This INTEGER marks whether the filter applies to packets arriving (in) or leaving (out) on this virtual router. Getting the direction right matters operationally because the same access-list entry can be meant to police only inbound abuse or only outbound leaks, and applying it to the wrong direction silently filters the wrong traffic. For instance, on VR "vr-finance" an admin blocking inbound telnet attempts would set this filter's direction to 'in' rather than 'out'.