The Cisco switch must be configured to enforce a Quality-of-Service (QoS) policy to limit the effects of packet flooding denial-of-service (DoS) attacks.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-221131	CISC-RT-000780	SV-221131r622190_rule		Medium

Description
DoS is a condition when a resource is not available for legitimate users. Packet flooding distributed denial-of-service (DDoS) attacks are referred to as volumetric attacks and have the objective of overloading a network or circuit to deny or seriously degrade performance, which denies access to the services that normally traverse the network or circuit. Volumetric attacks have become relatively easy to launch using readily available tools such as Low Orbit Ion Cannon or botnets. Measures to mitigate the effects of a successful volumetric attack must be taken to ensure that sufficient capacity is available for mission-critical traffic. Managing capacity may include, for example, establishing selected network usage priorities or quotas and enforcing them using rate limiting, Quality of Service (QoS), or other resource reservation control methods. These measures may also mitigate the effects of sudden decreases in network capacity that are the result of accidental or intentional physical damage to telecommunications facilities (such as cable cuts or weather-related outages).

Description

DoS is a condition when a resource is not available for legitimate users. Packet flooding distributed denial-of-service (DDoS) attacks are referred to as volumetric attacks and have the objective of overloading a network or circuit to deny or seriously degrade performance, which denies access to the services that normally traverse the network or circuit. Volumetric attacks have become relatively easy to launch using readily available tools such as Low Orbit Ion Cannon or botnets. Measures to mitigate the effects of a successful volumetric attack must be taken to ensure that sufficient capacity is available for mission-critical traffic. Managing capacity may include, for example, establishing selected network usage priorities or quotas and enforcing them using rate limiting, Quality of Service (QoS), or other resource reservation control methods. These measures may also mitigate the effects of sudden decreases in network capacity that are the result of accidental or intentional physical damage to telecommunications facilities (such as cable cuts or weather-related outages).

STIG	Date
Cisco NX OS Switch RTR Security Technical Implementation Guide	2023-02-15

Details

Check Text ( C-22846r409882_chk )
Step 1: Verify that a class map has been configured for the Scavenger class as shown in the example below: class-map match-all SCAVENGER match ip dscp cs1 Step 2: Verify that the policy map includes the SCAVENGER class with low priority as shown in the following example below: policy-map QOS_POLICY class CONTROL_PLANE priority percent 10 class C2_VOICE priority percent 10 class VOICE priority percent 15 class VIDEO bandwidth percent 25 class PREFERRED_DATA bandwidth percent 25 class SCAVENGER bandwidth percent 5 class class-default bandwidth percent 10 Note: Traffic out of profile must be marked at the customer access layer or CE egress edge. If the switch is not configured to enforce a QoS policy to limit the effects of packet flooding DoS attacks, this is a finding.

Check Text ( C-22846r409882_chk )

Step 1: Verify that a class map has been configured for the Scavenger class as shown in the example below:

class-map match-all SCAVENGER
match ip dscp cs1

Step 2: Verify that the policy map includes the SCAVENGER class with low priority as shown in the following example below:

policy-map QOS_POLICY
class CONTROL_PLANE
priority percent 10
class C2_VOICE
priority percent 10
class VOICE
priority percent 15
class VIDEO
bandwidth percent 25
class PREFERRED_DATA
bandwidth percent 25
class SCAVENGER
bandwidth percent 5
class class-default
bandwidth percent 10

Note: Traffic out of profile must be marked at the customer access layer or CE egress edge.

If the switch is not configured to enforce a QoS policy to limit the effects of packet flooding DoS attacks, this is a finding.

Fix Text (F-22835r409883_fix)
Step 1: Configure a class map for the SCAVENGER class. SW1(config)# class-map match-all SCAVENGER SW1(config-cmap)# match ip dscp cs1 Step 2: Add the SCAVENGER class to the policy map as shown in the example below: SW1(config)# policy-map QOS_POLICY SW1(config-pmap-c)# no class class-default SW1(config-pmap)# class SCAVENGER SW1(config-pmap-c)# bandwidth percent 5 SW1(config-pmap-c)# class class-default SW1(config-pmap-c)# bandwidth percent 10 SW1(config-pmap-c)# end

Fix Text (F-22835r409883_fix)

Step 1: Configure a class map for the SCAVENGER class.

SW1(config)# class-map match-all SCAVENGER
SW1(config-cmap)# match ip dscp cs1

Step 2: Add the SCAVENGER class to the policy map as shown in the example below:

SW1(config)# policy-map QOS_POLICY
SW1(config-pmap-c)# no class class-default
SW1(config-pmap)# class SCAVENGER
SW1(config-pmap-c)# bandwidth percent 5
SW1(config-pmap-c)# class class-default
SW1(config-pmap-c)# bandwidth percent 10
SW1(config-pmap-c)# end