Title

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

Discussion

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 in 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 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. 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.

Check Content

Review the configuration to verify Cisco ACI is configured to employ control plane protection. 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: (config)# leaf 101 (config-leaf)# int eth 1/10 (config-leaf-if)# service-policy type control-plane-if 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

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 the ACL's specific traffic types. Apic1(config)#ip access-list extended CoPP_CRITICAL Apic1(config-ext-nacl)#remark our control plane adjacencies are critical Apic1(config-ext-nacl)#permit ospf host x.x.x.x any Apic1(config-ext-nacl)#permit ospf host x.x.x.x any Apic1(config-ext-nacl)#permit pim host x.x.x.x any Apic1(config-ext-nacl)#permit pim host x.x.x.x any Apic1(config-ext-nacl)#permit igmp any 224.0.0.0 15.255.255.255 Apic1(config-ext-nacl)#permit tcp host x.x.x.x eq bgp host x.x.x.x Apic1(config-ext-nacl)#deny ip any any Apic1(config-ext-nacl)#exit Apic1(config)#ip access-list extended CoPP_IMPORTANT Apic1(config-ext-nacl)#permit tcp host x.x.x.x eq tacacs any Apic1(config-ext-nacl)#permit tcp x.x.x.x 0.0.0.255 any eq 22 Apic1(config-ext-nacl)#permit udp host x.x.x.x any eq snmp Apic1(config-ext-nacl)#permit udp host x.x.x.x eq ntp any Apic1(config-ext-nacl)#deny ip any any Apic1(config-ext-nacl)#exit Apic1(config)#ip access-list extended CoPP_NORMAL Apic1(config-ext-nacl)#remark we will want to rate limit ICMP traffic Apic1(config-ext-nacl)#deny icmp any host x.x.x.x fragments Apic1(config-ext-nacl)#permit icmp any any echo Apic1(config-ext-nacl)#permit icmp any any echo-reply Apic1(config-ext-nacl)#permit icmp any any time-exceeded Apic1(config-ext-nacl)#permit icmp any any unreachable Apic1(config-ext-nacl)#deny ip any any Apic1(config-ext-nacl)#exit Apic1(config)#ip access-list extended CoPP_UNDESIRABLE Apic1(config-ext-nacl)#remark management plane traffic that should not be received Apic1(config-ext-nacl)#permit udp any any eq ntp Apic1(config-ext-nacl)#permit udp any any eq snmp Apic1(config-ext-nacl)#permit tcp any any eq 22 Apic1(config-ext-nacl)#permit tcp any any eq 23 Apic1(config-ext-nacl)#remark control plane traffic not configured on router Apic1(config-ext-nacl)#permit eigrp any any Apic1(config-ext-nacl)#permit udp any any eq rip Apic1(config-ext-nacl)#deny ip any any Apic1(config-ext-nacl)#exit Apic1(config)#ip access-list extended CoPP_DEFAULT Apic1(config-ext-nacl)#permit ip any any Apic1(config-ext-nacl)#exit Step 2: Configure class maps referencing each of the ACLs. Apic1(config)#class-map match-all CoPP_CRITICAL Apic1(config-cmap)#match access-group name CoPP_CRITICAL Apic1(config-cmap)#class-map match-any CoPP_IMPORTANT Apic1(config-cmap)#match access-group name CoPP_IMPORTANT Apic1(config-cmap)#match protocol arp Apic1(config-cmap)#class-map match-all CoPP_NORMAL Apic1(config-cmap)#match access-group name CoPP_NORMAL Apic1(config-cmap)#class-map match-any CoPP_UNDESIRABLE Apic1(config-cmap)#match access-group name CoPP_UNDESIRABLE Apic1(config-cmap)#class-map match-all CoPP_DEFAULT Apic1(config-cmap)#match access-group name CoPP_DEFAULT Apic1(config-cmap)#exit Step 3: Configure a policy map referencing the configured class maps and apply appropriate bandwidth allowance and policing attributes. Apic1(config)#policy-map CONTROL_PLANE_POLICY Apic1(config-pmap)#class CoPP_CRITICAL Apic1(config-pmap-c)#police 512000 8000 conform-action transmit exceed-action transmit Apic1(config-pmap-c-police)#class CoPP_IMPORTANT Apic1(config-pmap-c)#police 256000 4000 conform-action transmit exceed-action drop Apic1(config-pmap-c-police)#class CoPP_NORMAL Apic1(config-pmap-c)#police 128000 2000 conform-action transmit exceed-action drop Apic1(config-pmap-c-police)#class CoPP_UNDESIRABLE Apic1(config-pmap-c)#police 8000 1000 conform-action drop exceed-action drop Apic1(config-pmap-c-police)#class CoPP_DEFAULT Apic1(config-pmap-c)#police 64000 1000 conform-action transmit exceed-action drop Apic1(config-pmap-c-police)#exit apic(config-pmap-c)#exit apic(config-pmap)#exit Step 4: Apply the policy map applying the configuration to an interface on the leaf. apic(config)# leaf 101 (config-leaf)# int eth 1/10 (config-leaf-if)# service-policy type CONTROL-PLANE-POLICY

Additional Identifiers

Rule ID: SV-272104r1064507_rule

Vulnerability ID: V-272104

Group Title: SRG-NET-000362-RTR-000110

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.