Explicit proxy

• For explicit proxies, when configuring limits on the number of concurrent users, you need to allow for the number of users based on their authentication method. Otherwise you may run out of user resources prematurely.
• Each session-based authenticated user is counted as a single user using their authentication membership (RADIUS, LDAP, FSSO, local database etc.) to match users in other sessions. So one authenticated user in multiple sessions is still one user.
• For all other situations, the source IP address is used to determine a user. All sessions from a single source address are assumed to be from the same user.
• Set the explicit web proxy and explicit FTP proxy Default Firewall Policy Action to Deny. This means that a firewall policy is required to use these explicit proxies, allowing you to control access and impose security features.

Do not enable the explicit web or FTP proxy on an interface connected to the Internet. This is a security risk because anyone on the Internet who finds the proxy could use it to hide their source address. If you must enable the proxy on such an interface make sure authentication is required to use the proxy.

Virtual Domains (VDOMs)

VDOMs can provide separate firewall policies and, in NAT mode, completely separate configurations for routing and VPN services for each connected network or organization. This section provides a list of best practices for configuring VDOMs.

Per-VDOM resource settings

While Global resources apply to resources shared by the whole FortiGate unit, per-VDOM resources are specific to only one Virtual Domain.

By default all the per-VDOM resource settings are set to no limits. This means that any single VDOM can use up all the resources of the entire FortiGate unit if it needs to do so. This would starve the other VDOMs for resources to the point where they would be unable to function. For this reason, it is recommended that you set some maximums on resources that are most vital to your customers.

Virtual domains in NAT mode

Once you have enabled virtual domains and created one or more VDOMs, you need to configure them. It is recommended that you perform the following tasks in the order given (while you may not require all for your network topology):

1. Change the management virtual domain.
2. Configure FortiGate interfaces for your VDOMs in NAT mode.
3. Configure VDOM routing.
4. Configure security policies for VDOMs in NAT mode.
5. Configure UTM profiles for VDOMs in NAT mode.
6. Test the configuration.

Virtual clustering

If you decide to disable override for clurstering, as a result of persistent renegotiating, you should disable it for both cluster units.

WAN Optimization

WAN Optimization features require significant memory resources and generate a high amount of I/O on disk. Before enabling WAN Optimization, ensure that the memory usage is not too high. If possible, avoid other disk-intensive features such as heavy traffic logging on the same disk as the one configured for WAN Optimization needs.

In general, it is preferable to enable the Transparent Mode checkbox and ensure that routing between the two endpoints is acceptable. Some protocols may not work well without enabling Transparent Mode.

Other best practices for utilizing the WAN Optimization feature follow.

Sharing the WAN Opt. tunnel for traffic of the same nature

WAN optimization tunnel sharing is recommended for similar types of WAN optimization traffic (such as CIFS traffic from different servers). However, tunnel sharing for different types of traffic is not recommended. For example, aggressive and non-aggressive protocols should not share the same tunnel.

Ordering WAN Opt. rules appropriately

l Precise, port specific WAN Optimization rules should be at the top of the list. l Generic rules, such as overall TCP, should be at the bottom of the list.

Avoiding mixing protocols in a WAN Opt. tunnel

Different protocols may be more or less talkative or interactive . Mixing protocols in a tunnel may result in a delay for some of them. It is recommended to define protocol specific wan-optimization rules and restrict the ports to the necessary ones only for performance reasons.

Setting correct configuration options for CIFS WAN Opt.

Ensure that the WAN Optimization rules cover TCP ports 139 and 445 (on the same or two different rules). Also ensure that Transparent Mode is selected.

Setting correct configuration options for MAPI WAN Opt.

For MAPI WAN Optimization, only specify a rule with TCP port 135 (unless the MAPI control port is configured differently). Derived data sessions using other random ports will be handled by the CIFS wan-optimization daemon even with only the control port configured.

WAN Optimization

Testing WAN Opt. in a lab

• Ensure that WAN emulators are used to simulate the WAN. If no WAN emulator is used, it is expected to have better results without WAN Optimization than with WAN Optimization.
• To test the difference between cold transfers (first-time transfers) and warm transfers, it is recommended to generate a random file of the cold transfer to ensure that the test is the first time that the file has been seen.

