Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

Understanding Basic IP Routing 103
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The NAT device tracks each translation (conversation) between the source
host (inside network) and the destination host (outside network), and vice
versa and stores them in internal tables.
Some router vendors call NAT tables as translation tables. Cisco calls them
xlate on their PIX firewalls.
NAT converts IP addresses from the private address space to the public
address space.
NAT is a method by which IP addresses are mapped from one address realm
to another.
This translation provides transparent routing from host to host.
Port address translation (PAT) translates transport identifiers like TCP and
UDP port numbers and ICMP query identifiers.
Summary of Exam Objectives
TCP/IP is a suite of protocols that provides the functionality specified in the OSI
model using the four related layers of the Department of Defense model: network
interface, Internet, host-to-host, and application.
IP addresses are 32-bit addresses represented in dotted decimal format (w.x.y.z).
The 32 bits contain both a network and host ID. When sending data, the IP
address in the packet is compared, using bitwise ANDing, to the subnet mask.
The packet is sent to the appropriate internal or external location depending on
the results of the ANDing process.
Network addresses were originally designed in a class-based system. Class A with
an address range of 1.x.y.z to 126.x.y.z, Class B with an address range of 128.0.y.z
to 191.255.y.z, and Class C with an address range of 192.0.0.z to 223.255.255.z.
The default subnet masks are: Class A: 255.0.0.0; Class B: 255.255.0.0; and Class
C: 255.255.255.0.
Classful networks can be subdivided into subnets using custom subnet masks.
There is an inverse relationship between the number of subnets and the number
of hosts per subnet.
Packets destined for networks that are not local are forwarded using gateways or
routers. IP routing involves resolving the hostname or NetBIOS name to an IP
address and resolving the IP address to a MAC address. NetBIOS name resolution
uses four different node types to resolve names to IP addresses: broadcast
(B-node), peer-to-peer (P-node), mixed (M-node), and hybrid (H-node). Names
can also be resolved by using a HOSTS file or through the DNS or in the case
of NetBIOS names with an LMHOSTS file or through WINS. The ARP is used
to resolve the IP address to the MAC address that is unique to each Network
Interface Card (NIC) manufactured.
Routing on a network can be static or dynamic. Four commonly used routing
utilities are route, ping, tracert, and pathping. Protocols such as APIPA and
DHCP help to get systems logically addressed dynamically. In this chapter, we