Protection Against Distributed Denial of Service Attacks

The Protection Against Distributed Denial of Service Attacks feature provides protection from Denial of Service (DoS) attacks at the global level (for all firewall sessions) and at the VPN routing and forwarding (VRF) level. In Cisco IOS XE Release 3.4S and later releases, you can configure the aggressive aging of firewall sessions, event rate monitoring of firewall sessions, the half-opened connections limit, and global TCP SYN cookie protection to prevent distributed DoS attacks.

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Information About Protection Against Distributed Denial of Service Attacks

Aggressive Aging of Firewall Sessions

The Aggressive Aging feature provides the firewall the capability of aggressively aging out sessions to make room for new sessions, thereby protecting the firewall session database from filling. The firewall protects its resources by removing idle sessions. The Aggressive Aging feature allows firewall sessions to exist for a shorter period of time defined by a timer called aging-out time.

The Aggressive Aging feature includes thresholds to define the start and end of the aggressive aging period—high and low watermarks. The aggressive aging period starts when the session table crosses the high watermark and ends when it falls below the low watermark. During the aggressive aging period, sessions will exist for a shorter period of time that you have configured by using the aging-out time. If an attacker initiates sessions at a rate that is faster than the rate at which the firewall terminates sessions, all resources that are allocated for creating sessions are used and all new connections are rejected. To prevent such attacks, you can configure the Aggressive Aging feature to aggressively age out sessions. This feature is disabled by default.

You can configure aggressive aging for half-opened sessions and total sessions at the box level (box refers to the entire firewall session table) and the virtual routing and forwarding (VRF) level. If you have configured this feature for total sessions, all sessions that consume firewall session resources are taken into account. Total sessions comprise established sessions, half-opened sessions, and sessions in the imprecise session database. (A TCP session that has not yet reached the established state is called a half-opened session.)

A firewall has two session databases: the session database and the imprecise session database. The session database contains sessions with 5-tuple (the source IP address, the destination IP address, the source port, the destination port, and the protocol). A tuple is an ordered list of elements. The imprecise session database contains sessions with fewer than 5-tuple (missing IP addresses, port numbers, and so on). In the case of aggressive aging for half-opened sessions, only half-opened sessions are considered.

You can configure an aggressive aging-out time for Internet Control Message Protocol (ICMP), TCP, and UDP firewall sessions. The aging-out time is set by default to the idle time.

Event Rate Monitoring Feature

The Event Rate Monitoring feature monitors the rate of predefined events in a zone. The Event Rate Monitoring feature includes basic threat detection, which is the ability of a security device to detect possible threats, anomalies, and attacks to resources inside the firewall and to take action against them. You can configure a basic threat detection rate for events. When the incoming rate of a certain type of event exceeds the configured threat detection rate, event rate monitoring considers this event as a threat and takes action to stop the threat. Threat detection inspects events only on the ingress zone (if the Event Rate Monitoring feature is enabled on the ingress zone).

The network administrator is informed about the potential threats via an alert message (syslog or high-speed logger [HSL]) and can take actions such as detecting the attack vector, detecting the zone from which the attack is coming, or configuring devices in the network to block certain behaviors or traffic.

The Event Rate Monitoring feature monitors the following types of events:

  • Firewall drops due to basic firewall checks failure—This can include zone or zone-pair check failures, or firewall policies configured with the drop action, and so on.

  • Firewall drops due to Layer 4 inspection failure—This can include TCP inspections that have failed because the first TCP packet is not a synchronization (SYN) packet.

  • TCP SYN cookie attack—This can include counting the number of SYN packets that are dropped and the number of SYN cookies that are sent as a spoofing attack.

The Event Rate Monitoring feature monitors the average rate and the burst rate of different events. Each event type has a rate object that is controlled by an associated rate that has a configurable parameter set (the average threshold, the burst threshold, and a time period). The time period is divided into time slots; each time slot is 1/30th of the time period.

The average rate is calculated for every event type. Each rate object holds 30 completed sampling values plus one value to hold the current ongoing sampling period. The current sampling value replaces the oldest calculated value and the average is recalculated. The average rate is calculated during every time period. If the average rate exceeds the average threshold, the Event Rate Monitoring feature will consider this as a possible threat, update the statistics, and inform the network administrator.

The burst rate is implemented by using the token bucket algorithm. For each time slot, the token bucket is filled with tokens. For each event that occurs (of a specific event type), a token is removed from the bucket. An empty bucket means that the burst threshold is reached, and the administrator receives an alarm through the syslog or HSL. You can view the threat detection statistics and learn about possible threats to various events in the zone from the output of the show policy-firewall stats zone command.

You must first enable basic threat detection by using the threat-detection basic-threat command. Once basic threat detection is configured, you can configure the threat detection rate. To configure the threat detection rate, use the threat-detection rate command.

The following table describes the basic threat detection default settings that are applicable if the Event Rate Monitoring feature is enabled.

Table 1 Basic Threat Detection Default Settings

Packet Drop Reason

Threat Detection Settings

Basic firewall drops

average-rate 400 packets per second (pps)

burst-rate 1600 pps

rate-interval 600 seconds

Inspection-based firewall drops

average-rate 400 pps

burst-rate 1600 pps

rate-interval 600 seconds

SYN attack firewall drops

average-rate 100 pps

burst-rate 200 pps

rate-interval 600 seconds

Half-Opened Connections Limit

The firewall session table supports the limiting of half-opened firewall connections. Limiting the number of half-opened sessions will defend the firewall against attacks that might fill the firewall session table at the per-box level or at the virtual routing and forwarding (VRF) level with half-opened sessions and prevent sessions from being established. The half-opened connection limit can be configured for Layer 4 protocols, Internet Control Message Protocol (ICMP), TCP, and UDP. The limit set to the number of UDP half-opened sessions will not affect the TCP or ICMP half-opened sessions. When the configured half-opened session limit is exceeded, all new sessions are rejected and a log message is generated, either in syslog or in the high-speed logger (HSL).

The following sessions are considered as half-opened sessions:

  • TCP sessions that have not completed the three-way handshake.

  • UDP sessions that have only one packet detected in the UDP flow.

  • ICMP sessions that do not receive a reply to the ICMP echo request or the ICMP time-stamp request.

