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Network+ Guide to Networks, Fourth Edition

Network+ Guide to Networks, Fourth Edition. Chapter 11 In-Depth TCP/IP Networking. Designing TCP/IP-Based Networks. Review of some TCP/IP fundamentals: IP is a routable protocol On a network using TCP/IP, each interface associated with unique IP address

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Network+ Guide to Networks, Fourth Edition

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  1. Network+ Guide to Networks, Fourth Edition Chapter 11 In-Depth TCP/IP Networking

  2. Designing TCP/IP-Based Networks • Review of some TCP/IP fundamentals: • IP is a routable protocol • On a network using TCP/IP, each interface associated with unique IP address • Some nodes may use multiple IP addresses • IP addresses consist of four 8-bit octets • Many networks assign IP addresses and host names dynamically, using DHCP • Every IP address can be associated with a network class Network+ Guide to Networks, 4e

  3. Subnetting • Separates network into multiple, logically defined segments (subnets) • Each subnet’s traffic separated from every other subnet’s traffic • Enhances security • Subnetworks must be connected via routers or other Layer 3 devices • Improves performance • Data is selectively retransmitted • Simplifies troubleshooting Network+ Guide to Networks, 4e

  4. Classful Addressing • Adheres to network class distinctions • Only Class A, B, and C addresses are recognized • Network ID limited to first 8 bits in Class A, first 16 bits in Class B, and first 24 bits in Class C • Fixed network ID size ultimately limits number of hosts a network can include Network+ Guide to Networks, 4e

  5. Classful Addressing (continued) Figure 11-1: Example IP addresses with classful addressing Network+ Guide to Networks, 4e

  6. Subnet Masks • Subnetting depends on subnet masks to identify how a network is subdivided • Indicates where network information is located in an IP address • “1” bits indicate corresponding bits in IP address contain network information • “0” bits indicate corresponding bits in IP address contain host information • To calculate host’s network ID given IP address and subnet mask, perform ANDing Network+ Guide to Networks, 4e

  7. Subnet Masks (continued) Table 11-1: Default subnet masks Network+ Guide to Networks, 4e

  8. Subnet Masks (continued) Table 11-2: ANDing Figure 11-2: Example of calculating a host’s network ID Network+ Guide to Networks, 4e

  9. Reserved Addresses • Certain types of IP addresses reserved for special functions • In network IDs, bits for host information set to 0 • In broadcast addresses, octet(s) representing host information set to all 1s (255 in decimal notation) Network+ Guide to Networks, 4e

  10. Subnetting Techniques • Subnetting breaks rules of classful addressing • Some bits that in classful addressing would represent host information changed to represent network information • Reduce number of usable host addresses per subnet Network+ Guide to Networks, 4e

  11. Subnetting Techniques (continued) Table 11-3: Class B subnet masks Network+ Guide to Networks, 4e

  12. Subnetting Techniques (continued) Table 11-4: Class C subnet masks Network+ Guide to Networks, 4e

  13. Calculating Subnets • Formula for determining how to modify a default subnet mask: 2n-2=Y • n = number of bits in subnet mask that must be switched from 0 to 1 • Y = number of subnets that result • Extended network prefix: Additional bits used for subnet information plus existing network ID • Class A, B, and C networks can all be subnetted • External routers pay attention to only the network portion of devices’ IP addresses Network+ Guide to Networks, 4e

  14. Calculating Subnets (continued) Figure 11-3: A router connecting several subnets Network+ Guide to Networks, 4e

  15. Calculating Subnets (continued) Figure 11-3 (continued): A router connecting several subnets Network+ Guide to Networks, 4e

  16. CIDR (Classless Interdomain Routing) • Classless routing or supernetting • Provides additional ways of arranging network and host information in an IP address • Supernet: Subnet created by moving subnet boundary to the left • Generates more usable IP addresses • CIDR notation (slash notation): network ID followed by forward slash (/), followed by number of bits used for extended network prefix • CIDR Block Network+ Guide to Networks, 4e

  17. CIDR (continued) Figure 11-4: Subnet mask and supernet mask Figure 11-5: Calculating a host’s network ID on a supernetted network Network+ Guide to Networks, 4e

  18. Internet Gateways • Combination of software and hardware enabling two different network segments to exchange data • Every device on a TCP/IP-based network has a default gateway • First interprets outbound requests to other subnets • Interprets inbound requests from other subnets • Each node on network has one default gateway • May be network interface on a router • Must maintain routing tables as well • Core gateways make up the Internet backbone Network+ Guide to Networks, 4e

