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 deny network traffic by default and allow network traffic by exception.

DISA Rule

SV-221087r622190_rule

Vulnerability Number

V-221087

Group Title

SRG-NET-000202-RTR-000001

Rule Version

CISC-RT-000240

Severity

CAT I

CCI(s)

• CCI-001109 - The information system at managed interfaces denies network communications traffic by default and allows network communications traffic by exception (i.e., deny all, permit by exception).

Weight

10

Fix Recommendation

Step 1: Configure an inbound ACL to deny all other traffic by default 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)# permit tcp any x.11.2.3/32 eq www
SW1(config-acl)# permit …
…
…
…
SW1(config-acl)# deny ip any any log

Step 2: Apply the ingress filter to all external interfaces.

SW1(config)#int e1/2
SW1(config-if)#ip access-group EXTERNAL_ACL in

Check Contents

Review the switch configuration to verify that the inbound ACL applied to all external interfaces is configured to allow specific ports and protocols and deny all other traffic.

Step 1: Verify that an inbound ACL is applied to all external interfaces 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

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 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 permit tcp any x.11.2.3/32 eq www
60 permit …
…
…
…
90 deny ip any any log

If the ACL is not configured to allow specific ports and protocols and deny all other traffic, this is a finding. If the ACL is not configured inbound on all external interfaces, this is a finding.

Vulnerability Number

V-221087

Documentable

False

Rule Version

CISC-RT-000240

Severity Override Guidance

Review the switch configuration to verify that the inbound ACL applied to all external interfaces is configured to allow specific ports and protocols and deny all other traffic.

Step 1: Verify that an inbound ACL is applied to all external interfaces 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

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 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 permit tcp any x.11.2.3/32 eq www
60 permit …
…
…
…
90 deny ip any any log

If the ACL is not configured to allow specific ports and protocols and deny all other traffic, this is a finding. If the ACL is not configured inbound on all external interfaces, this is a finding.

Check Content Reference

M

Target Key

4075

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