TCP SYN-Flood Attacks

You can configure the global TCP SYN-flood limit to limit SYN flood attacks. TCP SYN-flooding attacks are a type of denial of service (DoS) attack. When the configured TCP SYN-flood limit is reached, the firewall verifies the source of sessions before creating more sessions. Usually, TCP SYN packets are sent to a targeted end host or a range of subnet addresses behind the firewall. These TCP SYN packets have spoofed source IP addresses. A spoofing attack is when a person or program tries to use false data to gain access to resources in a network. TCP SYN flooding can take up all resources on a firewall or an end host, thereby causing denial of service to legitimate traffic. You can configure TCP SYN-flood protection at the VRF level and the zone level.

SYN flood attacks are divided into two types:

  • Host flood—SYN flood packets are sent to a single host intending to utilize all resources on that host.

  • Firewall session table flood—SYN flood packets are sent to a range of addresses behind the firewall, with the intention of exhausting the session table resources on the firewall, thereby denying resources to the legitimate traffic going through the firewall.

How to Configure Protection Against Distributed Denial of Service Attacks

Configuring a Firewall

In this task, you will do the following:

  • Configure a firewall.

  • Create a security source zone.

  • Create a security destination zone.

  • Create a security zone pair by using the configured source and destination zones.

  • Configure an interface as a zone member.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    class-map type inspect match-any class-map-name

    4.    match protocol {icmp | tcp | udp}

    5.    exit

    6.    parameter-map type inspect global

    7.    redundancy

    8.    exit

    9.    policy-map type inspect policy-map-name

    10.    class type inspect class-map-name

    11.    inspect

    12.    exit

    13.    class class-default

    14.    drop

    15.    exit

    16.    exit

    17.    zone security security-zone-name

    18.    exit

    19.    zone security security-zone-name

    20.    exit

    21.    zone-pair security zone-pair-name source source-zone destination destination-zone

    22.    service-policy type inspect policy-map-name

    23.    exit

    24.    interface type number

    25.    ip address ip-address mask

    26.    encapsulation dot1q vlan-id

    27.    zone-member security security-zone-name

    28.    end

    29.    To attach a zone to another interface, repeat Steps 21 to 25.


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3class-map type inspect match-any class-map-name


    Example:
    Device(config)# class-map type inspect match-any ddos-class
     

    Creates an application-specific inspect type class map and enters QoS class-map configuration mode.

     
    Step 4match protocol {icmp | tcp | udp}


    Example:
    Device(config-cmap)# match protocol tcp
     

    Configures the match criterion for a class map based on the specified protocol.

     
    Step 5exit


    Example:
    Device(config-cmap)# exit
     

    Exits QoS class-map configuration mode and enters global configuration mode.

     
    Step 6parameter-map type inspect global


    Example:
    Device(config)# parameter-map type inspect global
     

    Defines a global inspect parameter map and enters parameter-map type inspect configuration mode.

     
    Step 7redundancy


    Example:
    Device(config-profile)# redundancy
     

    Enables firewall high availability.

     
    Step 8exit


    Example:
    Device(config-profile)# exit
     

    Exits parameter-map type inspect configuration mode and enters global configuration mode.

     
    Step 9policy-map type inspect policy-map-name


    Example:
    Device(config)# policy-map type inspect ddos-fw
     

    Creates a protocol-specific inspect type policy map and enters QoS policy-map configuration mode.

     
    Step 10class type inspect class-map-name


    Example:
    Device(config-pmap)# class type inspect ddos-class
     

    Specifies the traffic class on which an action is to be performed and enters QoS policy-map class configuration mode.

     
    Step 11inspect


    Example:
    Device(config-pmap-c)# inspect
     

    Enables stateful packet inspection.

     
    Step 12exit


    Example:
    Device(config-pmap-c)# exit
     

    Exits QoS policy-map class configuration mode and enters QoS policy-map configuration mode.

     
    Step 13class class-default


    Example:
    Device(config-pmap)# class class-default
     

    Configures the default class on which an action is to be performed and enters QoS policy-map class configuration mode.

     
    Step 14drop


    Example:
    Device(config-pmap-c)# drop
     

    Allows traffic to pass between two interfaces in the same zone.

     
    Step 15exit


    Example:
    Device(config-pmap-c)# exit
     

    Exits QoS policy-map class configuration mode and enters QoS policy-map configuration mode.

     
    Step 16exit


    Example:
    Device(config-pmap)# exit
     

    Exits QoS policy-map configuration mode and enters global configuration mode.

     
    Step 17zone security security-zone-name


    Example:
    Device(config)# zone security private
     
    Creates a security zone and enters security zone configuration mode.

    • You need two security zones to create a zone pair—a source and a destination zone.

     
    Step 18exit


    Example:
    Device(config-sec-zone)# exit
     

    Exits security zone configuration mode and enters global configuration mode.

     
    Step 19zone security security-zone-name


    Example:
    Device(config)# zone security public
     
    Creates a security zone and enters security zone configuration mode.

    • You need two security zones to create a zone pair—a source and a destination zone.

     
    Step 20exit


    Example:
    Device(config-sec-zone)# exit
     

    Exits security zone configuration mode and enters global configuration mode.

     
    Step 21zone-pair security zone-pair-name source source-zone destination destination-zone


    Example:
    Device(config)# zone-pair security private2public source private destination public
     

    Creates a zone pair and enters security zone-pair configuration mode.

     
    Step 22service-policy type inspect policy-map-name


    Example:
    Device(config-sec-zone-pair)# service-policy type inspect ddos-fw
     

    Attaches a policy map to a top-level policy map.

     
    Step 23exit


    Example:
    Device(config-sec-zone-pair)# exit
     

    Exits security zone-pair configuration mode and enters global configuration mode.

     
    Step 24interface type number


    Example:
    Device(config)# interface gigabitethernet 0/1/0.1
     

    Configures an interface and enters subinterface configuration mode.

     
    Step 25ip address ip-address mask


    Example:
    Device(config-subif)# ip address 10.1.1.1 255.255.255.0
     

    Configures an IP address for the subinterface.

