ARST-RT-000040 - The Arista 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.

Information

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.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

Step 1: Configure Arista eBGP routers to reject inbound route advertisements from a CE router for prefixes that are not allocated to that specific customer.

LEAF-1A(config)#ip access-list BGP_Enclave_Gateway_Filter_IN
LEAF-1A(config-acl-BGP_Enclave_Gateway_Filter_IN)# 10 permit ip 172.16.50.0/30 any
LEAF-1A(config-acl-BGP_Enclave_Gateway_Filter_IN)# 20 permit ip 10.1.1.0/24 any
LEAF-1A(config-acl-BGP_Enclave_Gateway_Filter_IN)# 30 permit ip 12.15.4.9/32 any
LEAF-1A(config-acl-BGP_Enclave_Gateway_Filter_IN)# 40 deny ip any any log

Step 2: Configure a route-map to match the ACL.

LEAF-1A(config-ip-pfx)#route-map FILTER_INBOUND permit 10
LEAF-1A(config-route-map-FILTER_INBOUND)#match ip address access-list BGP_Enclave_Gateway_Filter_IN

Step 3: Configure the route-map to be applied inbound to the appropriate CE customer neighbor.

LEAF-1A(config)#router bgp 65001
LEAF-1A(config-router-bgp)#neighbor 100.2.1.1 route-map FILTER_INBOUND in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Arista_MLS_EOS_4-2x_Y24M07_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-255990r882312_rule, STIG-ID|ARST-RT-000040, Vuln-ID|V-255990

Plugin: Arista

Control ID: 51ce3ef8ed9c2ed3a85f9ad27fbb0d73bdbd3cff019c6bdc33c08c0d5ea043f0