STIGQter: STIG Summary: Cisco NX-OS Switch NDM Security Technical Implementation Guide Version: 2 Release: 2 Benchmark Date: 23 Apr 2021:

The Cisco switch must be configured to protect against known types of denial-of-service (DoS) attacks by employing organization-defined security safeguards.

DISA Rule

SV-220505r604141_rule

Vulnerability Number

V-220505

Group Title

SRG-APP-000435-NDM-000315

Rule Version

CISC-ND-001220

Severity

CAT II

CCI(s)

• CCI-002385 - The information system protects against or limits the effects of organization-defined types of denial of service attacks by employing organization-defined security safeguards.

Weight

10

Fix Recommendation

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

Check Contents

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 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
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 switch
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

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.

Vulnerability Number

V-220505

Documentable

False

Rule Version

CISC-ND-001220

Severity Override Guidance

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 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
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 switch
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

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.

Check Content Reference

M

Target Key

4066

Comments