Log devices – FortiOS 6

Log devices

The FortiGate unit supports a variety of log devices, including the FortiCloud service and FortiAnalyzer units. This provides greater flexibility not only when choosing a log device, but also when your logging requirements need updating.

When you have developed a plan that meets your logging needs and requirements, you need to select the log device that is appropriate for that plan. A log device must be able to store all the logs you need, and if you require archiving those logs, you must consider what log devices support this option.

During this process of deciding what log device meets your needs and requirements, you must also figure out how to provide a backup solution in the event the log device that the FortiGate unit is sending logs to has become unavailable. A backup solution should be an important part of your log setup because it helps you to maintain all logs and prevents lost logs, or logs that are not sent to the log device. For example, a daily backup of log files to the FortiAnalyzer unit occurs at 5 pm.

Log devices provide a central location for storing logs recorded by the FortiGate unit. The following are log devices that the FortiGate unit supports:

l FortiGate system memory l Hard disk or AMC l SQL database (for FortiGate units that have a hard disk) l FortiAnalyzer unit l FortiCloud service l Syslog server

These log devices, except for the FortiGate system memory and local hard disk, can also be used as a backup solution. For example, you can configure logging to the FortiGate unit’s local disk, but also configure logging to a FortiCloud server and archive logs to both the FortiCloud server and a FortiAnalyzer unit.

FortiGate unit’s system memory and hard disk

The FortiGate unit’s system memory and hard disk can store all log types, including log archives and traffic logs. Traffic logs and log archives are larger files, and need a lot of room when being logged by the FortiGate unit.

When the system memory is full, the FortiGate unit overwrites the oldest messages, and all log messages stored in memory are cleared when the FortiGate unit restarts. By default, logging to memory is enabled. This means that most of the time you will only need to modify the default settings to your network logging requirements. Realtime logging occurs whenever memory logging is enabled, and is enabled by default. Real-time logging means that the activity is being recorded as it happens.

All FortiGate units 100D and larger are capable of disk logging, but it is disabled by default, as it is not recommended. For flash memory-based units, constant rewrites to flash drives can reduce the lifetime and efficiency of the memory. For hard-disk units, it can affect performance under heavy strain. Therefore, disk devices

logging must be manually enabled in the CLI under config log disk setting to appear in the interface at all.

Models without a hard disk are not recommended for disk logging. For all units, disk logging must be enabled in the CLI. For some low-end and older models, disk logging is unavailable. Check a product’s Feature Matrix for more information. In either case, Fortinet recommends using either a FortiAnalyzer unit or the FortiCloud service.

Local disk or memory logging is not required for you to configure logging to a FortiAnalyzer unit.

If you are registered with the FortiCloud service, your unit will log both locally and to the service by default. In order to configure the rate and time of uploads to the service, you must register a contract account for the FortiCloud service, which will also grant you additional space.

FortiAnalyzer unit

The FortiAnalyzer unit can log all FortiGate features, which includes log archives. You can also configure the FortiGate unit to upload logs to the FortiAnalyzer unit at a scheduled time.

Encryption of the logs is supported by default and logs are sent using SSL VPN. When the FortiAnalyzer and FortiGate units have SSL encryption, both must choose a setting for the enc-algorithm command (CLI) for encryption to take place. By default, this is enabled and the default setting is a SSL communication with high and medium encryption algorithms. The setting that you choose must be the same for both.

FortiGate units can support logging to multiple FortiAnalyzer units. This logging solution is a backup redundancy solution, since logs are sent to all three units and whenever one of the FortiAnalyzer units fails, the others still carry on storing logs.

If you are using evaluation software FortiGate and FortiAnalyzer-VM images, you will only be able to use lowlevel encryption.

The FortiGate unit can also connect to a FortiAnalyzer unit using Automatic Discovery. Automatic Discovery is a method of establishing a connection to a FortiAnalyzer unit by using the FortiGate unit to find a FortiAnalyzer unit on the network. The Fortinet Discovery Protocol (FDP) is used to located the FortiAnalyzer unit. Both the FortiGate and FortiAnalyzer units must be on the same subnet to use FDP, and they must also be able to connect using UDP.

