The Cisco BGP switch must be configured to reject inbound route advertisements from a customer edge (CE) switch for prefixes that are not allocated to that customer.
An XCCDF Rule
Description
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 switches 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.
- ID
- SV-221105r999714_rule
- Version
- CISC-RT-000510
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Configure the switch to reject inbound route advertisements from each CE switch for prefixes that are not allocated to that customer.
Step 1: Configure a prefix list for each customer containing prefixes belonging to each.
SW1(config)# ip prefix-list PREFIX_FILTER_CUST1 permit x.13.1.0/24 le 32
SW1(config)# ip prefix-list PREFIX_FILTER_CUST1 deny 0.0.0.0/0 ge 8