Exam N10-007 topic 1 question 352 discussion

The correct answer is A. Transport. The router also can perform packet filtering at the transport layer based on the source and destination TCP or UDP port. THe standard IP access control list on a Cisco router functions at OSI Layer 3, and an extended IP ACL functions at Layers 3 and 4. https://networkustad.com/2019/09/02/what-is-an-access-control-list-acl/ http://etutorials.org/Networking/Router+firewall+security/Part+I+Security+Overview+and+Firewalls/Chapter+2.+Introduction+to+Firewalls/Controlling+Traffic+and+the+OSI+Reference+Model

An ACL can apply to Layer 4 (the protocol layer), Layer 7 (the application layer), or both. A Layer 4 or Layer 7 ACL is used with network access, application access, or web access connections. it could be layer 7

Commonly, an ACL is associated with the filtering of IP packets (Network Layer 3 of the OSI Model) as they pass through a router. In other words, it is used to permit or deny traffic through a router the answer is network layer

Can someone explain why the answer isn't B - Network layer? Routers are generally understood to operate at Layer 3 of the OSI model. I assume the given answer is because the question mentions port numbers?