OS10-RTR-000100 - The Dell OS10 BGP router must be configured to reject route advertisements from CE routers with an originating autonomous system (AS) in the AS_PATH attribute that does not belong to that customer.

Information

Verifying the path a route has traversed will ensure that the local AS is not used as a transit network for unauthorized traffic. To ensure that the local AS does not carry any prefixes that do not belong to any customers, all PE routers must be configured to reject routes with an originating AS other than that belonging to the customer.

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

Solution

Configure the router to reject updates from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer.

Step 1: Configure a prefix list for each customer containing prefixes belonging to each.

OS10(config)# ip as-path access-list AS_PATH_FILTER_CUST1 permit 10.*
OS10(config)# ip as-path access-list AS_PATH_FILTER_CUST1 deny .*
OS10(config)# ip as-path access-list AS_PATH_FILTER_CUST2 permit 200
OS10(config)# ip as-path access-list AS_PATH_FILTER_CUST2 deny .*

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

OS10(config)# route-map AS_PATH_FILTER_CUST1_MAP 50
OS10(config-route-map)# match ip address prefix-list AS_PATH_FILTER_CUST1
OS10(config-route-map)# exit
OS10(config)# route-map AS_PATH_FILTER_CUST2_MAP 50
OS10(config-route-map)# match ip address prefix-list AS_PATH_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 AS_PATH_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 AS_PATH_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|III, CCI|CCI-001368, Rule-ID|SV-269855r1051950_rule, STIG-ID|OS10-RTR-000100, Vuln-ID|V-269855

Plugin: Dell_OS10

Control ID: 1d56abf70eb03cd5bbdb3544b0fb529aad24a7f65438308e1cc5163fbfc22f53