V-283906

Discussion

Access control lists (ACLs) are used to separate data traffic into traffic that will be routed (permitted packets) and traffic that will not be routed (denied packets). Secure configuration of routers uses access lists for restricting access to services on the router and filtering traffic passing through the router. Inbound versus Outbound: Some operating systems' default access lists are applied to the outbound queue. The more secure solution is to apply the access list to the inbound queue for three reasons: - The router can protect itself before damage is inflicted. - The input port is still known and can be filtered on. - It is more efficient to filter packets before routing them.

Check Content

This requirement is not applicable for the DODIN Backbone.

Review the router configuration to verify the ingress ACL is bound to the external interface in an inbound direction.

To verify all interfaces have the ingress filter assigned, verify fields "Ingress Filter" and "Ingr IPv6 Flt" for all interfaces using the command below:

- show router interface "TO-PE2" detail | match "Ingress Filter"

Egress Filter    : 10                   Ingress Filter    : 10

- show router interface "TO-PE2" detail | match "Ingr IPv6 Flt"

Egr IPv6 Flt     : 20                   Ingr IPv6 Flt     : 20

If the router is not configured to filter traffic entering the network at the external interface in an inbound direction, this is a finding.