     
    Step 26encapsulation dot1q vlan-id


    Example:
    Device(config-subif)# encapsulation dot1q 2
     

    Sets the encapsulation method used by the interface.

     
    Step 27zone-member security security-zone-name


    Example:
    Device(config-subif)# zone-member security private
     

    Configures the interface as a zone member.

    • For the security-zone-name argument, you must configure one of the zones that you had configured by using the zone security command.

    • When an interface is in a security zone, all traffic to and from that interface (except traffic going to the device or initiated by the device) is dropped by default. To permit traffic through an interface that is a zone member, you must make that zone part of a zone pair to which you apply a policy. If the policy permits traffic (via inspect or pass actions), traffic can flow through the interface.

     
    Step 28end


    Example:
    Device(config-subif)# end
     

    Exits subinterface configuration mode and enters privileged EXEC mode.

     
    Step 29To attach a zone to another interface, repeat Steps 21 to 25.  

    —

     

    Configuring the Aggressive Aging of Firewall Sessions

    You can configure the Aggressive Aging feature for per-box (per-box refers to the entire firewall session table), default-VRF, and per-VRF firewall sessions. Before the Aggressive Aging feature can work, you must configure the aggressive aging and the aging-out time of firewall sessions.

    Perform the following tasks to configure the aggressive aging of firewall sessions.

    Configuring per-Box Aggressive Aging

    Per-box refers to the entire firewall session table. Any configuration that follows the parameter-map type inspect-global command applies to the box.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    Enter one of the following commands:

      • parameter-map type inspect-global
      • parameter-map type inspect global

      4.    per-box max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}

      5.    per-box aggressive-aging high {value low value | percent percent low percent percent}

      6.    exit

      7.    parameter-map type inspect parameter-map-name

      8.    tcp synwait-time seconds [ageout-time seconds]

      9.    end

      10.    show policy-firewall stats global


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3Enter one of the following commands:
      • parameter-map type inspect-global
      • parameter-map type inspect global


      Example:
      Device(config)# parameter-map type inspect-global
      Device(config)# parameter-map type inspect global
       
      Configures a global parameter map for connecting thresholds and timeouts and enters parameter-map type inspect configuration mode.

      • Based on your release, the parameter-map type inspect-global and the parameter-map type inspect global commands are supported. You cannot configure both these commands together.

      • Skip Steps 4 and 5 if you configure the parameter-map type inspect-global command.

      Note   

      If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

       
      Step 4per-box max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}


      Example:
      Device(config-profile)# per-box max-incomplete 2000 aggressive-aging high 1500 low 1200
       

      Configures the maximum limit and the aggressive aging rate for half-opened sessions in the firewall session table.

       
      Step 5per-box aggressive-aging high {value low value | percent percent low percent percent}


      Example:
      Device(config-profile)# per-box aggressive-aging high 1700 low 1300
       

      Configures the aggressive aging limit of total sessions.

       
      Step 6exit


      Example:
      Device(config-profile)# exit
       

      Exits parameter-map type inspect configuration mode and enters global configuration mode.

       
      Step 7parameter-map type inspect parameter-map-name


      Example:
      Device(config)# parameter-map type inspect pmap1
       

      Configures an inspect-type parameter map for connecting thresholds, timeouts, and other parameters pertaining to the inspect action and enters parameter-map type inspect configuration mode.

       
      Step 8tcp synwait-time seconds [ageout-time seconds]


      Example:
      Device(config-profile)# tcp synwait-time 30 ageout-time 10
       

      Specifies how long the software will wait for a TCP session to reach the established state before dropping the session.

      • After aggressive aging is enabled, the SYN wait timer of the oldest TCP connections are reset from the default to the configured ageout time. In this example, instead of waiting for 30 seconds for connections to timeout, the timeout of the oldest TCP connections are set to 10 seconds. Aggressive aging is disabled when the connections drop below the low watermark.

       
      Step 9end


      Example:
      Device(config-profile)# end
       

      Exits parameter-map type inspect configuration mode and enters privileged EXEC mode.

       
      Step 10show policy-firewall stats global


      Example:
      Device# show policy-firewall stats global
       

      Displays global firewall statistics information.

       

      Configuring Aggressive Aging for a Default VRF

      When you configure the max-incomplete aggressive-aging command, it applies to the default VRF.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    Enters one of the following commands:

        • parameter-map type inspect-global
        • parameter-map type inspect global

        4.    max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}

        5.    session total number [aggressive-aging high {value low value | percent percent low percent percent}]

        6.    exit

        7.    parameter-map type inspect parameter-map-name

        8.    tcp synwait-time seconds [ageout-time seconds]

        9.    end

        10.    show policy-firewall stats vrf global


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3Enters one of the following commands:
        • parameter-map type inspect-global
        • parameter-map type inspect global


        Example:
        Device(config)# parameter-map type inspect-global
        Device(config)# parameter-map type inspect global
         
        Configures a global parameter map for connecting thresholds and timeouts and enters parameter-map type inspect configuration mode.

        • Based on your release, the parameter-map type inspect-global and the parameter-map type inspect global commands are supported. You cannot configure both these commands together.

        • Skip Step 5 if you configure the parameter-map type inspect-global command.

        Note   

        If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

         
        Step 4max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}


        Example:
        Device(config-profile)# max-incomplete 3455 aggressive-aging high 2345 low 2255
         

        Configures the maximum limit and the aggressive aging limit of half-opened firewall sessions.

         
        Step 5session total number [aggressive-aging high {value low value | percent percent low percent percent}]


        Example:
        Device(config-profile)# session total 1000 aggressive-aging high percent 80 low percent 60
         

        Configures the total limit and the aggressive aging limit for total firewall sessions.

         
        Step 6exit


        Example:
        Device(config-profile)# exit
         

        Exits parameter-map type inspect configuration mode and enters global configuration mode.

         
        Step 7parameter-map type inspect parameter-map-name


        Example:
        Device(config)# parameter-map type inspect pmap1
         

        Configures an inspect-type parameter map for connecting thresholds, timeouts, and other parameters pertaining to the inspect action and enters parameter-map type inspect configuration mode.

         
        Step 8tcp synwait-time seconds [ageout-time seconds]


        Example:
        Device(config-profile)# tcp synwait-time 30 ageout-time 10
         

        Specifies how long the software will wait for a TCP session to reach the established state before dropping the session.

