The simplest form of a firewall is a packet filtering firewall.

The simplest form of a firewall is a packet filtering firewall. Typically, a router works as a packet-filtering firewall and has the capability to filter on some of the contents of packets.

On which of the following layers of the Open System Interconnection (OSI) reference model do these routers filter information?

Each correct answer represents a complete solution. (Choose all that apply.)