STIGQter: STIG Summary: Cisco NX-OS Switch RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Apr 2021:

The Cisco perimeter switch must be configured to enforce approved authorizations for controlling the flow of information between interconnected networks in accordance with applicable policy.

DISA Rule

SV-221088r622190_rule

Vulnerability Number

V-221088

Group Title

SRG-NET-000019-RTR-000002

Rule Version

CISC-RT-000250

Severity

CAT II

CCI(s)

• CCI-001414 - The information system enforces approved authorizations for controlling the flow of information between interconnected systems based on organization-defined information flow control policies.

Weight

10

Fix Recommendation

Step 1: Configure an ACL to allow or deny traffic as shown in the example below:

SW2(config)# ip access-list EXTERNAL_ACL
SW2(config-acl)# permit tcp any any established
SW2(config-acl)# permit tcp x.11.1.1/32 eq bgp x.11.1.2/32
SW2(config-acl)# permit tcp x.11.1.1/32 x.11.1.2/32 eq bgp
SW2(config-acl)# permit icmp x.11.1.1/32 x.11.1.2/32 echo
SW2(config-acl)# permit icmp x.11.1.1/32 x.11.1.2/32 echo-reply
SW2(config-acl)# permit tcp any x.11.2.3/32 eq www
SW2(config-acl)# deny ip any any log
SW2(config-acl)# exit

Step 2: Apply the ACL inbound on all applicable interfaces.

SW1(config)#int e2/2
SW1(config-if)# ip access-group EXTERNAL_ACL in

Check Contents

Review the switch configuration to verify that ACLs are configured to allow or deny traffic for specific destination addresses as well as ports and protocols. In the example below, the switch is peering BGP with DISN. ICMP echo and echo-reply packets are allowed for troubleshooting connectivity. WWW traffic is permitted inbound to the NIPRNet host-facing web server (x.11.2.3).

Step 1: Verify that an inbound ACL is applied to all external interfaces as shown in the example below:

interface Ethernet2/2
description link to DISN
no switchport
ip access-group EXTERNAL_ACL in
ip address x.11.1.2 255.255.255.254

Step 2: Review inbound ACL to verify that it is configured to deny all other traffic that is not explicitly allowed.

ip access-list EXTERNAL_ACL
10 permit tcp any any established
20 permit tcp x.11.1.1/32 eq bgp x.11.1.2/32
30 permit tcp x.11.1.1/32 x.11.1.2/32 eq bgp
40 permit icmp x.11.1.1/32 x.11.1.2/32 echo
50 permit icmp x.11.1.1/32 x.11.1.2/32 echo-reply
60 permit tcp any x.11.2.3/32 eq www
70 permit …
…
…
…
90 deny ip any any log

If the switch is not configured to enforce approved authorizations for controlling the flow of information between interconnected networks, this is a finding.

Vulnerability Number

V-221088

Documentable

False

Rule Version

CISC-RT-000250

Severity Override Guidance

Review the switch configuration to verify that ACLs are configured to allow or deny traffic for specific destination addresses as well as ports and protocols. In the example below, the switch is peering BGP with DISN. ICMP echo and echo-reply packets are allowed for troubleshooting connectivity. WWW traffic is permitted inbound to the NIPRNet host-facing web server (x.11.2.3).

Step 1: Verify that an inbound ACL is applied to all external interfaces as shown in the example below:

interface Ethernet2/2
description link to DISN
no switchport
ip access-group EXTERNAL_ACL in
ip address x.11.1.2 255.255.255.254

Step 2: Review inbound ACL to verify that it is configured to deny all other traffic that is not explicitly allowed.

ip access-list EXTERNAL_ACL
10 permit tcp any any established
20 permit tcp x.11.1.1/32 eq bgp x.11.1.2/32
30 permit tcp x.11.1.1/32 x.11.1.2/32 eq bgp
40 permit icmp x.11.1.1/32 x.11.1.2/32 echo
50 permit icmp x.11.1.1/32 x.11.1.2/32 echo-reply
60 permit tcp any x.11.2.3/32 eq www
70 permit …
…
…
…
90 deny ip any any log

If the switch is not configured to enforce approved authorizations for controlling the flow of information between interconnected networks, this is a finding.

Check Content Reference

M

Target Key

4075

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