        • After aggressive aging is enabled, the SYN wait timer of the oldest TCP connections are reset from the default to the configured ageout time. In this example, instead of waiting for 30 seconds for connections to timeout, the timeout of the oldest TCP connections are set to 10 seconds. Aggressive aging is disabled when the connections drop below the low watermark.

         
        Step 9end


        Example:
        Device(config-profile)# end
         

        Exits parameter-map type inspect configuration mode and enters privileged EXEC mode.

         
        Step 10show policy-firewall stats vrf global


        Example:
        Device# show policy-firewall stats vrf global
         

        Displays global VRF firewall policy statistics.

         

        Configuring the Aging Out of Firewall Sessions

        You can configure the aging out of ICMP, TCP, or UDP firewall sessions.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    Enter one of the following commands:

          • parameter-map type inspect-global
          • parameter-map type inspect global

          4.    vrf vrf-name inspect vrf-pmap-name

          5.    exit

          6.    parameter-map type inspect parameter-map-name

          7.    tcp idle-time seconds [ageout-time seconds]

          8.    tcp synwait-time seconds [ageout-time seconds]

          9.    exit

          10.    policy-map type inspect policy-map-name

          11.    class type inspect match-any class-map-name

          12.    inspect parameter-map-name

          13.    end

          14.    show policy-firewall stats vrf vrf-pmap-name


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2configure terminal


          Example:
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3Enter one of the following commands:
          • parameter-map type inspect-global
          • parameter-map type inspect global


          Example:
          Device(config)# parameter-map type inspect-global
          Device(config)# parameter-map type inspectglobal
           
          Configures a global parameter map and enters parameter-map type inspect configuration mode.

          • Based on your release, the parameter-map type inspect-global and the parameter-map type inspect global commands are supported. You cannot configure both these commands together.

          • Skip Step 4 if you configure the parameter-map type inspect-global command.

          Note   

          If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

           
          Step 4vrf vrf-name inspect vrf-pmap-name


          Example:
          Device(config-profile)# vrf vrf1 inspect vrf1-pmap
           

          Binds a VRF with a parameter map.

           
          Step 5exit


          Example:
          Device(config-profile)# exit
           

          Exits parameter-map type inspect configuration mode and enters global configuration mode.

           
          Step 6parameter-map type inspect parameter-map-name


          Example:
          Device(config)# parameter-map type inspect pmap1
           

          Configures an inspect-type parameter map for connecting thresholds, timeouts, and other parameters pertaining to the inspect action and enters parameter-map type inspect configuration mode.

           
          Step 7tcp idle-time seconds [ageout-time seconds]


          Example:
          Device(config-profile)# tcp idle-time 3000 ageout-time 100
           
          Configures the timeout for idle TCP sessions and the aggressive aging-out time for TCP sessions.

          • You can also configure the tcp finwait-time command to specify how long a TCP session will be managed after the firewall detects a finish (FIN) exchange, or you can configure the tcp synwait-time command to specify how long the software will wait for a TCP session to reach the established state before dropping the session.

           
          Step 8tcp synwait-time seconds [ageout-time seconds]


          Example:
          Device(config-profile)# tcp synwait-time 30 ageout-time 10
           

          Specifies how long the software will wait for a TCP session to reach the established state before dropping the session.

          • When aggressive aging is enabled, the SYN wait timer of the oldest TCP connections are reset from the default to the configured ageout time. In this example, instead of waiting for 30 seconds for connections to timeout, the timeout of the oldest TCP connections are set to 10 seconds. Aggressive aging is enabled when the connections drop below the low watermark.

           
          Step 9exit


          Example:
          Device(config-profile)# exit
           

          Exits parameter-map type inspect configuration mode and enters global configuration mode.

           
          Step 10policy-map type inspect policy-map-name


          Example:
          Device(config)# policy-map type inspect ddos-fw
           

          Creates a protocol-specific inspect type policy map and enters QoS policy-map configuration mode.

           
          Step 11class type inspect match-any class-map-name


          Example:
          Device(config-pmap)# class type inspect match-any ddos-class
           

          Specifies the traffic class on which an action is to be performed and enters QoS policy-map class configuration mode.

           
          Step 12inspect parameter-map-name


          Example:
          Device(config-pmap-c)# inspect pmap1
           

          Enables stateful packet inspection for the parameter map.

           
          Step 13end


          Example:
          Device(config-pmap-c)# end
           

          Exits QoS policy-map class configuration mode and enters privileged EXEC mode.

           
          Step 14show policy-firewall stats vrf vrf-pmap-name


          Example:
          Device# show policy-firewall stats vrf vrf1-pmap
           

          Displays VRF-level policy firewall statistics.

           
          Example

          The following is sample output from the show policy-firewall stats vrf vrf1-pmap command: 

          Device# show policy-firewall stats vrf vrf1-pmap

 VRF: vrf1, Parameter-Map: vrf1-pmap
  Interface reference count: 2
       Total Session Count(estab + half-open): 270, Exceed: 0
       Total Session Aggressive Aging Period Off, Event Count: 0

                Half Open
       Protocol Session Cnt     Exceed
       -------- -----------     ------
       All      0               0
       UDP      0               0
       ICMP     0               0
       TCP      0               0

       TCP Syn Flood Half Open Count: 0, Exceed: 12       
       Half Open Aggressive Aging Period Off, Event Count: 0

          Configuring per-VRF Aggressive Aging

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    ip vrf vrf-name

            4.    rd route-distinguisher

            5.    route-target export route-target-ext-community

            6.    route-target import route-target-ext-community

            7.    exit

            8.    parameter-map type inspect-vrf vrf-pmap-name

            9.    max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}

            10.    session total number [aggressive-aging {high value low value | percent percent low percent percent}]

            11.    alert on

            12.    exit

            13.    Enter one of the following commands:

            • parameter-map type inspect-global
            • parameter-map type inspect global

            14.    vrf vrf-name inspect vrf-pmap-name

            15.    exit

            16.    parameter-map type inspect parameter-map-name

            17.    tcp idle-time seconds [ageout-time seconds]

            18.    tcp synwait-time seconds [ageout-time seconds]

            19.    exit

            20.    policy-map type inspect policy-map-name

            21.    class type inspect match-any class-map-name

            22.    inspect parameter-map-name

            23.    end

            24.    show policy-firewall stats vrf vrf-pmap-name


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Device> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.

