|  |  | A packet filtering router may act as part of a firewall. A Cisco router can filter packets in several ways: The first filtering point to consider is the IP address in the IP layer. A packet filtering router can accept or reject packets based on the source or destination IP address. The host to host layer. It may filter access to or from certain services, allowing or denying tftp, telnet access, and ftp access. Established connection. It can allow connections that have originated from within the protected network but block all those originating outside.