company, NAT can be used, but both the source and the destination IP addresses will need to be
translated. For instance, consider Figure 5-26, with Company A using a network that is
registered to Cisco (170.1.0.0):
the packet would never get to the real 170.1.1.1 in Cisco's network. That is because there is a
very reasonable possibility that the private network has a route matching 170.1.1.1 in its routing
table that points to some subnet inside the private company. So, when the DNS reply comes
back past the NAT router, the DNS reply is changed by NAT so that the client in Company A
thinks www.cisco.com's IP address is 192.168.1.1. NAT not only translates the source IP
address in outgoing packets, but it also translates the destination. Likewise, packets returning
to Company A have both the source and the destination IP addresses changed.
summarizes the terminology and meaning.
5-26
needed, this address is typically a private address or an
address in a network registered to another organization.
address. This address is in a network registered to the
company responsible for the NAT router.
host correctly attached to the Internet.