             
            Step 2configure terminal


            Example:
            Device# configure terminal
             

            Enters global configuration mode.

             
            Step 3ip vrf vrf-name


            Example:
            Device(config)# ip vrf ddos-vrf1
             

            Defines a VRF instance and enters VRF configuration mode.

             
            Step 4rd route-distinguisher


            Example:
            Device(config-vrf)# rd 100:2
             

            Specifies a route distinguisher (RD) for a VRF instance.

             
            Step 5route-target export route-target-ext-community


            Example:
            Device(config-vrf)# route-target export 100:2
             

            Creates a route-target extended community and exports the routing information to the target VPN extended community.

             
            Step 6route-target import route-target-ext-community


            Example:
            Device(config-vrf)# route-target import 100:2
             

            Creates a route-target extended community and imports routing information from the target VPN extended community.

             
            Step 7exit


            Example:
            Device(config-vrf)# exit
             

            Exits VRF configuration mode and enters global configuration mode.

             
            Step 8parameter-map type inspect-vrf vrf-pmap-name


            Example:
            Device(config)# parameter-map type inspect-vrf vrf1-pmap
             

            Configures an inspect VRF-type parameter map and enters parameter-map type inspect configuration mode.

             
            Step 9max-incomplete number aggressive-aging high {value low value | percent percent low percent percent}


            Example:
            Device(config-profile)# max-incomplete 2000 aggressive-aging high 1500 low 1200
             

            Configures the maximum limit and the aggressive aging limit for half-opened sessions.

             
            Step 10session total number [aggressive-aging {high value low value | percent percent low percent percent}]


            Example:
            Device(config-profile)# session total 1000 aggressive-aging high percent 80 low percent 60
             

            Configures the total session limit and the aggressive aging limit for the total sessions.

            • You can configure the total session limit as an absolute value or as a percentage.

             
            Step 11alert on


            Example:
            Device(config-profile)# alert on
             

            Enables the console display of stateful packet inspection alert messages.

             
            Step 12exit


            Example:
            Device(config-profile)# exit
             

            Exits parameter-map type inspect configuration mode and enters global configuration mode.

             
            Step 13Enter one of the following commands:
            • parameter-map type inspect-global
            • parameter-map type inspect global


            Example:
            Device(config)# parameter-map type inspect-global
            Device(config)# parameter-map type inspect global
             
            Configures a global parameter map and enters parameter-map type inspect configuration mode.

            • Based on your release, the parameter-map type inspect-global and the parameter-map type inspect global commands are supported. You cannot configure both these commands together.

            • Skip Step 14 if you configure the parameter-map type inspect-global command.

            Note   

            If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

             
            Step 14vrf vrf-name inspect vrf-pmap-name


            Example:
            Device(config-profile)# vrf vrf1 inspect vrf1-pmap
             

            Binds a VRF with a parameter map.

             
            Step 15exit


            Example:
            Device(config-profile)# exit
             

            Exits parameter-map type inspect configuration mode and enters global configuration mode.

             
            Step 16parameter-map type inspect parameter-map-name


            Example:
            Device(config)# parameter-map type inspect pmap1
             

            Configures an inspect-type parameter map for connecting thresholds, timeouts, and other parameters pertaining to the inspect action and enters parameter-map type inspect configuration mode.

             
            Step 17tcp idle-time seconds [ageout-time seconds]


            Example:
            Device(config-profile)# tcp idle-time 3000 ageout-time 100
             

            Configures the timeout for idle TCP sessions and the aggressive aging-out time for TCP sessions.

             
            Step 18tcp synwait-time seconds [ageout-time seconds]


            Example:
            Device(config-profile)# tcp synwait-time 30 ageout-time 10
             

            Specifies how long the software will wait for a TCP session to reach the established state before dropping the session.

            • When aggressive aging is enabled, the SYN wait timer of the oldest TCP connections are reset from the default to the configured ageout time. In this example, instead of waiting for 30 seconds for connections to timeout, the timeout of the oldest TCP connections are set to 10 seconds. Aggressive aging is disabled when the connections drop below the low watermark.

             
            Step 19exit


            Example:
            Device(config-profile)# exit
             

            Exits parameter-map type inspect configuration mode and enters global configuration mode.

             
            Step 20policy-map type inspect policy-map-name


            Example:
            Device(config)# policy-map type inspect ddos-fw
             

            Creates a protocol-specific inspect type policy map and enters QoS policy-map configuration mode.

             
            Step 21class type inspect match-any class-map-name


            Example:
            Device(config-pmap)# class type inspect match-any ddos-class
             

            Specifies the traffic (class) on which an action is to be performed and enters QoS policy-map class configuration mode.

             
            Step 22inspect parameter-map-name


            Example:
            Device(config-pmap-c)# inspect pmap1
             

            Enables stateful packet inspection for the parameter map.

             
            Step 23end


            Example:
            Device(config-pmap-c)# end
             

            Exits QoS policy-map class configuration mode and enters privileged EXEC mode.

             
            Step 24show policy-firewall stats vrf vrf-pmap-name


            Example:
            Device# show policy-firewall stats vrf vrf1-pmap
             

            Displays VRF-level policy firewall statistics.

             
            Example

            The following is sample output from the show policy-firewall stats vrf vrf1-pmap command: 

            Device# show policy-firewall stats vrf vrf1-pmap

VRF: vrf1, Parameter-Map: vrf1-pmap
  Interface reference count: 2
       Total Session Count(estab + half-open): 80, Exceed: 0
       Total Session Aggressive Aging Period Off, Event Count: 0

                Half Open
       Protocol Session Cnt     Exceed
       -------- -----------     ------
       All      0               0
       UDP      0               0
       ICMP     0               0
       TCP      0               0

       TCP Syn Flood Half Open Count: 0, Exceed: 116
       Half Open Aggressive Aging Period Off, Event Count: 0

            Configuring Firewall Event Rate Monitoring

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    parameter-map type inspect-zone zone-pmap-name

              4.    alert on

              5.    threat-detection basic-threat

              6.    threat-detection rate fw-drop average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second

              7.    threat-detection rate inspect-drop average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second

              8.    threat-detection rate syn-attack average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second

              9.    exit

              10.    zone security security-zone-name

              11.    protection parameter-map-name

              12.    exit

              13.    zone-pair security zone-pair-name source source-zone destination destination-zone

              14.    end

              15.    show policy-firewall stats zone


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Device> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.

