Which command is used to activate an IPv4 ACL named SALES on an interface so that the router filters traffic prior to it accessing the routing table?
- ipv4 access-class SALES out
- ip access-class SALES in
- ipv4 access-group SALES out
- ip access-group SALES in
Explanation: To filter traffic before it reaches the routing table, you must apply the ACL in the inbound direction using the ip access-group command. According to the sources, an inbound ACL processes incoming packets before they are routed to an outbound interface. This is considered efficient because it saves the router the overhead of performing a routing lookup if the packet is destined to be discarded by the ACL anyway.
If the ACL were applied in the outbound direction (using the out keyword), the router would first have to route the packet to the outbound interface before checking it against the ACL. Additionally, the command access-class is specifically used for controlling access to vty lines rather than physical interfaces. Therefore, ip access-group SALES in is the correct command to achieve pre-routing filtering for a named IPv4 ACL on an interface.
Related exam: Modules 14 – 16: Checkpoint Exam: Network Security Answers (CCNP ENCOR v9)
