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OS10-RTR-000040 - 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.

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 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.

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

Solution

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 8
OS10(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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Dell_OS10_Switch_Y24M12_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-269852r1051941_rule, STIG-ID|OS10-RTR-000040, Vuln-ID|V-269852

Plugin: Dell_OS10

Control ID: a24e085d2637590dfc8b186b9733cc3b7cd1ee5c517aebf0efcce86ba45892d1