Hannah is in IP network 8.0.0.0, and R1 is the only router
that's connected to that IP network. Because Hannah knows that routers know how
to route packets, it makes sense that Hannah should forward the packet to R1.
However, there are several little details that are important to note in Figure 11-2. First, Hannah's PC knows its
default router by the IP address, not by the name. Routers typically have one IP
address per physical interface; Hannah needs to know R1's IP address on R1's
Ethernet1 interface in this case, because R1's
Ethernet1 interface is connected to the same Ethernet LAN that Hannah is.
(Because routers have lots of interfaces of many different types, routers label
the physical interfaces with a name and a number, such as Ethernet1.)
|
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Although the term "default router" makes sense, most people use
the term "default gateway" to mean the same thing. Before the term "router"
became popular, people called the same kind of device a "gateway." Oddly enough,
although almost everyone uses the term "router" when speaking of a hardware
device that performs routing, many people still use the term "default gateway,"
whereas others use "default
router." | |
The last details to point out have to do with how the packet
gets from Hannah to R1. Notice in Figure
11-2 that Hannah's IP address (8.1.1.1) is listed as the source and
www.example.com's IP address (130.4.3.3) is listed as the destination. So, how
does Hannah get the packet to R1? Well, there are a few things to cover to get
the full story, including encapsulation and a protocol called Address Resolution Protocol (ARP),
which you will learn about in the next sections.
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