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The Cisco switch must be configured to restrict traffic destined to itself.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-221080 | CISC-RT-000130 | SV-221080r622190_rule | High |
| Description |
|---|
| The route processor handles traffic destined to the switch—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. |
| STIG | Date |
|---|---|
| Cisco NX-OS Switch RTR Security Technical Implementation Guide | 2021-03-29 |
Details
| Check Text ( C-22795r409729_chk ) |
|---|
| Review the external and internal ACLs to verify that the switch 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 ICMP, all other traffic destined to the switch should be dropped. ip access-list EXTERNAL_ACL 10 permit tcp x.11.1.1/32 eq bgp x.11.1.2/32 20 permit tcp x.11.1.1/32 x.11.1.2/32 eq bgp 30 permit icmp x.11.1.1/32 x.11.1.2/32 echo 40 permit icmp x.11.1.1/32 x.11.1.2/32 echo-reply 50 deny ip any x.11.1.1/32 log 60 permit … … … … 90 deny ip any any log ip access-list INTERNAL_ACL 10 permit icmp any any 20 permit ospf 10.1.12.1/32 10.1.12.2/32 30 permit tcp 10.2.1.0/24 10.1.12.2/32 eq 22 40 permit tcp 10.2.1.0/24 10.1.12.2/32 eq tacacs 50 permit udp 10.2.1.0/24 10.1.12.2/32 eq snmp 60 permit udp 10.2.1.0/24 10.1.12.2/32 eq ntp 70 deny ip any 10.1.12.2/32 log 80 permit …. 90 deny ip any any log Note: For the internal ACL example, all switches 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 switch 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 Ethernet1/2 no switchport ip access-group EXTERNAL_ACL in ip address x.11.1.2 255.255.255.254 interface Ethernet1/3 no switchport ip access-group INTERNAL_ACL in ip address 10.1.12.2 255.255.255.0 If the switch is not configured to restrict traffic destined to itself, this is a finding. |
| Fix Text (F-22784r409730_fix) |
|---|
| Step 1: Configure the ACL for any external interfaces as shown in the example below: SW1(config)# ip access-list EXTERNAL_ACL SW1(config-acl)# permit tcp host x.11.1.1 eq bgp host x.11.1.2 SW1(config-acl)# permit tcp host x.11.1.1 host x.11.1.2 eq bgp SW1(config-acl)# permit icmp host x.11.1.1 host x.11.1.2 echo SW1(config-acl)# permit icmp host x.11.1.1 host x.11.1.2 echo-reply SW1(config-acl)# deny ip any host x.11.1.1 log SW1(config-acl)# permit … … … … SW1(config-acl)# deny ip any any log Configure the ACL for any external interfaces as shown in the example below: SW1(config)# ip access-list INTERNAL_ACL SW1(config-acl)# permit ospf host 10.1.12.1 host 10.1.12.2 SW1(config-acl)# permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq 22 SW1(config-acl)# permit tcp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq tacacs SW1(config-acl)# permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq snmp SW1(config-acl)# permit udp 10.2.1.0 0.0.0.255 host 10.1.12.2 eq ntp SW1(config-acl)# deny ip any host 10.1.12.2 log SW1(config-acl)# permit … … … … SW1(config-acl)# permit ip any any log SW1(config-acl)# exit Note: best practice is to configure the ACL statements relative to traffic destined to the switch first followed by ACL statements for transit traffic. Step 2: Apply the ACLs to the appropriate interface as shown in the example below: SW1(config)# int e1/2 SW1(config-if)# ip access-group EXTERNAL_ACL in SW1(config)# int e1/3 SW1(config-if)# ip access-group INTERNAL_ACL in |