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The Cisco switch 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-221079 | CISC-RT-000120 | SV-221079r622190_rule | Medium |
| 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 switches 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 switch 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. 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 switches 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 switches against reconnaissance and DoS attacks, allowing the control plane to maintain packet forwarding and protocol states despite an attack or heavy load on the switch or multilayer switch. |
| STIG | Date |
|---|---|
| Cisco NX-OS Switch RTR Security Technical Implementation Guide | 2021-03-29 |
Details
| Check Text ( C-22794r409726_chk ) |
|---|
| Review the Cisco switch configuration to verify that 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 ACLs referenced by the class maps to determine if the traffic is being classified appropriately. The following is an example configuration: ip access-list 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 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 CoPP_NORMAL remark we will want to rate limit ICMP traffic 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 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 switch permit eigrp any any permit udp any any eq rip deny ip any any ip access-list 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 If the Cisco switch is not configured to protect against known types of DoS attacks by employing organization-defined security safeguards, this is a finding. |
| Fix Text (F-22783r409727_fix) |
|---|
| Configure the Cisco switch 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. SW1(config)# ip access-list CoPP_CRITICAL SW1(config-acl)# remark our control plane adjacencies are critical SW1(config-acl)# permit ospf host 10.1.12.1 any SW1(config-acl)# permit ospf host 10.1.22.1 any SW1(config-acl)# permit pim host 10.1.12.1 any SW1(config-acl)# permit pim host 10.1.22.1 any SW1(config-acl)# permit pim host 10.1.33.4 any SW1(config-acl)# permit igmp any 224.0.0.0 15.255.255.255 SW1(config-acl)# permit tcp host 10.2.33.3 eq bgp host 10.2.33.4 SW1(config-acl)# permit tcp host 10.2.33.3 host 10.2.33.4 eq bgp SW1(config-acl)# deny ip any any SW1(config-acl)# exit SW1(config)# ip access-list CoPP_IMPORTANT SW1(config-acl)# permit tcp host 10.1.33.5 eq tacacs any SW1(config-acl)# permit tcp 10.1.33.0 0.0.0.255 any eq 22 SW1(config-acl)# permit udp host 10.1.33.7 any eq snmp SW1(config-acl)# permit udp host 10.1.33.9 eq ntp any SW1(config-acl)# deny ip any any SW1(config-acl)# exit SW1(config)# ip access-list CoPP_NORMAL SW1(config-acl)# remark we will want to rate limit ICMP traffic SW1(config-acl)# permit icmp any any echo SW1(config-acl)# permit icmp any any echo-reply SW1(config-acl)# permit icmp any any time-exceeded SW1(config-acl)# permit icmp any any unreachable SW1(config-acl)# deny ip any any SW1(config-acl)# exit SW1(config)# ip access-list CoPP_UNDESIRABLE SW1(config-acl)# remark other management plane traffic that should not be received SW1(config-acl)# permit udp any any eq ntp SW1(config-acl)# permit udp any any eq snmp SW1(config-acl)# permit tcp any any eq 22 SW1(config-acl)# permit tcp any any eq 23 SW1(config-acl)# remark other control plane traffic not configured on switch SW1(config-acl)# permit eigrp any any SW1(config-acl)# permit udp any any eq rip SW1(config-acl)# deny ip any any SW1(config-acl)# exit SW1(config)# ip access-list CoPP_DEFAULT SW1(config-acl)# permit ip any any SW1(config-acl)# exit Step 2: Configure class maps referencing each of the ACLs. SW1(config)# class-map match-all CoPP_CRITICAL SW1(config-cmap)# match access-group name CoPP_CRITICAL SW1(config-cmap)# class-map match-any CoPP_IMPORTANT SW1(config-cmap)# match access-group name CoPP_IMPORTANT SW1(config-cmap)# match protocol arp SW1(config-cmap)# class-map match-all CoPP_NORMAL SW1(config-cmap)# match access-group name CoPP_NORMAL SW1(config-cmap)# class-map match-any CoPP_UNDESIRABLE SW1(config-cmap)# match access-group name CoPP_UNDESIRABLE SW1(config-cmap)# class-map match-all CoPP_DEFAULT SW1(config-cmap)# match access-group name CoPP_DEFAULT SW1(config-cmap)# exit Step 3: Configure a policy map referencing the configured class maps and apply appropriate bandwidth allowance and policing attributes. SW1(config)# policy-map CONTROL_PLANE_POLICY SW1(config-pmap)# class CoPP_CRITICAL SW1(config-pmap-c)# police 512000 8000 conform-action transmit exceed-action transmit SW1(config-pmap-c-police)# class CoPP_IMPORTANT SW1(config-pmap-c)# police 256000 4000 conform-action transmit exceed-action drop SW1(config-pmap-c-police)# class CoPP_NORMAL SW1(config-pmap-c)# police 128000 2000 conform-action transmit exceed-action drop SW1(config-pmap-c-police)# class CoPP_UNDESIRABLE SW1(config-pmap-c)# police 8000 1000 conform-action drop exceed-action drop SW1(config-pmap-c-police)# class CoPP_DEFAULT SW1(config-pmap-c)# police 64000 1000 conform-action transmit exceed-action drop SW1(config-pmap-c-police)# exit SW1(config-pmap-c)# exit SW1(config-pmap)# exit Step 4: Apply the policy map to the control plane. SW1(config)# control-plane SW1(config-cp)# service-policy input CONTROL_PLANE_POLICY SW1(config-cp)# end |