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The Cisco router must be configured to restrict traffic destined to itself.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-216651 | CISC-RT-000130 | SV-216651r531086_rule | High |
| Description |
|---|
| 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 denial of service (DoS) attack to the route processor can result in mission critical network outages. |
| STIG | Date |
|---|---|
| Cisco IOS XE Router RTR Security Technical Implementation Guide | 2021-09-16 |
Details
| Check Text ( C-17884r287910_chk ) |
|---|
| Review the external and internal ACLs to verify that the router is configured to only allow specific management and control plane traffic from specific sources destined to itself. Step 1: Verify ACLs has been configured as shown in the example below that matches expected control plane and management plane traffic. With the exception of Internet Control Message Protocol (ICMP), all other traffic destined to the router should be dropped. ip access-list extended EXTERNAL_ACL permit tcp host x.11.1.1 eq bgp host x.11.1.2 permit tcp host x.11.1.1 host x.11.1.2 eq bgp permit icmp host x.11.1.1 host x.11.1.2 echo permit icmp host x.11.1.1 host x.11.1.2 echo-reply deny ip any host x.11.1.1 log-input permit … … … … deny ip any any log-input ip access-list extended INTERNAL_ACL permit icmp any any permit ospf host 10.1.12.1 host 10.1.12.2 permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq 22 permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq tacacs permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq snmp permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq ntp deny ip any host 10.1.12.2 log-input permit … … … … deny ip any any log-input Note: For the internal ACL example, all routers within the hypothetical network (10.1.0.0/16) have been configured to use the loopback address to source all management traffic (not shown); hence, the loopbacks are the only allowable destination address for management traffic. In addition, all management traffic destined to the router must originate from the management network (10.2.1.0/24). With the exception of link-local control plane traffic and ICMP, all other traffic destined to any physical interface address will be dropped. Step 2: Verify that the ACL has been applied to the appropriate interface as shown in the example below: interface GigabitEthernet0/2 ip address x.11.1.2 255.255.255.254 ip access-group EXTERNAL_ACL in interface GigabitEthernet0/3 ip address 10.1.12.2 255.255.255.0 ip access-group INTERNAL_ACL in If the router is not configured to restrict traffic destined to itself, this is a finding. |
| Fix Text (F-17882r287911_fix) |
|---|
| Step 1: Configure the ACL for any external interfaces as shown in the example. R1(config)#ip access-list extended EXTERNAL_ACL R1(config-ext-nacl)#permit tcp host x.11.1.1 eq bgp host x.11.1.2 R1(config-ext-nacl)#permit tcp host x.11.1.1 host x.11.1.2 eq bgp R1(config-ext-nacl)#permit icmp host x.11.1.1 host x.11.1.2 echo R1(config-ext-nacl)#permit icmp host x.11.1.1 host x.11.1.2 echo-reply R1(config-ext-nacl)#deny ip any host x.11.1.1 log-input R1(config-ext-nacl)#permit … … … … R1(config-ext-nacl)#deny ip any any log-input Step 2: Configure the ACL for any external interfaces as shown in the example. R1(config)#ip access-list extended INTERNAL_ACL R1(config-ext-nacl)#permit ospf host 10.1.12.1 host 10.1.12.2 R1(config-ext-nacl)#permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq 22 R1(config-ext-nacl)#permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq tacacs R1(config-ext-nacl)#permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq snmp R1(config-ext-nacl)#permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq ntp R1(config-ext-nacl)#deny ip any host 10.1.12.2 log-input R1(config-ext-nacl)#permit … … … … R1(config-ext-nacl)#permit ip any any log-input R1(config-ext-nacl)#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 3: Apply the ACLs to the appropriate interface as shown in the example below: R1(config)#int g0/2 R1(config-if)#ip access-group EXTERNAL_ACL in R1(config)#int g0/3 R1(config-if)#ip access-group INTERNAL_ACL in |