Now that you have a basic understanding of ACL configuration and their additional features, the rest of this chapter focuses on some important filtering rules that you should implement on your router. In this section, I assume that your router is acting either as a perimeter router or as the main perimeter firewall.
A bogon is a network or route prefix that should not appear in an Internet routing table. Many types of bogon addresses exist, including the following:
• Addresses that should be used only internally, such as RFC 1918 addresses.
• Loopback addresses (127.0.0.0/8).
• Reserved IANA addresses.
• Multicast addresses (18.104.22.168/4).
• Research addresses (240.0.0.0/4).
• DHCP local ...