  19. Internet Gateways (continued) Figure 11-6: The use of default gateways Network+ Guide to Networks, 4e

  20. NAT (Network Address Translation) • Default gateways can be used to “hide” IP numbers assigned within an organization • Clients behind gateway may use any IP addressing scheme • Even non-legitimate schemes • Must have legitimate IP address to exchange data with Internet • NAT: when client’s transmission reaches default gateway, it assigns client’s transmission a valid IP address Network+ Guide to Networks, 4e

  21. NAT (continued) Figure 11-7: NAT through an Internet gateway Network+ Guide to Networks, 4e

  22. ICS (Internet Connection Sharing) • Computer with Internet access (ICS host) configured to translate requests to and from Internet on behalf of other computers on network • Acts as DHCP server, DNS resolver, and NAT gateway for clients on its LAN • Network adapter on ICS host assigned IP address of 192.168.0.1 • Clients must be set up to obtain IP addresses automatically • ICS host assigns clients IP addresses in range of 192.168.0.2 through 192.168.0.255 Network+ Guide to Networks, 4e

  23. Intranets and Extranets • Intranet: network or part of network that uses browser-based services to exchange information within an enterprise • Used for supplying HTTP-accessible documents, e-mail, file sharing, document management, and collaboration • Defined by its security policies • Extranet: network that uses Internet-like services and protocols to exchange information within an organization and with certain, authorized users outside of that organization Network+ Guide to Networks, 4e

  24. TCP/IP Mail Services • E-mail is most frequently used Internet service that network administrators manage • Mail servers communicate with other mail servers to deliver messages across Internet • Hundreds of software packages for mail servers exist • Sendmail, Microsoft Exchange Server, Lotus Notes, Novell Groupwise • Mail clients send/retrieve messages to/from mail servers • Servers and clients communicate through TCP/IP Application layer protocols Network+ Guide to Networks, 4e

  25. SMTP (Simple Mail Transfer Protocol) • Protocol responsible for moving messages between mail servers over TCP/IP-based networks • Belongs to Application layer of TCP/IP Model • Relies on TCP at Transport layer • Operates from port 25 • Relies on higher-level programs for instructions • Can only transport or hold mail • When configuring clients to use Internet e-mail, must identify user’s SMTP server Network+ Guide to Networks, 4e

  26. MIME (Multipurpose Internet Mail Extensions) • Standard SMTP message format allows for lines that contain 1000 ASCII characters max • Cannot handle pictures or formatted text • MIME: standard for encoding and interpreting binary files, images, video, and non-ASCII character sets within e-mail messages • Identifies each element of a message according to content type • Works in conjunction with SMTP Network+ Guide to Networks, 4e

  27. POP (Post Office Protocol) • Application layer protocol used to retrieve messages from mail servers • POP3 is most current and commonly used version • Mail delivered and stored on mail server until user connects (via e-mail client) to retrieve messages • Mail deleted from server after retrieval • Minimizes use of server resources • Best suited to users who retrieve mail from same workstation all the time Network+ Guide to Networks, 4e

  28. IMAP (Internet Message Access Protocol) • Developed as sophisticated alternative to POP3 • IMAP4 is most current version • Users can store messages on mail server • IMAP4 provides the following features: • Retrieve all or only a portion of any mail message • Review messages and delete them while the messages remain on the server • Create sophisticated methods of organizing messages on the server • Share mailboxes in a central location Network+ Guide to Networks, 4e

  29. Additional TCP/IP Utilities • TCP/IP comes with complete set of utilities that can help to track down most TCP/IP-related problems • e.g., Ping, Telnet, ARP • Nearly all TCP/IP utilities can be accessed from command prompt on any type of server or client running TCP/IP • Syntax may differ depending on OS • Options may differ according to OS Network+ Guide to Networks, 4e

  30. Netstat • Displays TCP/IP statistics and details about TCP/IP components and connections on a host • Port on which a particular TCP/IP service is running • Network connections currently established • Number of packets handled by network interface since activation • Number of data errors Network+ Guide to Networks, 4e

  31. Netstat (continued) • Common Netstat switches: • -a lists all available TCP and UDP connections • -e displays details about all packets that have been sent • -n lists currently connected hosts according to their ports and IP addresses (in numerical form) • -p allows you to specify what type of protocol statistics to list • -r provides list of routing table information • -s provides statistics about each packet transmitted by a host, separated according to protocol type Network+ Guide to Networks, 4e