               
              Step 2configure terminal


              Example:
              Device# configure terminal
               

              Enters global configuration mode.

               
              Step 3parameter-map type inspect-zone zone-pmap-name


              Example:
              Device(config)# parameter-map type inspect-zone zone-pmap1
               

              Configures an inspect-zone parameter map and enters parameter-map type inspect configuration mode.

               
              Step 4alert on


              Example:
              Device(config-profile)# alert on
               
              Enables the console display of stateful packet inspection alert messages for a zone.

              • You can use the log command to configure the logging of alerts either to the syslog or to the high-speed logger (HSL).

               
              Step 5threat-detection basic-threat


              Example:
              Device(config-profile)# threat-detection basic-threat
               

              Configures basic threat detection for a zone.

               
              Step 6threat-detection rate fw-drop average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second


              Example:
              Device(config-profile)# threat-detection rate fw-drop average-time-frame 600 average-threshold 100 burst-threshold 100
               
              Configures the threat detection rate for firewall drop events.

              • You must configure the threat-detection basic-threat command before you configure the threat-detection rate command.

               
              Step 7threat-detection rate inspect-drop average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second


              Example:
              Device(config-profile)# threat-detection rate inspect-drop average-time-frame 600 average-threshold 100 burst-threshold 100
               

              Configures the threat detection rate for firewall inspection-based drop events.

               
              Step 8threat-detection rate syn-attack average-time-frame seconds average-threshold packets-per-second burst-threshold packets-per-second


              Example:
              Device(config-profile)# threat-detection rate syn-attack average-time-frame 600 average-threshold 100 burst-threshold 100
               

              Configures the threat detection rate for TCP SYN attack events.

               
              Step 9exit


              Example:
              Device(config-profile)# exit
               

              Exits parameter-map type inspect configuration mode and enters global configuration mode.

               
              Step 10zone security security-zone-name


              Example:
              Device(config)# zone security public
               

              Creates a security zone and enters security zone configuration mode.

               
              Step 11protection parameter-map-name


              Example:
              Device(config-sec-zone)# protection zone-pmap1
               

              Attaches the inspect-zone parameter map to the zone and applies the features configured in the inspect-zone parameter map to the zone.

               
              Step 12exit


              Example:
              Device(config-sec-zone)# exit
               

              Exits security zone configuration mode and enters global configuration mode.

               
              Step 13zone-pair security zone-pair-name source source-zone destination destination-zone


              Example:
              Device(config)# zone-pair security private2public source private destination public
               

              Creates a zone pair and enters security zone-pair configuration mode.

               
              Step 14end


              Example:
              Device(config-sec-zone-pair)# end
               

              Exits security zone-pair configuration mode and enters privileged EXEC mode.

               
              Step 15show policy-firewall stats zone


              Example:
              Device# show policy-firewall stats zone
               

              Displays policy firewall statistics at the zone level.

               

              Configuring the per-Box Half-Opened Session Limit

              Per-box refers to the entire firewall session table. Any configuration that follows the parameter-map type inspect-global command applies to the box.

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    Enter one of the following commands:

                • parameter-map type inspect-global
                • parameter-map type inspect global

                4.    alert on

                5.    per-box max-incomplete number

                6.    session total number

                7.    end

                8.    show policy-firewall stats global


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example:
                Device> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.

                 
                Step 2configure terminal


                Example:
                Device# configure terminal
                 

                Enters global configuration mode.

                 
                Step 3Enter one of the following commands:
                • parameter-map type inspect-global
                • parameter-map type inspect global


                Example:
                Device(config)# parameter-map type inspect-global
                Device(config)# parameter-map type inspect global
                 

                Configures a global parameter map for connecting thresholds and timeouts and enters parameter-map type inspect configuration mode.

                • Based on your release, the parameter-map type inspect-global and the parameter-map type inspect global commands are supported. You cannot configure both these commands together.

                • Skip to Steps 5 and 6 if you configure the parameter-map type inspect-global command.

                Note   

                If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

                 
                Step 4alert on


                Example:
                Device(config-profile)# alert on
                 

                Enables the console display of stateful packet inspection alert messages.

                 
                Step 5per-box max-incomplete number


                Example:
                Device(config-profile)# per-box max-incomplete 12345
                 

                Configures the maximum number of half-opened connections for the firewall session table.

                 
                Step 6session total number


                Example:
                Device(config-profile)# session total 34500
                 

                Configures the total session limit for the firewall session table.

                 
                Step 7end


                Example:
                Device(config-profile)# end
                 

                Exits parameter-map type inspect configuration mode and enters privileged EXEC mode.

                 
                Step 8show policy-firewall stats global


                Example:
                Device# show policy-firewall stats global
                 

                Displays global firewall statistics information.

                 

                Configuring the Half-Opened Session Limit for an Inspect-VRF Parameter Map

                SUMMARY STEPS

                  1.    enable

                  2.    configure terminal

                  3.    parameter-map type inspect-vrf vrf-name

                  4.    alert on

                  5.    max-incomplete number

                  6.    session total number

                  7.    exit

                  8.    Enter one of the following commands:

                  • parameter-map type inspect-global
                  • parameter-map type inspect global

                  9.    alert on

                  10.    vrf vrf-name inspect vrf-pmap-name

                  11.    end

                  12.    show policy-firewall stats vrf vrf-pmap-name


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1 enable


                  Example:
                  Device> enable
                   

                  Enables privileged EXEC mode.

                  • Enter your password if prompted.

                   
                  Step 2configure terminal


                  Example:
                  Device# configure terminal
                   

                  Enters global configuration mode.

