The Dell OS10 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

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 multihomed customer with BGP speaking routers connected to the internet or other external networks could be breached and used to launch a prefix deaggregation attack. Without ingress route filtering of customers, the effectiveness of such an attack could impact the entire IP core and its customers.

ID: SV-269852r1051941_rule
Version: OS10-RTR-000040
Severity: Medium
References: CCI-001368
Updated: about 2 months ago

Remediation Templates

Configure all eBGP routers to reject inbound route advertisements from a 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.

OS10(config)# ip prefix-list PREFIX_FILTER_CUST1 seq 5 permit 50.10.10.0/24 le 32
OS10(config)# ip prefix-list PREFIX_FILTER_CUST1 seq 10 deny 0.0.0.0/0 ge 8OS10(config)# ip prefix-list PREFIX_FILTER_CUST2 seq 5 permit 60.10.10.0/24 le 32
OS10(config)# ip prefix-list PREFIX_FILTER_CUST2 seq 10 deny 0.0.0.0/0 ge 8

Step 2: Configure the route map referencing the configured prefix list.

OS10(config)# route-map PREFIX_FILTER_CUST1_MAP 50
OS10(config-route-map)# match ip address prefix-list PREFIX_FILTER_CUST1
OS10(config-route-map)# exit
OS10(config)# route-map PREFIX_FILTER_CUST2_MAP 50
OS10(config-route-map)# match ip address prefix-list PREFIX_FILTER_CUST2
OS10(config-route-map)# exit

Step 3: Apply the route-map inbound to each external BGP neighbor.

OS10(config)# router bgp 10
OS10(config-router-bgp-10)# neighbor 50.1.1.1
OS10(config-router-neighbor)# address-family ipv4 unicast
OS10(config-router-bgp-neighbor-af)# route-map PREFIX_FILTER_CUST1_MAP in
OS10(config-router-bgp-neighbor-af)# exit
OS10(config-router-neighbor)# exit
OS10(config-router-bgp-10)# neighbor 60.1.1.1
OS10(config-router-neighbor)# address-family ipv4 unicast
OS10(config-router-bgp-neighbor-af)# route-map PREFIX_FILTER_CUST2_MAP in
OS10(config-router-bgp-neighbor-af)# exit
OS10(config-router-neighbor)# exit
OS10(config-router-bgp-10)# exit

The Dell OS10 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.

Description

Remediation Templates

A Manual Procedure