Detections
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CISC-RT-000130 - The Cisco router must be configured to restrict traffic destined to itself.

Information

The route processor handles traffic destined to the router-the key component used to build forwarding paths and is instrumental with all network management functions. Hence, any disruption or DoS attack to the route processor can result in mission critical network outages.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

Configure the ACL for any external interfaces as shown in the example.

RP/0/0/CPU0:R3(config)#ipv4 access-list EXTERNAL_ACL_INBOUND
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp host x.11.1.1 eq bgp host x.11.1.2
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp host x.11.1.1 host x.11.1.2 eq bgp
RP/0/0/CPU0:R3(config-ipv4-acl)#permit icmp host x.11.1.1 host x.11.1.2 echo
RP/0/0/CPU0:R3(config-ipv4-acl)#permit icmp host x.11.1.1 host x.11.1.2 echo-reply
RP/0/0/CPU0:R3(config-ipv4-acl)#deny ip any host x.11.1.1 log
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp any any established
...
...
...
RP/0/0/CPU0:R3(config-ipv4-acl)#deny ip any any log
RP/0/0/CPU0:R3(config-ipv4-acl)#exit

Configure the ACL for any external interfaces as shown in the example.

RP/0/0/CPU0:R3(config)#ipv4 access-list INTERNAL_ACL_INBOUND
RP/0/0/CPU0:R3(config-ipv4-acl)#permit icmp any any
RP/0/0/CPU0:R3(config-ipv4-acl)#permit ospf host 10.1.12.1 host 10.1.12.2
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2eq 22
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2eq tacacs
RP/0/0/CPU0:R3(config-ipv4-acl)#permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq snmp
RP/0/0/CPU0:R3(config-ipv4-acl)#permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq ntp
RP/0/0/CPU0:R3(config-ipv4-acl)#deny ip any host 10.1.12.2 log
RP/0/0/CPU0:R3(config-ipv4-acl)#permit ip any any
RP/0/0/CPU0:R3(config-ipv4-acl)#exit

Note: best practice is to configure the ACL statements relative to traffic destined to the router first followed by ACL statements for transit traffic.

Step 2: Apply the ACLs to the appropriate interface as shown in the example below.

RP/0/0/CPU0:R3(config)#int g0/0/0/1
RP/0/0/CPU0:R3(config-if)#ipv4 access-group EXTERNAL_ACL_INBOUND in
RP/0/0/CPU0:R3(config-if)#exit
RP/0/0/CPU0:R3(config)#int g0/0/0/2
RP/0/0/CPU0:R3(config-if)#ipv4 access-group INTERNAL_ACL_INBOUND in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XR_Router_Y23M10_STIG.zip

Item Details

References: CAT|I, CCI|CCI-001097, Rule-ID|SV-216743r531087_rule, STIG-ID|CISC-RT-000130, STIG-Legacy|SV-105831, STIG-Legacy|V-96693, Vuln-ID|V-216743

Plugin: Cisco

Control ID: c908c354c6520fc79df57ab07158021ecf686dd77017f55274ff303780ea5552