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

The Cisco BGP router must be configured to reject inbound route advertisements from a customer edge (CE) router for prefixes that are not allocated to that customer.

DISA Rule

SV-216689r531086_rule

Vulnerability Number

V-216689

Group Title

SRG-NET-000018-RTR-000004

Rule Version

CISC-RT-000510

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

Configure the router to reject inbound route advertisements from each CE router for prefixes that are not allocated to that customer.

Step 1: Configure a prefix list for each customer containing prefixes belonging to each.

R1(config)#ip prefix-list PREFIX_FILTER_CUST1 permit x.13.1.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER_CUST1 deny 0.0.0.0/0 ge 8
R1(config)#ip prefix-list PREFIX_FILTER_CUST2 permit x.13.2.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER_CUST2 deny 0.0.0.0/0 ge 8

Step 2: Apply the prefix list filter inbound to each CE neighbor as shown in the example.

R1(config)#router bgp xx
R1(config-router)#neighbor x.12.4.14 prefix-list FILTER_PREFIXES_CUST1 in
R1(config-router)#neighbor x.12.4.16 prefix-list FILTER_PREFIXES_CUST2 in

Check Contents

Review the router configuration to verify that there are ACLs defined to only accept routes for prefixes that belong to specific customers.

Step 1: Verify prefix list has been configured for each customer containing prefixes belonging to each customer as shown in the example below:

ip prefix-list PREFIX_FILTER_CUST1 seq 5 permit x.13.1.0/24 le 32
ip prefix-list PREFIX_FILTER_CUST1 seq 10 deny 0.0.0.0/0 ge 8
ip prefix-list PREFIX_FILTER_CUST2 seq 5 permit x.13.2.0/24 le 32
ip prefix-list PREFIX_FILTER_CUST2 seq 10 deny 0.0.0.0/0 ge 8

Step 2: Verify that the prefix lists has been applied to all to the applicable CE peers as shown in the example below:

router bgp xx
no synchronization
bgp log-neighbor-changes
neighbor x.12.4.14 remote-as 64514
neighbor x.12.4.14 prefix-list FILTER_PREFIXES_CUST1 in
neighbor x.12.4.16 remote-as 64516
neighbor x.12.4.16 prefix-list FILTER_PREFIXES_CUST2 in

Note: Routes to PE-CE links within a VPN are needed for troubleshooting end-to-end connectivity across the MPLS/IP backbone. Hence, these prefixes are an exception to this requirement.

If the router is not configured to reject inbound route advertisements from each CE router for prefixes that are not allocated to that customer, this is a finding.

Vulnerability Number

V-216689

Documentable

False

Rule Version

CISC-RT-000510

Severity Override Guidance

Review the router configuration to verify that there are ACLs defined to only accept routes for prefixes that belong to specific customers.

Step 1: Verify prefix list has been configured for each customer containing prefixes belonging to each customer as shown in the example below:

ip prefix-list PREFIX_FILTER_CUST1 seq 5 permit x.13.1.0/24 le 32
ip prefix-list PREFIX_FILTER_CUST1 seq 10 deny 0.0.0.0/0 ge 8
ip prefix-list PREFIX_FILTER_CUST2 seq 5 permit x.13.2.0/24 le 32
ip prefix-list PREFIX_FILTER_CUST2 seq 10 deny 0.0.0.0/0 ge 8

Step 2: Verify that the prefix lists has been applied to all to the applicable CE peers as shown in the example below:

router bgp xx
no synchronization
bgp log-neighbor-changes
neighbor x.12.4.14 remote-as 64514
neighbor x.12.4.14 prefix-list FILTER_PREFIXES_CUST1 in
neighbor x.12.4.16 remote-as 64516
neighbor x.12.4.16 prefix-list FILTER_PREFIXES_CUST2 in

Note: Routes to PE-CE links within a VPN are needed for troubleshooting end-to-end connectivity across the MPLS/IP backbone. Hence, these prefixes are an exception to this requirement.

If the router is not configured to reject inbound route advertisements from each CE router for prefixes that are not allocated to that customer, this is a finding.

Check Content Reference

M

Target Key

4028

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