The Cisco router must be configured to protect against or limit the effects of denial of service (DoS) attacks by employing control plane protection.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-216650	CISC-RT-000120	SV-216650r929055_rule		High

Description

The Route Processor (RP) is critical to all network operations because it is the component used to build all forwarding paths for the data plane via control plane processes. It is also instrumental with ongoing network management functions that keep the routers and links available for providing network services. Any disruption to the RP or the control and management planes can result in mission-critical network outages. A DoS attack targeting the RP can result in excessive CPU and memory utilization. To maintain network stability and RP security, the router must be able to handle specific control plane and management plane traffic that is destined to the RP. In the past, one method of filtering was to use ingress filters on forwarding interfaces to filter both forwarding path and receiving path traffic, as well as limiting traffic destined to the device. However, this method does not scale well as the number of interfaces grows and the size of the ingress filters grows. Control plane policing increases the security of routers and multilayer switches by protecting the RP from unnecessary or malicious traffic. Filtering and rate limiting the traffic flow of control plane packets can be implemented to protect routers against reconnaissance and DoS attacks, allowing the control plane to maintain packet forwarding and protocol states despite an attack or heavy load on the router or multilayer switch.

STIG	Date
Cisco IOS XE Router RTR Security Technical Implementation Guide	2023-09-13

Details

Check Text ( C-17883r929053_chk )

Review the Cisco router configuration to verify it is compliant with this requirement. Step 1: Verify traffic types have been classified based on importance levels. The following is an example configuration: class-map match-all CoPP_CRITICAL match access-group name CoPP_CRITICAL class-map match-any CoPP_IMPORTANT match access-group name CoPP_IMPORTANT match protocol arp class-map match-all CoPP_NORMAL match access-group name CoPP_NORMAL class-map match-any CoPP_UNDESIRABLE match access-group name CoPP_UNDESIRABLE class-map match-all CoPP_DEFAULT match access-group name CoPP_DEFAULT Step 2: Review the Access Control Lists(ACLs) referenced by the class maps to determine if the traffic is being classified appropriately. The following is an example configuration: ip access-list extended CoPP_CRITICAL remark our control plane adjacencies are critical permit ospf host [OSPF neighbor A] any permit ospf host [OSPF neighbor B] any permit pim host [PIM neighbor A] any permit pim host [PIM neighbor B] any permit pim host [RP addr] any permit igmp any 224.0.0.0 15.255.255.255 permit tcp host [BGP neighbor] eq bgp host [local BGP addr] permit tcp host [BGP neighbor] host [local BGP addr] eq bgp deny ip any any ip access-list extended CoPP_IMPORTANT permit tcp host [TACACS server] eq tacacs any permit tcp [management subnet] 0.0.0.255 any eq 22 permit udp host [SNMP manager] any eq snmp permit udp host [NTP server] eq ntp any deny ip any any ip access-list extended CoPP_NORMAL remark we will want to rate limit ICMP traffic deny icmp any host x.x.x.x fragments permit icmp any any echo permit icmp any any echo-reply permit icmp any any time-exceeded permit icmp any any unreachable deny ip any any ip access-list extended CoPP_UNDESIRABLE remark other management plane traffic that should not be received permit udp any any eq ntp permit udp any any eq snmp permit tcp any any eq 22 permit tcp any any eq 23 remark other control plane traffic not configured on router permit eigrp any any permit udp any any eq rip deny ip any any ip access-list extended CoPP_DEFAULT permit ip any any Note: Explicitly defining undesirable traffic with ACL entries enables the network operator to collect statistics. Excessive ARP packets can potentially monopolize Route Processor resources, starving other important processes. Currently, ARP is the only Layer 2 protocol that can be specifically classified using the match protocol command. Step 3: Review the policy-map to determine if the traffic is being policed appropriately for each classification. The following is an example configuration: policy-map CONTROL_PLANE_POLICY class CoPP_CRITICAL police 512000 8000 conform-action transmit exceed-action transmit class CoPP_IMPORTANT police 256000 4000 conform-action transmit exceed-action drop class CoPP_NORMAL police 128000 2000 conform-action transmit exceed-action drop class CoPP_UNDESIRABLE police 8000 1000 conform-action drop exceed-action drop class CoPP_DEFAULT police 64000 1000 conform-action transmit exceed-action drop Step 4: Verify that the CoPP policy is enabled. The following is an example configuration: control-plane service-policy input CONTROL_PLANE_POLICY Note: Control Plane Protection (CPPr) can be used to filter as well as police control plane traffic destined to the RP. CPPr is very similar to CoPP and has the ability to filter and police traffic using finer granularity by dividing the aggregate control plane into three separate categories: (1) host, (2) transit, and (3) CEF-exception. Hence, a separate policy-map could be configured for each traffic category. If the Cisco router is not configured to protect against known types of DoS attacks by employing organization-defined security safeguards, this is a finding.

