Figure 17-18 Router Firewall: Allowing/Blocking
Certain Apps or Traffic
Domain name proxy: Modern firewalls interact with cloud DNS
servers such as Cisco Umbrella or Open DNS to resolve DNS queries.
The queries and, in turn, the hosts can be stopped at the source if they
are deemed harmful or malicious.Network Diagrams: Bringing It All Together
So far in this chapter, you have learned about all the
elements that constitute a network. The best way to
visually represent a network topology is by using a
network diagram. A network diagram maps out the
structure of a network with different network element
icons and connections between them. This kind of visual
presentation makes it simple and easy for anyone to
understand how a network is built and can help not only
during initial network deployment but also in debugging.
Figure 17-19 shows a typical network topology. At the
core of the network is a router (Router 1) that connects
three different networks. One router interface is
connected to a switch (Switch 1), a second router
interface is connected to a switch (Switch 2), and a third
router interface is connected to a router (Router 2):
Switch 1 connects to Gigabit-ether 0/0 on the router.
Switch 2 connects to Gigabit-ether 0/1 on the router.
Router 2 connects to Fast-ethernet 0/0 on the router.