Title

The BGP router must be configured to reject route advertisements from BGP peers that do not list their autonomous system (AS) number as the first AS in the AS_PATH attribute. (Cat III impact)

Discussion

Verifying the path a route has traversed will ensure the IP core is not used as a transit network for unauthorized or possibly even Internet traffic. All autonomous system boundary routers (ASBRs) must ensure updates received from eBGP peers list their AS number as the first AS in the AS_PATH attribute.

Check Content

Review the router configuration to verify the router is configured to deny updates received from eBGP peers that do not list their AS number as the first AS in the AS_PATH attribute. If the router is not configured to reject updates from peers that do not list their AS number as the first AS in the AS_PATH attribute, this is a finding.

Fix Text

Configure all ASBRs to deny updates received from eBGP peers that do not list their AS number as the first AS in the AS_PATH attribute.

Additional Identifiers

Rule ID: SV-207102r945854_rule

Vulnerability ID: V-207102

Group Title: SRG-NET-000018

Expert Comments

CCIs tied to check.

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