Fix Text (F-17881r929054_fix)

Configure the Cisco router to protect against known types of DoS attacks on the route processor. Implementing a CoPP policy as shown in the example below is a best practice method. Step 1: Configure ACLs specific traffic types. R1(config)#ip access-list extended CoPP_CRITICAL R1(config-ext-nacl)#remark our control plane adjacencies are critical R1(config-ext-nacl)#permit ospf host x.x.x.x any R1(config-ext-nacl)#permit ospf host x.x.x.x any R1(config-ext-nacl)#permit pim host x.x.x.x any R1(config-ext-nacl)#permit pim host x.x.x.x any R1(config-ext-nacl)#permit igmp any 224.0.0.0 15.255.255.255 R1(config-ext-nacl)#permit tcp host x.x.x.x eq bgp host x.x.x.x R1(config-ext-nacl)#deny ip any any R1(config-ext-nacl)#exit R1(config)#ip access-list extended CoPP_IMPORTANT R1(config-ext-nacl)#permit tcp host x.x.x.x eq tacacs any R1(config-ext-nacl)#permit tcp x.x.x.x 0.0.0.255 any eq 22 R1(config-ext-nacl)#permit udp host x.x.x.x any eq snmp R1(config-ext-nacl)#permit udp host x.x.x.x eq ntp any R1(config-ext-nacl)#deny ip any any R1(config-ext-nacl)#exit R1(config)#ip access-list extended CoPP_NORMAL R1(config-ext-nacl)#remark we will want to rate limit ICMP traffic R1(config-ext-nacl)#deny icmp any host x.x.x.x fragments R1(config-ext-nacl)#permit icmp any any echo R1(config-ext-nacl)#permit icmp any any echo-reply R1(config-ext-nacl)#permit icmp any any time-exceeded R1(config-ext-nacl)#permit icmp any any unreachable R1(config-ext-nacl)#deny ip any any R1(config-ext-nacl)#exit R1(config)#ip access-list extended CoPP_UNDESIRABLE R1(config-ext-nacl)#remark management plane traffic that should not be received R1(config-ext-nacl)#permit udp any any eq ntp R1(config-ext-nacl)#permit udp any any eq snmp R1(config-ext-nacl)#permit tcp any any eq 22 R1(config-ext-nacl)#permit tcp any any eq 23 R1(config-ext-nacl)#remark control plane traffic not configured on router R1(config-ext-nacl)#permit eigrp any any R1(config-ext-nacl)#permit udp any any eq rip R1(config-ext-nacl)#deny ip any any R1(config-ext-nacl)#exit R1(config)#ip access-list extended CoPP_DEFAULT R1(config-ext-nacl)#permit ip any any R1(config-ext-nacl)#exit Step 2: Configure class maps referencing each of the ACLs. R1(config)#class-map match-all CoPP_CRITICAL R1(config-cmap)#match access-group name CoPP_CRITICAL R1(config-cmap)#class-map match-any CoPP_IMPORTANT R1(config-cmap)#match access-group name CoPP_IMPORTANT R1(config-cmap)#match protocol arp R1(config-cmap)#class-map match-all CoPP_NORMAL R1(config-cmap)#match access-group name CoPP_NORMAL R1(config-cmap)#class-map match-any CoPP_UNDESIRABLE R1(config-cmap)#match access-group name CoPP_UNDESIRABLE R1(config-cmap)#class-map match-all CoPP_DEFAULT R1(config-cmap)#match access-group name CoPP_DEFAULT R1(config-cmap)#exit Step 3: Configure a policy map referencing the configured class maps and apply appropriate bandwidth allowance and policing attributes. R1(config)#policy-map CONTROL_PLANE_POLICY R1(config-pmap)#class CoPP_CRITICAL R1(config-pmap-c)#police 512000 8000 conform-action transmit exceed-action transmit R1(config-pmap-c-police)#class CoPP_IMPORTANT R1(config-pmap-c)#police 256000 4000 conform-action transmit exceed-action drop R1(config-pmap-c-police)#class CoPP_NORMAL R1(config-pmap-c)#police 128000 2000 conform-action transmit exceed-action drop R1(config-pmap-c-police)#class CoPP_UNDESIRABLE R1(config-pmap-c)#police 8000 1000 conform-action drop exceed-action drop R1(config-pmap-c-police)#class CoPP_DEFAULT R1(config-pmap-c)#police 64000 1000 conform-action transmit exceed-action drop R1(config-pmap-c-police)#exit R1(config-pmap-c)#exit R1(config-pmap)#exit Step 4: Apply the policy map to the control plane. R1(config)#control-plane R1(config-cp)#service-policy input CONTROL_PLANE_POLICY R1(config-cp)#end