The Dell OS10 BGP router must be configured to reject outbound route advertisements for any prefixes that do not belong to any customers or the local autonomous system (AS).
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-269853 | OS10-RTR-000050 | SV-269853r1051944_rule | Medium |
| Description |
| Advertisement of routes by an autonomous system for networks that do not belong to any of its customers pulls traffic away from the authorized network. This causes a denial of service (DoS) on the network that allocated the block of addresses and may cause a DoS on the network that is inadvertently advertising it as the originator. It is also possible that a misconfigured or compromised router within the GIG IP core could redistribute IGP routes into BGP, thereby leaking internal routes. |
| STIG | Date |
| Dell OS10 Switch Router Security Technical Implementation Guide | 2024-12-11 |
Details
| Check Text (C-73886r1051942_chk) |
| This requirement is not applicable for the DODIN Backbone. Review the router configuration to verify that there is a filter defined to only advertise routes for prefixes that belong to any customers or the local AS. The prefix filter must be referenced outbound on the appropriate BGP neighbor statements. Step 1: Verify prefix lists have been configured for each customer containing prefixes that belong to that customer. OS10# show running-configuration prefix-list ! ... ip prefix-list PREFIX_FILTER_A seq 5 permit 50.10.10.0/24 le 32 ip prefix-list PREFIX_FILTER_A seq 10 permit 60.10.10.0/24 le 32 ip prefix-list PREFIX_FILTER_A seq 15 deny 0.0.0.0/0 ge 8 ... Step 2: Verify the route map applied to the external neighbors references the configured prefix list shown above. OS10# show running-configuration route-map ! route-map PREFIX_FILTER_A_MAP permit 50 match ip address prefix-list PREFIX_FILTER_A Step 3: Verify the route map applied to the external neighbors references the appropriate route maps shown above. ! router bgp 10 ! neighbor 50.1.1.1 ! address-family ipv4 unicast route-map PREFIX_FILTER_A_MAP out If the router is not configured to reject outbound route advertisements that belong to any customers or the local AS, this is a finding. |
| Fix Text (F-73787r1051943_fix) |
| Configure all eBGP routers to filter outbound route advertisements for prefixes that are not allocated to or belong to any customer or the local AS. Step 1: Configure a prefix list for each customer containing prefixes belonging to each. OS10(config)# ip prefix-list PREFIX_FILTER_A seq 5 permit 50.10.10.0/24 le 32 OS10(config)# ip prefix-list PREFIX_FILTER_A seq 10 permit 60.10.10.0/24 le 32 OS10(config)# ip prefix-list PREFIX_FILTER_A seq 15 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_A_MAP 50 OS10(config-route-map)# match ip address prefix-list PREFIX_FILTER_A OS10(config-route-map)# exit Step 3: Apply the route-map outbound 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_A_MAP out OS10(config-router-bgp-neighbor-af)# exit OS10(config-router-neighbor)# exit OS10(config-router-bgp-10)# exit |