Title

The Juniper BGP router must be configured to reject route advertisements from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer. (Cat III impact)

Discussion

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.

Check Content

This requirement is not applicable for the DODIN Backbone.” Review the router configuration to verify the router is configured to deny updates received from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer. Step 1: Verify a policy has been configured to filter AS_PATH attribute for received BGP advertisements as shown in the example below: policy-options { … … … policy-statement FILTER_ASx { term ALLOW_ASx { from as-path PEER_ASx; then accept; } term ELSE_REJECT { then reject; } } … … … as-path PEER_ASx "^x$"; } Note: the characters “^” and “$” representing the beginning and the end of the expression respectively are optional and are implicitly defined if omitted. Step 2: Verify that the import policy has been applied to all external BGP peers as shown in the example below: protocols { bgp { group GROUP_ASx { type external; import [ FILTER_ASx FILTER_ROUTES ]; peer-as x; neighbor x.x.x.x; } If the router is not configured to reject updates from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer, this is a finding.

Fix Text

Step 1: Configure a policy to filter the AS_PATH as shown in the example below: [edit policy-options] set as-path PEER_ASx "^x$" set policy-statement FILTER_ASx term ALLOW_ASx from as-path PEER_ASx set policy-statement FILTER_ASx term ALLOW_ASx then accept set policy-statement FILTER_ASx term ELSE_REJECT then reject Step 2: Apply the import policy as shown in the example below: [edit protocols bgp group GROUP_ASx] set import [FILTER_AS4 FILTER_ROUTES]

Additional Identifiers

Rule ID: SV-217059r945855_rule

Vulnerability ID: V-217059

Group Title: SRG-NET-000018-RTR-000010

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.