Regarding byte compression and type of file

Enabling byte compression on file transfers already compressed (.jpeg files, compressed archive, etc.) won’t provide any performance increase and could be seen as a misuse of CPU resources.

Regarding network address translation (NAT)

Selecting the NAT feature in a security policy does not have any influence on WAN Optimization traffic.

High Availability

There is no benefit to using active-active mode, so for pure WAN Optimization needs, use active-passive mode. Refer to the FGCP high availability section for other best practices related to HA.

Authentication with specific peers

Configure WAN optimization authentication with specific peers. Accepting any peer is not recommended as this can be less secure.

FGCP high availability

Fortinet suggests the following practices related to high availability:

• Use Active-Active HA to distribute TCP and UTM sessions among multiple cluster units. An active-active cluster may have higher throughput than a standalone FortiGate unit or than an active-passive cluster.
• Use a different host name on each FortiGate unit when configuring an HA cluster. Fewer steps are required to add host names to each cluster unit before configuring HA and forming a cluster.
• Consider adding an Alias to the interfaces used for the HA heartbeat so that you always get a reminder about what these interfaces are being used for.
• Enabling load-balance-all can increase device and network load since more traffic is load-balanced. This may be appropriate for use in a deployment using the firewall capabilities of the FortiGate unit and IPS but no other content inspection.
• An advantage of using session pickup is that non-content inspection sessions will be picked up by the new primary unit after a failover. The disadvantage is that the cluster generates more heartbeat traffic to support session pickup as a larger portion of the session table must be synchronized. Session pickup should be configured only when required and is not recommended for use with SOHO FortiGate models. Session pickup should only be used if the primary heartbeat link is dedicated (otherwise the additional HA heartbeat traffic could affect network performance).
• If session pickup is not selected, after a device or link failover all sessions are briefly interrupted and must be reestablished at the application level after the cluster renegotiates. For example, after a failover, users browsing the web can just refresh their browsers to resume browsing. Users downloading large files may have to restart their download after a failover. Other protocols may experience data loss and some protocols may require sessions to be manually restarted. For example, a user downloading files with FTP may have to either restart downloads or restart their FTP client.
• If you need to enable session pickup, consider enabling session-pickup-delay to improve performance by reducing the number of sessions that are synchronized.
• Consider using the session-sync-dev option to move session synchronization traffic off the HA heartbeat link to one or more dedicated session synchronization interfaces.
• To avoid unpredictable results, when you connect a switch to multiple redundant or aggregate interfaces in an active-passive cluster you should configure separate redundant or aggregate interfaces on the switch; one for each cluster unit.
• Use SNMP, syslog, or email alerts to monitor a cluster for failover messages. Alert messages about cluster failovers may help find and diagnose network problems quickly and efficiently.

Heartbeat interfaces

Fortinet suggests the following practices related to heartbeat interfaces:

