V-220453

Discussion

The OOBM access switch will connect to the management interface of the managed network elements. The management interface can be a true OOBM interface or a standard interface functioning as the management interface. In either case, the management interface of the managed network element will be directly connected to the OOBM network. An OOBM interface does not forward transit traffic, thereby providing complete separation of production and management traffic. Since all management traffic is immediately forwarded into the management network, it is not exposed to possible tampering. The separation also ensures that congestion or failures in the managed network do not affect the management of the device. If the device does not have an OOBM port, the interface functioning as the management interface must be configured so that management traffic does not leak into the managed network and production traffic does not leak into the management network.

Check Content

This requirement is only applicable where management access to the switch is via an OOBM interface, which is not a true OOBM interface. 

Step 1: Verify that the managed interface has an inbound and outbound access control list (ACL) configured. 

interface GigabitEthernet0/7 
 no switchport 
 description link to OOBM access switch 
 ip address 10.11.1.22 255.255.255.0 
 ip access-group INGRESS_MANAGEMENT_ACL in 
 ip access-group EGRESS_MANAGEMENT_ACL in 

Step 2: Verify that the ingress ACL only allows management and ICMP traffic. 

ip access-list extended INGRESS_MANAGEMENT_ACL 
 permit tcp any host 10.11.1.22 eq tacacs 
 permit tcp any host 10.11.1.22 eq 22 
 permit udp any host 10.11.1.22 eq snmp 
 permit udp any host 10.11.1.22 eq snmptrap 
 permit udp any host 10.11.1.22 eq ntp 
 permit icmp any host 10.11.1.22 
 deny ip any any log-input 

Step 3: Verify that the egress ACL blocks any transit traffic. 

ip access-list extended EGRESS_MANAGEMENT_ACL 
 deny ip any any log-input 

Note: On Cisco switches, local generated packets are not inspected by outgoing interface access lists. Hence, the above configuration would drop any packets not generated by the switch, blocking any transit traffic. 

If the switch does not restrict traffic that ingresses and egresses the management interface, this is a finding.