When you enable automatic discovery in the CLI, the FortiGate unit uses HELLO packets to locate any

FortiAnalyzer units that are available on the network within the same subnet. When the FortiGate unit discovers a FortiAnalyzer unit, the FortiGate unit automatically enables logging to the FortiAnalyzer unit and begins sending log data.

Syslog server

A Syslog server is a remote computer running syslog software. Syslog is a standard for forwarding log messages in an IP network, and can be used when considering a log backup solution for your network logging requirements. Logs that are generated in real-time are sent to the syslog server in real time with no queueing, so it can be an ideal solution for comprehensive logging, or collecting logs for later systematic analysis.

FortiGate units support the reliable syslog feature, which is based on RFC 3195. Reliable syslog logging uses TCP, which ensures that connections are set up, including that packets are transmitted.

There are several profiles available for reliable syslog, but only the RAW profile is currently supported on the FortiGate units. The RAW profile is designed to provide a high-performance, low-impact footprint using essentially the same format as the existing UDP-based syslog service. The reliable syslog feature is available on FortiGate units running FortiOS 4.0 MR1 and higher.

When enabling the reliable syslog (available only in the CLI), TCP is used. The feature is disabled by default, and when enabled, the FortiGate unit automatically changes the port number to TCP 601. This is based on RFC 3195. The default port for syslog is port 514.

If you are using the local hard disk on a device for WAN Optimization, it will not prevent you from logging to remote FortiAnalyzer devices or Syslog servers. Some models have two hard disks, allowing both local logging and Wan Opt.

If you have Virtual Domains configured, each VDOM may only be assigned one FortiAnalyzer device and one Syslog server, by overriding the global configuration. The root VDOM is not limited in this way.

How to choose a log device for your network topology

When planning the log requirements, you must also consider your network’s topology and whether archiving is required, such as if there is a legal requirement to keep a historical record of network activity. The following explains what steps to take when choosing a log device for your specific network topology.

  1. What is the scope of your network topology?

If it is a SOHO/SMB network, then logging to the FortiGate unit’s local hard disk or the default FortiCloud service would be efficient. If the network topology is a large enterprise, you will need FortiAnalyzer units, a FortiCloud contract, Syslog servers, or any combination.

  1. Is archiving required?

If the network activity that is being logged needs to be archived, then, depending on your network topology, you would choose a FortiAnalyzer unit. FortiAnalyzer units store archives in the same way that FortiGate units do, but are able to store large amounts of logs and archives.

  1. When troubleshooting, you may want to log a larger amount of traffic; how much storage space will you need?

Logs can be configured to roll, which is similar to zipping a file; this will lower the space requirements needed to contain them. You can also download logs from the FortiGate unit and save them on a server or on a computer to view and access later, to prevent them from piling up and being overwritten. If you’re regularly logging large amounts of traffic, you should consider a FortiAnalyzer or FortiCloud account .

  1. Should I invest in a log device that can grow as my network grows?

All networks grow, so investing in a device that can grow with your network and that can be expanded is a good investment. For example, if you currently have a SOHO/SMB topology, but see growth already starting, a FortiAnalyzer unit would be best. A FortiAnalyzer unit provides ample storage space, and you can add two more FortiAnalyzer units to access additional storage and create a redundancy log backup solution.

How to create a backup solution for logging

The following helps to explain how to create a log backup solution for a small network topology. This example has one FortiAnalyzer unit and a subscription to the FortiCloud Service.

Example of an integrated FortiAnalyzer unit and Syslog servers in a network

  1. Log in to the CLI and modify what features will be logged to the FortiAnalyzer unit as well as the settings to the default log device, the FortiGate unit’s hard drive.

By default, the FortiGate unit logs to either the system memory or hard drive, whichever is available on the FortiGate unit. Low-end FortiGate units may have logging disabled by default.

  1. In the CLI, use the config log fortianalyzer setting command to configure logging to the

FortiAnalyzer unit.

You can only configure log settings for the FortiAnalyzer unit in the CLI. Configuring to upload logs to a FortiAnalyzer unit can be configured in both the CLI and web-based manager.

  1. In the CLI, configure the settings for the Syslog server; also enable reliable syslog as well.

Reliable syslog verifies that logs are sent to the syslog server. When you enable this setting, the default port becomes port 601.


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