortiGate IPsec VPNs.

IKE Mode Config is also compatible with IKE v2 (RFC 4306). Use syntax ike-version 2.
mode-cfg enable Enable IKE Mode Config.
type {ddns | static} If you set type to dynamic, an IKE Mode Config server is created.
assign-ip {enable | disable} Enable to request an IP address from the server.
interface <interface_ name> This is a regular IPsec VPN field. Specify the physical, aggregate, or VLAN interface to which the IPsec tunnel will be bound.
proposal <encryption_ combination> This is a regular IPsec VPN field that determines the encryption and authentication settings that the client will accept. For more information, see Phase 1 parameters on page 46.
ip-version <4 | 6> This is a regular IPsec VPN field. By default, IPsec VPNs use IPv4 addressing. You can set ip-version to 6 to create a VPN with IPv6 addressing.
ipv4-split-exclude ipv6-split-exclude This command allows the administrator to specify that default traffic flows over the IPsec tunnel except for specified subnets. This is the opposite of the supported split-include feature which allows the administrator to specify that default traffic should not flow over the IPsec tunnel except for specified subnets.

For a complete list of available variables, see the CLI Reference.

IKE Mode Config client example – CLI

In this example, the FortiGate unit connects to a VPN gateway with a static IP address that can be reached through Port 1. Only the port, gateway and proposal information needs to be configured. All other configuration information will come from the IKE Mode Config server.

config vpn ipsec phase1-interface edit vpn1 set ip-version 4 set type static set remote-gw <gw_address> set interface port 1 set proposal 3des-sha1 aes128-sha1 set mode-cfg enable

set assign-ip enable

end

Creating an IKE Mode Config server

If the FortiGate unit will accept connection requests from dialup clients that support IKE Mode Config, the following vpn ipsec phase1-interface settings are required before any other configuration is attempted:

Variable Description
ike-version 1 IKE v1 is the default for FortiGate IPsec VPNs.

IKE Mode Config is also compatible with IKE v2 (RFC 4306). Use syntax ike-version 2.
mode-cfg enable Enable IKE Mode Config.
type dynamic Any other setting creates an IKE Mode Config client.
interface <interface_ name> This is a regular IPsec VPN field. Specify the physical, aggregate, or VLAN interface to which the IPsec tunnel will be bound.
proposal <encryption_ combination> This is a regular IPsec VPN field that determines the encryption and authentication settings that the server will accept. For more information, see Phase 1 parameters on page 46.
ip-version <4 | 6> This is a regular IPsec VPN field. By default, IPsec VPNs use IPv4 addressing. You can set ip-version to 6 to create a VPN with IPv6 addressing.

IKE Mode Config server example – CLI

In this example, the FortiGate unit assigns IKE Mode Config clients addresses in the range of 10.11.101.160 through 10.11.101.180. DNS and WINS server addresses are also provided. The public interface of the FortiGate unit is Port 1.

When IKE Mode-Configuration is enabled, multiple server IPs can be defined in IPsec Phase 1.

The ipv4-split-include variable specifies a firewall address that represents the networks to which the clients will have access. This destination IP address information is sent to the clients.

Only the CLI fields required for IKE Mode Config are shown here. For detailed information about these variables, see the FortiGate CLI Reference.

config vpn ipsec phase1-interface edit “vpn-p1” set type dynamic set interface “wan1” set xauthtype auto set mode aggressive set mode-cfg enable

set proposal 3des-sha1 aes128-sha1 set dpd disable set dhgrp 2

set xauthexpire on-rekey set authusrgrp “FG-Group1” set ipv4-start-ip 10.10.10.10 set ipv4-end-ip 10.10.10.20 set ipv4-dns-server1 1.1.1.1 set ipv4-dns-server2 2.2.2.2 set ipv4-dns-server3 3.3.3.3 set ipv4-wins-server1 4.4.4.4 set ipv4-wins-server2 5.5.5.5 set domain “fgt1c-domain” set banner “fgt111C-banner”

set backup-gateway “100.100.100.1” “host1.com” “host2” set ipv4-split-include OfficeLAN

end

IP address assignment

After you have enabled the basic configuration, you can configure IP address assignment for clients, as well as DNS and WINS server assignment. Usually you will want to assign IP addresses to clients.

