Managing Network connections

Network Cabling

Ethernet Topology Bus topology – Connects each node in a line – Has no central connection point Star topology – Connects all nodes to a centralized hub – More popular; easier to maintain

Ethernet Topology

Ethernet Using Star Topology

Ethernet Using Star Bus Topology

Repeaters

Wireless LANs (WLANs) Make connections using a wireless NIC Communicate directly or connect to a LAN by way of a wireless access point (AP) Popular where cables are difficult to install Slower than wired networks Security is an issue Standards – 1999 IEEE b (Wi-Fi, AirPort) – Bluetooth

Bridges and Switches Bridges – Send broadcast messages; not good for large networks – Effective at separating high- volume areas on a LAN – Work best when used to connect LANs that usually do not communicate outside their immediate network Switches – Send a packet only to network segment for which it is destined

Bridges Compared with Switches

MAC Addresses Unique addresses that are permanently embedded in a NIC and identify a device on a LAN Expressed as six pairs of hexadecimal numbers and letters A local address Used at the lowest (physical) networking level for NICs and other devices on the same network to communicate

12 Architectural Overview of the TCP/IP 12

The TCP/IP Protocols The TCP/IP protocols – Provide networking connectivity support for computers (called hosts) on LANs and WANs – Follow a set of standards for how computers communicate and how networks are interconnected – Follow the four-layer Department of Defense (DOD) model

14 Internet Protocol Internet Protocol (IP) does the actual delivery of datagrams. IP adds the following header fields to each packet: Source IP Address Destination IP Address Protocol Checksum Time to Live (TTL)

15 IP Addressing Every host on a TCP/IP network must have a unique IP address (a 32-bit number that identifies both the host and the network the host is located on). IP addresses are expressed in dotted-decimal format, such as Each set of four dotted-decimal numbers represents eight bits of the binary address. – The addresses range from to , or, in decimal notation, from 0 to 255.

16 IP Addressing (Cont.) An IP address is accompanied by a subnet mask. The subnet mask, when compared to the IP address, identifies the part of the IP address that is the network identifier and the part that is the host identifier. – The 1s identify network bits and the 0s identify host bits. – In the subnet mask , the first 16 bits (2 octets) are the equivalent of all ones in binary form. The first two octets of the IP address are the network identifier. The last two octets represent the host identifier.

17 IP Address Classes

18 IP Address Ranges for Private Networks ClassNetwork Addresses A through B through C through

19 Using Ipconfig.exe Use Ipconfig.exe to view the TCP/IP configuration settings on a host, including IP address, subnet mask, and default gateway. – At the command prompt, type ipconfig or ipconfig /all and then press Enter. – Use the /all parameter to display more information. Running Ipconfig is an easy way to view the IP address and other parameters that the DHCP server has assigned to your computer.

20 Using Ping Ping is a command-line utility that uses Echo Request messages to determine if the TCP/IP stack of another computer on the network is functioning normally. From a command prompt, type ping target (where target is the IP address or the name [DNS or NetBIOS, Example ping of the computer you are trying to contact). – A successful ping results in several reply messages from the target computer. – If the ping fails, one or both computers might have a networking hardware or software problem. – Example c:\> ping

21 Using Traceroute Tracert.exe, a variant of Ping, displays the path that packets take to their destination. From a command prompt, type tracert target (where target is the IP address or the name [DNS or NetBIOS] of the target computer). Use Tracert.exe to isolate the location of a network communications problem, particularly when a router is suspected. Example C:\> tracert.exe

22 Using Pathping Pathping is a route tracing tool that – Sends packets to each router on the way to a final destination over a period of time – Computes results based on the packets returned from each hop You can use Pathping.exe to isolate problems because it shows the degree of packet loss at any given router or link. From the command line, type pathping target (where target is the IP address or the name [DNS or NetBIOS] of the target computer). Example C:\> pathping.exe

23 Using Route.exe (Cont.) The ROUTE PRINT command displays the current contents of the routing table. To create a new entry, use ROUTE ADD with parameters that specify the values for the entry. Example C:\> route.exe

24 Using Route.exe Use Route.exe to create, delete, or modify static routes in a routing table on a computer running Windows Route.exe uses the following syntax: ROUTE [-f] [-p][command[destination] [MASK netmask] [gateway] [METRIC metric] [IF interface]] The Route.exe command variable takes one of four values: PRINT ADD DELETE CHANGE

25 Using Arp.exe IP uses ARP to discover the hardware address that each datagram is transmitted to. Resolved addresses are stored in an ARP cache. Use Arp.exe to view or change the contents of the ARP cache. Arp.exe uses the following syntax: ARP [-a {ipaddress}] [-n ipaddress] [- s ipaddress hwaddress {interface}] [-d ipaddress {interface}]

26 Using Netstat.exe Netstat.exe is a Windows 2000 command-line utility that displays information about – The current network connections of a computer using TCP/IP – The traffic generated by various TCP/IP protocols Netstat.exe uses the following syntax: NETSTAT [interval] [-a] [-p protocol] [-n] [-e] [-r] [-s]

27 Using Nbtstat.exe Nbtstat.exe is a Windows 2000 command-line utility that displays information about the NetBIOS over TCP/IP connections used by Windows 2000 when communicating with other Windows computers on a TCP/IP LAN. Nbtstat.exe uses the following syntax: NBTSTAT [-a name] [-A ipaddress] [-c] [-n] [-r] [-R] [-s] [-S] [-RR] The parameters for Nbtstat.exe are case- sensitive.

28 Using Nslookup.exe Nslookup.exe is a Windows 2000 command- line utility that enables you to generate DNS request messages and transmit them to a specific DNS server on the network. Nslookup.exe uses the following syntax: NSLOOKUP DNSname DNSserver – DNSname specifies the DNS name you want to resolve. – DNSserver specifies the DNS name (or IP address of the DNS server) you want to query for the name you want to resolve.

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