STIGQter: STIG Summary: Cisco IOS XR Router RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Oct 2020:

The Cisco perimeter router must be configured to deny network traffic by default and allow network traffic by exception.

DISA Rule

SV-216752r531087_rule

Vulnerability Number

V-216752

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

This requirement is not applicable for the DODIN Backbone.

Step 1: Configure an inbound ACL to deny all other traffic by default as shown in the example below.

RP/0/0/CPU0:R3(config)#ipv4 access-list EXTERNAL_ACL_INBOUND
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp host x.11.1.1 eq bgp host x.11.1.2
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp host x.11.1.1 host x.11.1.2 eq bgp
RP/0/0/CPU0:R3(config-ipv4-acl)#permit icmp host x.11.1.1 host x.11.1.2 echo
RP/0/0/CPU0:R3(config-ipv4-acl)#permit icmp host x.11.1.1 host x.11.1.2 echo-reply
RP/0/0/CPU0:R3(config-ipv4-acl)#deny ip any host x.11.1.1 log-input
RP/0/0/CPU0:R3(config-ipv4-acl)#permit tcp any any established
…
…
…
RP/0/0/CPU0:R3(config-ipv4-acl)#deny ip any any log-input
RP/0/0/CPU0:R3(config-ipv4-acl)#exit

Step 2: Apply the ingress filter to all external interfaces

RP/0/0/CPU0:R3(config)#int g0/0/0/1
RP/0/0/CPU0:R3(config-if)#ipv4 access-group EXTERNAL_ACL_INBOUND in
RP/0/0/CPU0:R3(config-if)#end

Check Contents

This requirement is not applicable for the DODIN Backbone.

Review the router 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 GigabitEthernet0/0/0/1
ipv4 address x.11.1.2 255.255.255.252
ipv4 access-group EXTERNAL_ACL_INBOUND ingress

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

ipv4 access-list EXTERNAL_ACL_INBOUND
10 permit tcp host x.11.1.1 eq bgp host x.11.1.2
20 permit tcp host x.11.1.1 host x.11.1.2 eq bgp
30 permit icmp host x.11.1.1 host x.11.1.2 echo
40 permit icmp host x.11.1.1 host x.11.1.2 echo-reply
50 deny ipv4 any host x.11.1.1 log-input
60 permit tcp any any established
…
…
…
140 deny ipv4 any any log-input

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-216752

Documentable

False

Rule Version

CISC-RT-000240

Severity Override Guidance

This requirement is not applicable for the DODIN Backbone.

Review the router 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 GigabitEthernet0/0/0/1
ipv4 address x.11.1.2 255.255.255.252
ipv4 access-group EXTERNAL_ACL_INBOUND ingress

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

ipv4 access-list EXTERNAL_ACL_INBOUND
10 permit tcp host x.11.1.1 eq bgp host x.11.1.2
20 permit tcp host x.11.1.1 host x.11.1.2 eq bgp
30 permit icmp host x.11.1.1 host x.11.1.2 echo
40 permit icmp host x.11.1.1 host x.11.1.2 echo-reply
50 deny ipv4 any host x.11.1.1 log-input
60 permit tcp any any established
…
…
…
140 deny ipv4 any any log-input

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

4029

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