FGCP high availability

• Configure at least two heartbeat interfaces and set these interfaces to have different priorities.
• For clusters of two FortiGate units, as much as possible, heartbeat interfaces should be directly connected using patch cables (without involving other network equipment such as switches). If switches have to be used they should not be used for other network traffic that could flood the switches and cause heartbeat delays.
• If you cannot use a dedicated switch, the use of a dedicated VLAN can help limit the broadcast domain to protect the heartbeat traffic and the bandwidth it creates.
• For clusters of three or four FortiGate units, use switches to connect heartbeat interfaces. The corresponding heartbeat interface of each FortiGate unit in the cluster must be connected to the same switch. For improved redundancy use a different switch for each heartbeat interface. In that way if the switch connecting one of the heartbeat interfaces fails or is unplugged, heartbeat traffic can continue on the other heartbeat interfaces and switch.
• Isolate heartbeat interfaces from user networks. Heartbeat packets contain sensitive cluster configuration information and can consume a considerable amount of network bandwidth. If the cluster consists of two FortiGate units, connect the heartbeat interfaces directly using a crossover cable or a regular Ethernet cable. For clusters with more than two units, connect heartbeat interfaces to a separate switch that is not connected to any network.
• If heartbeat traffic cannot be isolated from user networks, enable heartbeat message encryption and authentication to protect cluster information.
• Configure and connect redundant heartbeat interfaces so that if one heartbeat interface fails or becomes disconnected, HA heartbeat traffic can continue to be transmitted using the backup heartbeat interface. If heartbeat communication fails, all cluster members will think they are the primary unit resulting in multiple devices on the network with the same IP addresses and MAC addresses (condition referred to as Split Brain) and communication will be disrupted until heartbeat communication can be reestablished.
• Do not monitor dedicated heartbeat interfaces; monitor those interfaces whose failure should trigger a device failover.
• Where possible at least one heartbeat interface should not be connected to an NP4 or NP6 processor to avoid NP4 or NP6-related problems from affecting heartbeat traffic.
• Where possible, the heartbeat interfaces should not be connected to an NP4 or NP6 processor that is also processing network traffic.
• Where possible, each heartbeat interface should be connected to a different NP4 or NP6 processor.
• Any FortiGate interface can be used as a heartbeat interface including 10/100/1000Base-T, SFP, QSFP fiber and copper, and so on. If you set up two or more interfaces as heartbeat interfaces each interface can be a different type and speed.

Interface monitoring (port monitoring)

Fortinet suggests the following practices related to interface monitoring (also called port monitoring):

• Wait until a cluster is up and running and all interfaces are connected before enabling interface monitoring. A monitored interface can easily become disconnected during initial setup and cause failovers to occur before the cluster is fully configured and tested.
• Monitor interfaces connected to networks that process high priority traffic so that the cluster maintains connections to these networks if a failure occurs.
• Avoid configuring interface monitoring for all interfaces.
• Supplement interface monitoring with remote link failover. Configure remote link failover to maintain packet flow if a link not directly connected to a cluster unit (for example, between a switch connected to a cluster interface and the network) fails.

Networking

When configuring your network, ensure that there is no ‘back door’ access to the protected network. For example, if there is a wireless access point, it must be appropriately protected with password and encryption.

Be sure to also maintain an up-to-date network diagram which includes IP addressing, cabling, and network elements.

Routing configuration

• Always configure a default route.
• Add blackhole routes for subnets reachable using VPN tunnels. This ensures that if a VPN tunnel goes down, traffic is not mistakingly routed to the Internet unencrypted.

Policy routing

Keep the number of policy routes to a minimum to optimize performance in route lookup and to simplify troubleshooting.

Dynamic routing

• Select a Router ID that matches an IP assigned to an interface. This avoids the likelihood of having two devices with the same router ID.
• For routing over an IPsec tunnel, assign IP addresses to both ends of the tunnel.

Advanced routing

Use the following best practices for advanced routing when dealing with Border Gateway Protocol (BGP) and Open Shortest Path First (OSPF).

Border Gateway Protocol (BGP)

If you are using BGP, it is recommended that you enable soft-reconfiguration. This has two benefits:

• It allows you to perform ‘soft clear’ of peers after a change is made to a BGP policy.
• It provides greater visibility into the specific prefixes learned from each neighbor.

Leave soft-reconfiguration disabled if your FortiGate does not have much unused memory. Soft-reconfiguration requires keeping separate copies of prefixes received and advertised, in addition to the local BGP database.

Networking

Open Shortest Path First (OSPF)

l Avoid use of passive interfaces wherever possible. l Avoid use of virtual links to connect areas. All areas should be designed to connect directly to the backbone area. l Ensure that all backbone routers have a minimum of two peering connections to other backbone neighbors. l An entire OSPF domain should be under common administration.

Network Address Translation (NAT)

• Beware of misconfiguring the IP Pool range. Double-check the start and end IP addresses of each IP pool. The IP pool should not overlap with addresses assigned to FortiGate interfaces or to any hosts on directly connected networks.
• If you have internal and external users accessing the same servers, use split DNS to offer an internal IP to internal users so that they don’t have to use the external-facing VIP.

Configuring NAT

Do not enable NAT for inbound traffic unless it is required by an application. If, for example, NAT is enabled for inbound SMTP traffic, the SMTP server might act as an open relay.

