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

The Cisco BGP switch must be configured to reject inbound route advertisements for any prefixes belonging to the local autonomous system (AS).

DISA Rule

SV-221024r622190_rule

Vulnerability Number

V-221024

Group Title

SRG-NET-000018-RTR-000003

Rule Version

CISC-RT-000500

Severity

CAT II

CCI(s)

• CCI-001368 - The information system enforces approved authorizations for controlling the flow of information within the system based on organization-defined information flow control policies.

Weight

10

Fix Recommendation

Review the switch configuration to verify that it will reject routes belonging to the local AS.

Configure the router to reject inbound route advertisements for any prefixes belonging to the local AS.

Step 1: Add to the prefix filter list those prefixes belonging to the local autonomous system.

SW1(config)#ip prefix-list PREFIX_FILTER seq 74 deny x.13.1.0/24 le 32

Step 2: If not already completed to be compliant with previous requirement, apply the prefix list filter inbound to each external BGP neighbor as shown in the example.

SW1(config)#switch bgp xx
SW1(config-switch)#neighbor x.1.1.9 prefix-list PREFIX_FILTER in
SW1(config-switch)#neighbor x.2.1.7 prefix-list PREFIX_FILTER in
SW1(config-switch)#end

Check Contents

Review the switch configuration to verify that it will reject routes belonging to the local AS.

Step 1: Verify a prefix list has been configured containing prefixes belonging to the local AS. In the example below x.13.1.0/24 is the global address space allocated to the local AS.

ip prefix-list PREFIX_FILTER seq 5 deny 0.0.0.0/8 le 32
…
…
…
ip prefix-list PREFIX_FILTER seq 74 deny x.13.1.0/24 le 32
ip prefix-list PREFIX_FILTER seq 75 permit 0.0.0.0/0 ge 8

Step 2: Verify that the prefix list has been applied to all external BGP peers as shown in the example below:

router bgp xx
no synchronization
bgp log-neighbor-changes
neighbor x.1.1.9 remote-as yy
neighbor x.1.1.9 prefix-list PREFIX_FILTER in
neighbor x.2.1.7 remote-as zz
neighbor x.2.1.7 prefix-list PREFIX_FILTER in

If the switch is not configured to reject inbound route advertisements belonging to the local AS, this is a finding.

Vulnerability Number

V-221024

Documentable

False

Rule Version

CISC-RT-000500

Severity Override Guidance

Review the switch configuration to verify that it will reject routes belonging to the local AS.

Step 1: Verify a prefix list has been configured containing prefixes belonging to the local AS. In the example below x.13.1.0/24 is the global address space allocated to the local AS.

ip prefix-list PREFIX_FILTER seq 5 deny 0.0.0.0/8 le 32
…
…
…
ip prefix-list PREFIX_FILTER seq 74 deny x.13.1.0/24 le 32
ip prefix-list PREFIX_FILTER seq 75 permit 0.0.0.0/0 ge 8

Step 2: Verify that the prefix list has been applied to all external BGP peers as shown in the example below:

router bgp xx
no synchronization
bgp log-neighbor-changes
neighbor x.1.1.9 remote-as yy
neighbor x.1.1.9 prefix-list PREFIX_FILTER in
neighbor x.2.1.7 remote-as zz
neighbor x.2.1.7 prefix-list PREFIX_FILTER in

If the switch is not configured to reject inbound route advertisements belonging to the local AS, this is a finding.

Check Content Reference

M

Target Key

4074

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