                   
                  Step 3parameter-map type inspect-vrf vrf-name


                  Example:
                  Device(config)# parameter-map type inspect-vrf vrf1-pmap
                   

                  Configures an inspect-VRF parameter map and enters parameter-map type inspect configuration mode.

                   
                  Step 4alert on


                  Example:
                  Device(config-profile)# alert on
                   

                  Enables the console display of stateful packet inspection alert messages.

                   
                  Step 5max-incomplete number


                  Example:
                  Device(config-profile)# max-incomplete 2000
                   

                  Configures the maximum number of half-opened connections per VRF.

                   
                  Step 6session total number


                  Example:
                  Device(config-profile)# session total 34500
                   

                  Configures the total session limit for a VRF.

                   
                  Step 7exit


                  Example:
                  Device(config-profile)# exit
                   

                  Exits parameter-map type inspect configuration mode and enters global configuration mode.

                   
                  Step 8Enter one of the following commands:
                  • parameter-map type inspect-global
                  • parameter-map type inspect global


                  Example:
                  Device(config)# parameter-map type inspect-global
                  Device(config)# parameter-map type inspect global
                   
                  Configures a global parameter map for connecting thresholds and timeouts and enters parameter-map type inspect configuration mode.

                  • Based on your release, you can use either the parameter-map type inspect-global command or the parameter-map type inspect global command. You cannot configure both these commands together.

                  • Skip Step 10 if you configure the parameter-map type inspect-global command.

                  Note   

                  If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

                   
                  Step 9alert on


                  Example:
                  Device(config-profile)# alert on
                   

                  Enables the console display of stateful packet inspection alert messages.

                   
                  Step 10vrf vrf-name inspect vrf-pmap-name


                  Example:
                  Device(config-profile)# vrf vrf1 inspect vrf1-pmap
                   

                  Binds the VRF to the global parameter map.

                   
                  Step 11end


                  Example:
                  Device(config-profile)# end
                   

                  Exits parameter-map type inspect configuration mode and enters privileged EXEC mode.

                   
                  Step 12show policy-firewall stats vrf vrf-pmap-name


                  Example:
                  Device# show policy-firewall stats vrf vrf1-pmap
                   

                  Displays VRF-level policy firewall statistics.

                   

                  Configuring the Global TCP SYN Flood Limit

                  SUMMARY STEPS

                    1.    enable

                    2.    configure terminal

                    3.    Enter one of the following commands:

                    • parameter-map type inspect-global
                    • parameter-map type inspect global

                    4.    alert on

                    5.    per-box tcp syn-flood limit number

                    6.    end

                    7.    show policy-firewall stats vrf global


                  DETAILED STEPS
                     Command or ActionPurpose
                    Step 1 enable


                    Example:
                    Device> enable
                     

                    Enables privileged EXEC mode.

                    • Enter your password if prompted.

                     
                    Step 2 configure terminal


                    Example:
                    Device# configure terminal
                     

                    Enters global configuration mode.

                     
                    Step 3Enter one of the following commands:
                    • parameter-map type inspect-global
                    • parameter-map type inspect global


                    Example:
                    Device(config)# parameter-map type inspect-global
                    Device(config)# parameter-map type inspect global
                     

                    Configures a global parameter map and enters parameter-map type inspect configuration mode.

                    • Based on your release, you can configure either the parameter-map type inspect-global command or the parameter-map type inspect global command. You cannot configure both these commands together.

                    • Skip Step 5 if you configure the parameter-map type inspect-global command.

                    Note   

                    If you configure the parameter-map type inspect-global command, per-box configurations are not supported because, by default, all per-box configurations apply to all firewall sessions.

                     
                    Step 4 alert on


                    Example:
                    Device(config-profile)# alert on
                     

                    Enables the console display of stateful packet inspection alert messages.

                     
                    Step 5 per-box tcp syn-flood limit number


                    Example:
                    Device(config-profile)# per-box tcp syn-flood limit 500
                     

                    Limits the number of TCP half-opened sessions that trigger SYN cookie processing for new SYN packets.

                     
                    Step 6 end


                    Example:
                    Device(config-profile)# end
                     

                    Exits parameter-map type inspect configuration mode and enters privileged EXEC mode.

                     
                    Step 7 show policy-firewall stats vrf global


                    Example:
                    Device# show policy-firewall stats vrf global
                     

                    (Optional) Displays the status of the global VRF firewall policy.

                    • The command output also displays how many TCP half-opened sessions are present.

                     

                    Example

                    The following is sample output from the show policy-firewall stats vrf global command: 

                    Device# show policy-firewall stats vrf global
 
Global table statistics
       total_session_cnt: 0
       exceed_cnt:        0
       tcp_half_open_cnt: 0
       syn_exceed_cnt:    0

                    Configuration Examples for Protection Against Distributed Denial of Service Attacks

                    Example: Configuring a Firewall

                    Router# configure terminal
Router(config)# class-map type inspect match-any ddos-class
Router(config-cmap)# match protocol tcp
Router(config-cmap-c)# exit
Router(config)# parameter-map type inspect global
Router(config-profile)# redundancy
Router(config-profile)# exit
Router(config)# policy-map type inspect ddos-fw
Router(config-pmap)# class type inspect ddos-class
Router(config-pmap-c)# inspect
Router(config-pmap-c)# exit
Router(config-pmap)# class class-default
Router(config-pmap-c)# drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
Router(config)# zone security private
Router(config-sec-zone)# exit
Router(config)# zone security public
Router(config-sec-zone)# exit
Router(config)# zone-pair security private2public source private destination public
Router((config-sec-zone-pair)# service-policy type inspect ddos-fw
Router((config-sec-zone-pair)# exit
Router(config)# interface gigabitethernet 0/1/0.1
Router(config-subif)# ip address 10.1.1.1 255.255.255.0
Router(config-subif)# encapsulation dot1q 2
Router(config-subif)# zone-member security private
Router(config-subif)# exit
Router(config)# interface gigabitethernet 1/1/0.1
Router(config-subif)# ip address 10.2.2.2 255.255.255.0
Router(config-subif)# encapsulation dot1q 2
Router(config-subif)# zone-member security public
Router(config-subif)# end

