TODAYINTERNET ADDRESSINGTCIP/IPNAT, IP, TCP, UDP, CONFIGURATION, DNS, DHCP, WINSLAB 8: CONFIGURE DHCP SERVER

NETWORK ADDRESS TRANSLATION (NAT)

Allows unregistered private network addresses to communicate with legally registered IP addresses

Advantages Hides internal IP addresses, thus providing security Eliminates need for multiple registered IP addresses Allows multiple ISDN (Integrated Services Digital Network) connections

to be combined into one Internet connection

IP CONFIGURATION

DOMAIN NAME SYSTEM (DNS)

Makes it easy to identify and find hosts on Internet When domain name is entered, it is converted to its IP

address

FULLY QUALIFIED DOMAIN NAME (FQDN)

Needed to locate a host on a large network Example of an FQDN: station2.xyzcorp.com*A combination of the host name and domain name.

Operating systems such as Linux, and Windows 2000 and later follow the rules of Fully Qualified Domain Names when creating their network structure.

(FQDN VS NETBIOS NAME)

Fully Qualified Domain Name is limited to 63 characters. NetBIOS names is a computer name limited to 15

characters. Many symbols allowed in NetBIOS names cannot be

used in FQDN.

(;:”<>*+=\/?,) To allow for communication between legacy systems

and ones that use host names the computer names are converted automatically.

DNS STRUCTURE AND OPERATION Hierarchical structure

Root - The authoritative name servers that serve the DNS root zone

Top-level domains—.com,.edu,.gov,.net,.org

Second-level domains—mit.eduSubdomains(any level domain located

beneath the secondary domain)—campus.mit.edu, faculty.mit.edu

AKA (lower-level domain)

DNS STRUCTURE AND OPERATION Resolver A software program located on a host that queries a

DNS server to resolve a host name to an IP address

Research .mit.edu• DNS server the

host is connected to as part of a workgroup or domain.

• OR it could be an ISP

• Domain names are placed in cache for future requests.

• If not in cache Top level DNS is contacted

• If top level server cannot resolve request it is passed on to the root sever

• Once information is found it is returned to the resolver

WINDOWS INTERNET NAMING SERVICE (WINS)

Windows NT server operating systems used WINS to resolve NetBIOS names to IP addresses

Windows 2000 and later use the Dynamic DNS, which incorporates the WINS and DNS features

IP, TCP, AND UDP Three most commonly used protocols in TCP/IP suite IP establishes a link between nodes but does not verify

the data is delivered correctly – connectionless protocol TCP ensures packets arrive intact and in correct order -

connection-oriented TCP can break large amounts of data into smaller

packets and UDP cannot UDP sends a single packet to transmit control

information and data - connectionless protocol

TCP OR UDPThe selection of TCP or UDP depends on

three factorsThe software used in the upper layers

of the OSI modelThe amount of data to be sentIf a connectionless or connection-

oriented transport of data is desired

OSI MODEL AND TCP/IP

UDP FRAMEUDP and TCP Rely on the IP Frame format for IP address Destination and source

Used to transfer small blocks of data and commands

TCP FRAME

Used to reassemble data in a correct order

IP FRAMEFinal step is to encapsulate the entire set of protocol frames in a frame matching the network standard e.g Ethernet

ASSIGNING IP ADDRESSES Static addressing or dynamic addressing can be used to

assign IP addresses to hosts A static IP assignment is entered manually when the NIC

is configured A server running the Dynamic Host Configuration

Protocol (DHCP) issues an IP address to a host when it joins the network

(dynamic IP assignment) an IP address that is issued automatically. Typically when a computer boots and joins the network.

The default DHCP IP lease period is 8 days.

DYNAMIC ADDRESSING

AUTOMATIC PRIVATE IP ADDRESSING (APIPA)

Used when the host is unable to access a DHCP server Host automatically generates an IP address in the range

of 169.254.0.1 to 169.254.255.254 Uses the APIPA address to communicate with other

workstations on the same segment. This addressing is compatible with all Microsoft products

starting with Windows 98 This was not necessary in previous operating systems

due to NetBEUI protocol which uses MAC addresses to communicate with workstations on the same segment

TCP/IP PORTS AND SOCKET

A port number combined with an IP address (socket) is used to create a virtual connection

E.G. 192.168.20.45:80 Socket technology allows multiple, simultaneous

services to run between a server and a workstation.

EXAMPLES OF WELL-KNOWN PORT NUMBERS

Service or Protocol Port Number

FTP 20, 21

SSH 22

Telnet 23

SMTP 25

DNS 53

TFTP 69

HTTP 80

POP3 110

NNTP 119

NTP 123

IMAP4 143

HTTPS 443