Transparent Mode

• Do not connect two ports to the same VLAN on a switch or to the same hub. Some Layer 2 switches become unstable when they detect the same MAC address originating on more than one switch interface or from more than one VLAN.
• If you operate multiple VLANs on your FortiGate unit, assign each VLAN id to its own forwarding domain to ensure that the scope of the broadcast does not extend beyond the VLAN it originated in.

To protect against Layer 2 loops:

• Enable stpforward on all interfaces. l Use separate VDOMs for production traffic (TP mode VDOM) and management traffic (NAT mode VDOM).
• Only place those interfaces used for production in the TP mode VDOM. Place all other interfaces in the NAT mode VDOM. This protects against potential Layer 2 loops.

Using virtual IPs (VIPs)

• Use the external IP of 0.0.0.0 when creating a VIP for a FortiGate unit where the external interface IP address is dynamically assigned.
• Be sure to select the correct external interface when creating a new virtual IP (VIP). The external interface should be set to the interface at which the FortiGate unit receives connection requests from external networks.

Policy configuration

Configuring the FortiGate unit with an ‘allow all’ traffic policy is very undesirable. While this does greatly simplify the configuration, it is less secure. As a security measure, it is best practice for the policy rulebase to ‘deny’ by default, and not the other way around.

Policy configuration changes

On a heavy-loaded system, plan configuration changes during low usage periods in order to minimize impact on CPU usage and established sessions. In this scenario, it is considered a best practice to de-accelerate the hardwareaccelerated sessions.

You can configure de-accelerated behaviour on hardware-accelerated sessions using CLI commands to control how the processor manages policy configuration changes. The following CLI commands are to be used:

config system settings set firewall-session-dirty { check-all | check-new | check-policy-option }

end where you want the following to be true:

Policy whitelisting

• Allow only the necessary inbound and outbound traffic.
• If possible, limit traffic to specific addresses or subnets. This allows the FortiGate unit to drop traffic to and from unexpected addresses.

IPS and DoS policies

• Because it is critical to guard against attacks on services that you make available to the public, configure IPS signatures to block matching signatures. For example, if you have a web server, configure the action of web server signatures to Block.
• Your FortiGate unit includes IPS signatures written to protect specific software titles from DoS attacks. Enable the signatures for the software you have installed and set the signature action to Block.
• DoS attacks are launched against vulnerabilities. Maintain a FortiGuard IPS subscription to ensure your FortiGate unit automatically receives new and updated IPS signatures as they are released.

Policy configuration

• Use and configure DoS policies to appropriate levels based on your network traffic and topology. This will help drop traffic if an abnormal amount is received. The key is to set a good threshold. The threshold defines the maximum number of sessions/packets per second of normal traffic. If the threshold is exceeded, the action is triggered. Threshold defaults are general recommendations, but your network may require very different values. One way to find the correct values for your environment is to set the action to Pass and enable logging. Observe the logs and adjust the threshold values until you can determine the value at which normal traffic begins to generate attack reports. Set the threshold above this value with the margin you want. Note that the smaller the margin, the more protected your system will be from DoS attacks, but your system will also be more likely to generate false alarms.

Patch management

When vulnerabilities are discovered in software, the software vendors release updates that fix these problems. Keeping your software and operating system up-to-date is a vital step to prevent infection and defend against attacks.

• Follow the latest advisories and reports on the FortiGuard webpage. l Apply updates to all software as the updates become available.
• FortiGuard Vulnerability Management can help identify security weaknesses in your network. This subscription service is available through FortiScan and FortiAnalyzer units.
• Apply firmware updates to your FortiGate unit as they are released.
• Subscribe to FortiGuard AntiVirus and IPS services, so that AntiVirus and IPS scanning engines are automatically updated when new version are released.

Web filtering

FortiGuard Web Filtering can help stop infections from malware sites and help prevent communication if an infection occurs.

• Enable FortiGuard Web Filtering at the network edge. l Install the FortiClient application and use FortiGuard Web Filtering on any systems that bypass your FortiGate unit.
• Block categories such as Pornography, Malware, Spyware, and Phishing. These categories are more likely to be dangerous