                    Example: Configuring the Aggressive Aging of Firewall Sessions

                    Example: Configuring per-Box Aggressive Aging

                    Device# configure terminal
Device(config)# parameter-map type inspect global
Device(config-profile)# per-box max-incomplete 2000 aggressive-aging 1500 low 1200
Device(config-profile)# per-box aggressive-aging high 1700 low 1300
Device(config-profile)# exit
Device(config)# parameter-map type inspect pmap1
Device(config-profile)# tcp synwait-time 30 ageout-time 10
Device(config-profile)# end

                    Example: Configuring Aggressive Aging for a Default VRF

                    Device# configure terminal
Device(config)# parameter-map type inspect global
Device(config-profile)# max-incomplete 2000 aggressive-aging high 1500 low 1200
Device(config-profile)# session total 1000 aggressive-aging high percent 80 low percent 60
Device(config-profile)# exit
Device(config)# parameter-map type inspect pmap1
Device(config-profile)# tcp synwait-time 30 ageout-time 10
Device(config-profile)# end

                    Example: Configuring the Aging Out of Firewall Sessions

                    Device# configure terminal
Device(config-profile)# exit
Device(config)# parameter-map type inspect global
Device(config-profile)# vrf vrf1 inspect vrf1-pmap
Device(config-profile)# exit
Device(config)# parameter-map type inspect pmap1
Device(config-profile)# tcp idle-time 3000 ageout-time 100
Device(config-profile)# tcp synwait-time 30 ageout-time 10
Device(config-profile)# exit
Device(config)# policy-map type inspect ddos-fw
Device(config-profile)# class type inspect match-any ddos-class
Device(config-profile)# inspect pmap1
Device(config-profile)# end

                    Example: Configuring per-VRF Aggressive Aging

                    Device# configure terminal
Device(config)# ip vrf ddos-vrf1
Device(config-vrf)# rd 100:2
Device(config-vrf)# route-target export 100:2
Device(config-vrf)# route-target import 100:2
Device(config-vrf)# exit
Device(config)# parameter-map type inspect-vrf vrf1-pmap
Device(config-profile)# max-incomplete 3455 aggressive-aging high 2345 low 2255
Device(config-profile)# session total 1000 aggressive-aging high percent 80 low percent 60
Device(config-profile)# alert on
Device(config-profile)# exit
Device(config)# parameter-map type inspect global
Device(config-profile)# vrf vrf1 inspect vrf1-pmap
Device(config-profile)# exit
Device(config)# parameter-map type inspect pmap1
Device(config-profile)# tcp idle-time 3000 ageout-time 100
Device(config-profile)# tcp synwait-time 30 ageout-time 10
Device(config-profile)# exit
Device(config)# policy-map type inspect ddos-fw
Device(config-pmap)# class type inspect match-any ddos-class
Device(config-pmap-c)# inspect pmap1
Device(config-profile)# end

                    Example: Configuring Firewall Event Rate Monitoring

                    Device> enable
Device# configure terminal
Device(config)# parameter-map type inspect zone zone-pmap1
Device(config-profile)# alert on
Device(config-profile)# threat-detection basic-threat
Device(config-profile)# threat-detection rate fw-drop average-time-frame 600 average-threshold 100 burst-threshold 100
Device(config-profile)# threat-detection rate inspect-drop average-time-frame 600 average-threshold 100 burst-threshold 100
Device(config-profile)# threat-detection rate syn-attack average-time-frame 600 average-threshold 100 burst-threshold 100
Device(config-profile)# exit
Device(config)# zone security public
Device(config-sec-zone)# protection zone-pmap1
Device(config-sec-zone)# exit
Device(config)# zone-pair security private2public source private destination public
Device(config-sec-zone-pair)# end

                    Example: Configuring the per-Box Half-Opened Session Limit

                    Device# configure terminal  
Device(config)# parameter-map type inspect global 
Device(config-profile)# alert on 
Device(config-profile)# per-box max-incomplete 12345   
Device(config-profile)# session total 34500  
Device(config-profile)# end

                    Example: Configuring the Half-Opened Session Limit for an Inspect VRF Parameter Map

                    Device# configure terminal  
Device(config)# parameter-map type inspect vrf vrf1-pmap 
Device(config-profile)# alert on 
Device(config-profile)# max-incomplete 3500 
Device(config-profile)# session total 34500 
Device(config-profile)# exit
Device(config)# parameter-map type inspect global
Device(config-profile)# alert on
Device(config-profile)# vrf vrf1 inspect vrf1-pmap 
Device(config-profile)# end

                    Example: Configuring the Global TCP SYN Flood Limit

                    Device# configure terminal  
Device(config)# parameter-map type inspect global 
Device(config-profile)# alert on 
Device(config-profile)# per-box tcp syn-flood limit 500 
Device(config-profile)# end

                    Additional References for Protection Against Distributed Denial of Service Attacks

                    Related Documents

                    Related Topic

                    Document Title

                    Cisco IOS commands

                    Cisco IOS Master Command List, All Releases

                    Security commands

                    Cisco IOS Security Command Reference

                    Firewall resource management

                    Configuring Firewall Resource Management feature

                    Firewall TCP SYN cookie

                    Configuring Firewall TCP SYN Cookie feature

                    Technical Assistance

                    Description

                    Link

                    The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

                    http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

                    Feature Information for Protection Against Distributed Denial of Service Attacks

                    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

                    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
                    Table 2 Feature Information for Protection Against Distributed Denial of Service Attacks

                    Feature Name

                    Releases

                    Feature Information

                    Protection Against Distributed Denial of Service Attacks

                    Cisco IOS XE Release 3.4S

                    The Protection Against Distributed Denial of Service Attacks feature provides protection from DoS attacks at the per-box level (for all firewall sessions) and at the VRF level. You can configure the aggressive aging of firewall sessions, event rate monitoring of firewall sessions, the half-opened connections limit, and global TCP SYN cookie protection to prevent DDoS attacks.

                    The following commands were introduced or modified: clear policy-firewall stats global, max-incomplete, max-incomplete aggressive-aging, per-box aggressive-aging, per-box max-incomplete, per-box max-incomplete aggressive-aging, per-box tcp syn-flood limit, session total, show policy-firewall stats global, show policy-firewall stats zone, threat-detection basic-threat, threat-detection rate, and udp half-open.