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.
An XCCDF Rule
Description
<VulnDiscussion>As a best practice, a service provider should only accept customer prefixes that have been assigned to that customer and any peering autonomous systems. A multi-homed customer with BGP speaking routers connected to the Internet or other external networks could be breached and used to launch a prefix de-aggregation attack. Without ingress route filtering of customers, the effectiveness of such an attack could impact the entire IP core and its customers.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-216689r917428_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
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