The Cisco IOS XE router must manage excess bandwidth to limit the effects of packet flooding types of denial of service (DoS) attacks.

From Cisco IOS XE Release 3 RTR Security Technical Implementation Guide

Part of SRG-NET-000193-RTR-000111

Associated with: CCI-001095

SV-88805r2_rule The Cisco IOS XE router must manage excess bandwidth to limit the effects of packet flooding types of denial of service (DoS) attacks.

Vulnerability discussion

Denial of service is a condition when a resource is not available for legitimate users. Packet flooding 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 by 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).

Check content

Review the Cisco IOS XE router configuration. Interview the system administrator to verify that Quality of Service (QoS) has been implemented to ensure capacity is available for mission-critical, voice, and control plane traffic during periods of congestion. The following steps should be used to verify the configuration. Step 1: Verify that the class-maps are configured to match on DSCP values that have been set at the edges as shown in the configuration example below: class-map match-all CONTROL_PLANE match ip dscp 48 class-map match-all C2_VOICE match ip dscp 47 class-map match-all VOICE match ip dscp ef class-map match-all VIDEO match ip dscp af4 class-map match-all CRITICAL_DATA match ip dscp af3 Step 2: Verify that the policy map applied to the core-layer-facing interface reserves the bandwidth for each traffic type as shown in the following example: 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 CRITICAL_DATA bandwidth percent 25 class class-default bandwidth percent 15 Step 3: Verify that an output service policy is bound to the core-layer-facing interface as shown in the configuration example below: interface GigabitEthernet1/1 ip address x.x.x.x 255.255.255.0 service-policy output QOS_POLICY If QoS policy has not been implemented to ensure there is capacity available for critical, voice, and control plane traffic during periods of congestion, this is a finding.

Fix text

Configure a QOS policy on the Cisco IOS XE router to ensure capacity is available for mission-critical, voice, and control plane traffic during periods of congestion. The configuration should look similar to the following: class-map match-all CONTROL_PLANE match ip dscp 48 class-map match-all C2_VOICE match ip dscp 47 class-map match-all VOICE match ip dscp ef class-map match-all VIDEO match ip dscp af4 class-map match-all CRITICAL_DATA match ip dscp af3 … … … 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 CRITICAL_DATA bandwidth percent 25 class class-default bandwidth percent 15 … … … interface GigabitEthernet1/1 ip address x.x.x.x 255.255.255.0 service-policy output QOS_POLICY

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