Fortinet Document Library

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Table of Contents

Handbook

Configuring an IPv4 connection limit policy

The firewall connection limit policy allows or denies traffic based on a matching tuple: source address, destination address, and service; and connection count. The purpose is to detect anomalous connection requests.

The limit you specify can be based on the following counts:

  • Count of concurrent sessions that match the tuple.
  • Count of concurrent sessions from a single host that match the tuple.

The FortiADC system evaluates firewall connection limit policy rules before other rules. It matches traffic against the connection limit table, beginning with the first rule. If no rule matches, the connection is forwarded for further processing. If a rule matches, and the limit has not been reached, the connection is forwarded for further processing. If a rule matches and the limit has been reached, the connection is dropped.

By default, if firewall connection limit rules are not configured, the system does not perform connection limit policy processing. The firewall connection limit can be configured for non-SLB traffic and for Layer 7 SLB traffic, but not Layer 4 SLB traffic.

Note: The purpose of the firewall connection limit is distinct from the virtual server connection limit. The firewall connection limit setting is a security setting; the virtual server connection limit is a capacity setting.

Before you begin:

  • You must have a good understanding and knowledge of the capacity of your backend servers.
  • You must have created the address configuration objects and service configuration objects that define the matching tuple in your connection limit rules.
  • You must have Read-Write permission for Firewall settings.
To configure a firewall connection limit:
  1. Click Network Security > Firewall > IPv4 Connection Limit Policy.
  2. Click Create New to display the configuration editor.
  3. Complete the configuration as described in Connection limit configuration.
  4. Save the configuration.
  5. Reorder rules, as necessary.

Connection limit configuration

Settings Guidelines

Name

Configuration name. Valid characters are A-Z, a-z, 0-9, _, and -. No spaces.

After you initially save the configuration, you cannot edit the name.

Ingress Interface

Select the interface that receives traffic.

Egress Interface

Select the interface that forwards traffic.

Source

Select a source address object to use to form the matching tuple.

Destination

Select a destination address object to use to form the matching tuple.

Service

Select a service object to use to form the matching tuple.

Type

Specify whether the limit is per rule or per host.

Side

When the connection limit is per host, specify whether the connection counter gets incremented when the host IP address appears in:

  • Source—Only increment the counter if the host is the source address.
  • Destination—Only increment the counter if the host is the destination address.
  • Both—Increment the counter if the host is the source or destination address.

Limit

Maximum concurrent sessions. The default is 1,048,576.

Reordering

After you have saved a rule, reorder rules as necessary. The rules table is consulted from top to bottom. The first rule that matches is applied and subsequent rules are not evaluated.

Configuring an IPv4 connection limit policy

The firewall connection limit policy allows or denies traffic based on a matching tuple: source address, destination address, and service; and connection count. The purpose is to detect anomalous connection requests.

The limit you specify can be based on the following counts:

  • Count of concurrent sessions that match the tuple.
  • Count of concurrent sessions from a single host that match the tuple.

The FortiADC system evaluates firewall connection limit policy rules before other rules. It matches traffic against the connection limit table, beginning with the first rule. If no rule matches, the connection is forwarded for further processing. If a rule matches, and the limit has not been reached, the connection is forwarded for further processing. If a rule matches and the limit has been reached, the connection is dropped.

By default, if firewall connection limit rules are not configured, the system does not perform connection limit policy processing. The firewall connection limit can be configured for non-SLB traffic and for Layer 7 SLB traffic, but not Layer 4 SLB traffic.

Note: The purpose of the firewall connection limit is distinct from the virtual server connection limit. The firewall connection limit setting is a security setting; the virtual server connection limit is a capacity setting.

Before you begin:

  • You must have a good understanding and knowledge of the capacity of your backend servers.
  • You must have created the address configuration objects and service configuration objects that define the matching tuple in your connection limit rules.
  • You must have Read-Write permission for Firewall settings.
To configure a firewall connection limit:
  1. Click Network Security > Firewall > IPv4 Connection Limit Policy.
  2. Click Create New to display the configuration editor.
  3. Complete the configuration as described in Connection limit configuration.
  4. Save the configuration.
  5. Reorder rules, as necessary.

Connection limit configuration

Settings Guidelines

Name

Configuration name. Valid characters are A-Z, a-z, 0-9, _, and -. No spaces.

After you initially save the configuration, you cannot edit the name.

Ingress Interface

Select the interface that receives traffic.

Egress Interface

Select the interface that forwards traffic.

Source

Select a source address object to use to form the matching tuple.

Destination

Select a destination address object to use to form the matching tuple.

Service

Select a service object to use to form the matching tuple.

Type

Specify whether the limit is per rule or per host.

Side

When the connection limit is per host, specify whether the connection counter gets incremented when the host IP address appears in:

  • Source—Only increment the counter if the host is the source address.
  • Destination—Only increment the counter if the host is the destination address.
  • Both—Increment the counter if the host is the source or destination address.

Limit

Maximum concurrent sessions. The default is 1,048,576.

Reordering

After you have saved a rule, reorder rules as necessary. The rules table is consulted from top to bottom. The first rule that matches is applied and subsequent rules are not evaluated.