The simplest method to assign IP addresses to clients is to assign addresses from a specific range, similar to a DHCP server.

If your clients are authenticated by a RADIUS server, you can obtain the user’s IP address assignment from the Framed-IP-Address attribute. The user must be authenticated using XAuth.

IKE Mode Config can also use a remote DHCP server to assign the client IP addresses. Up to eight addresses can be selected for either IPv4 or IPv6. After the DHCP proxy has been configured, the assign-ip-from command is used to assign IP addresses via DHCP.

Assigning IP addresses from an address range – CLI

If your VPN uses IPv4 addresses,

config vpn ipsec phase1-interface edit vpn1 set mode-cfg-ipversion 4 set assign-ip enable set assign-ip-type ip set assign-ip-from range set ipv4-start-ip <range_start> set ipv4-end-ip <range_end> set ipv4-netmask <netmask>

end

If your VPN uses IPv6 addresses,

config vpn ipsec phase1-interface edit vpn1 set mode-cfg-ipversion 6 set assign-ip enable set assign-ip-type ip set assign-ip-from range set ipv6-start-ip <range_start> set ipv6-end-ip <range_end> end

Assigning IP addresses from a RADIUS server – CLI

The users must be authenticated by a RADIUS server and assigned to the FortiGate user group <grpname>.

Since the IP address will not be static, type is set to dynamic, and mode-cfg is enabled. This is IKE

Configuration Method so that compatible clients can configure themselves with settings that the FortiGate unit provides.

config vpn ipsec phase1-interface edit vpn1 set type dynamic set mode-cfg enable set assign-ip enable set assign-ip-from usrgrp set xauthtype auto set authusrgrp <grpname>

end

Assigning IP address from DHCP – CLI

The DHCP proxy must first be enabled for IKE Mode Config to use DHCP to assign the VPN client IP address(es).

config system settings set dhcp-proxy enable set dhcp-server-ip [ipv4 address] set dhcp6-server-ip [ipv6-address]

(Up to eight server addresses can be configured) end

config vpn ipsec phase1-interface edit vpn1 set mode-cfg enable set assign-ip-from dhcp

next

end

Assigning IP address from a named firewall address/group – CLI

config vpn ipsec phase1-interface edit <name>vpn1 set type dynamic set assign-ip-from name set ipv4-name <name> set ipv6-name <name>

next

end

Certificate groups

IKE certificate groups consisting of up to four RSA certificates can be used in IKE Phase 1. Since CA and local certificates are global, the IKE daemon loads them once for all VDOMs and indexes them into trees based on subject and public key hash (for CA certificates), or certificate name (for local certicates). Certifcates are linked together based on the issuer, and certificate chains are built by traversing these links. This reduces the need to keep multiple copies of certificates that could exist in multiple chains.

IKE certificate groups can be configured through the CLI.

Configuring the IKE local ID – CLI

config vpn certificate local edit <name> set ike-localid <string> set ike-localid-type {asnldn | fqdn}

end

Split-exclude in IKEv1 mode-cfg

This feature allows the administrator to specify when using IKEv1 Configuration Method that default traffic flows over the IPsec tunnel except for specified subnets. This is the opposite of the supported split-include feature which allows the administrator to specify that default traffic should not flow over the IPsec tunnel except for specified subnets.

The split-include and split-exclude options can both be specified at the same time. Whether a client does the right thing when both are specified depends on the client.

Syntax

config vpn ipsec {phase1 | phase1-interface} edit <name> set ike-version 1 set type dynamic set mode-cfg enable set ipv4-split-exclude {all | none | address} set ipv6-split-exclude {all | none | address}

next end

 

This entry was posted in Administration Guides, FortiGate, FortiOS 6 on by .

About Mike

Michael Pruett, CISSP has a wide range of cyber-security and network engineering expertise. The plethora of vendors that resell hardware but have zero engineering knowledge resulting in the wrong hardware or configuration being deployed is a major pet peeve of Michael's. This site was started in an effort to spread information while providing the option of quality consulting services at a much lower price than Fortinet Professional Services. Owns PacketLlama.Com (Fortinet Hardware Sales) and Office Of The CISO, LLC (Cybersecurity consulting firm).

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