to ensure that the nearby router receives the frame.
network layer address groupings. As shown in Table 3-10 later in this section, these groupings
vary based on the network layer protocol type. The router compares the destination network
layer address in the packet to the entries in the routing table in memory, and a match is made.
This matching entry in the routing table tells this router where to forward the packet next.
address in the packet identifies the group in which the destination resides. The routing table is
searched for a matching entry, which tells this router where to forward the packet next.
Eventually, the packet is delivered to the router connected to the network or subnet of the
destination host, as previously shown in Figure 3-17.
the destination of the packet are in the same L3 grouping. That final router can forward the data
directly to the destination. As usual, a new data link header and trailer are created before a frame
(which contains the packet that made the trip across the entire network) can be sent on to the
media. This matches the final step (Step 3), as previously shown in Figure 3-17.
contain data link addresses, the routers must have some way to decide what data link addresses
to use. An example of how the router determines which data link address to use is the IP Address
Resolution Protocol (ARP) protocol. ARP is used to dynamically learn the data link address of
some IP host.
that PC1 is sending packets to PC2. (If you do not understand the basics of IP addressing
already, you may want to bookmark this page and refer to it after you have reviewed Chapter 5,
which covers IP addressing.) Figure 3-18 provides an example network so that you can review
the routing process.