  32. Nbtstat • Given NetBIOS name, get IP address • Common nbtstat switches: • -a displays a machine’s name table given its NetBIOS name • -A displays a machine’s name table given its IP address • -r lists statistics about names that have been resolved to IP addresses by broadcast and by WINS • -s displays a list of all the current NetBIOS sessions for a machine Network+ Guide to Networks, 4e

  33. Nslookup • Query DNS database from any network computer and find host name of a device by specifying its IP address, or vice versa • Provides host’s IP address, primary DNS server name, and address holding record for this name • Many options (switches) Network+ Guide to Networks, 4e

  34. Dig • Domain information groper (dig): similar to nslookup • Provides more detailed information than nslookup • e.g., specifics about resource records associated with host name • Many switches • Must be explicitly installed on Windows systems Network+ Guide to Networks, 4e

  35. Dig (continued) Figure 11-11: Output of a simple dig command Network+ Guide to Networks, 4e

  36. Whois • Query DNS registration database and obtain information about a domain • Who is domain registered to? • Technical person responsible for domain? • Hosting entity? • DNS Server addresses? • Must install software to use on Windows systems • Web-based alternatives exist • e.g., www.arin.net Network+ Guide to Networks, 4e

  37. Traceroute (Tracert) • Uses ICMP to trace path from one node to another • Identifies all intermediate hops • Useful for determining router or subnet connectivity problems • Transmits series of UDP datagrams to specified destination • Increases TTL as path is discovered • Traceroute may stop before completing • Device problem on path • Device does not accept ICMP transmissions • Often indicates firewall Network+ Guide to Networks, 4e

  38. Ipconfig • TCP/IP administration utility for use with Windows NT, 2000, XP, and Server 2003 OSs • Provides information about network adapter’s IP address, subnet mask, and default gateway • Commonly used switches: • /? displays list of available switches • /all displays complete TCP/IP configuration information for each network interface on device • /release releases DHCP-assigned addresses for all network interfaces • /renew renews DHCP-assigned addresses for all network interfaces Network+ Guide to Networks, 4e

  39. Winipcfg • Same as ipconfig utility, but applies to Windows 9x and Me OSs • Graphical interface Network+ Guide to Networks, 4e

  40. Ifconfig • TCP/IP configuration and management utility used on UNIX-type of systems • Similar to ipconfig on Windows systems • Commonly used switches: • -a applies command to all interfaces on a device • down marks interface as unavailable to network • up reinitializes interface after it has been taken “down” • Complete list of switches found in man pages Network+ Guide to Networks, 4e

  41. VoIP (Voice over IP) • Use of packet-switched networks and TCP/IP to transmit voice conversations • IP telephony • Objectives for implementing VoIP: • Lower costs for voice calls • Supply new or enhanced features and applications • Centralize voice and data network management Network+ Guide to Networks, 4e

  42. VoIP (continued) • VoIP callers can use: • Traditional telephone • IP telephones: telephones designed for TCP/IP transmission • Softphones: computers equipped with microphone, speaker, and VoIP client software • IP telephones must have unique IP addresses • More difficult to transmit voice signals over a packet-switched network than data signals • Internet telephony: VoIP carried via Internet • May also be carried over private lines Network+ Guide to Networks, 4e

  43. VoIP (continued) Figure 11-16: Accessing a VoIP network from traditional telephones Network+ Guide to Networks, 4e

  44. Summary • Subnetting separates one network or segment into multiple, logically defined segments, or subnets • Bits in a subnet mask that equal 1 indicate that corresponding bits in an IP address contain network information • Bits in a subnet mask that equal 0 indicate that corresponding bits in an IP address contain host information • CIDR allows the creation of supernets, or subnets established by using bits that normally would be reserved for network class information Network+ Guide to Networks, 4e

  45. Summary (continued) • Gateways facilitate communication between different subnets • Every device on a TCP/IP-based network has a default gateway • NAT allows a network administrator to “hide” IP addresses assigned to nodes on a private network • ICS is a service that allows a network of computers to share a single Internet connection through an ICS host computer Network+ Guide to Networks, 4e

  46. Summary (continued) • SMTP is responsible for moving messages from one e-mail server to another over TCP/IP-based networks • POP is a mail retrieval protocol • IMAP4 allows users to store messages on the mail server, rather than always having to download them to the local machine • The netstat utility displays TCP/IP statistics and the state of current TCP/IP components and connections Network+ Guide to Networks, 4e

  47. Summary (continued) • The nslookup utility allows you to look up the DNS host name of a network node by specifying the node’s IP address, or vice versa • The traceroute utility useful for determining router or subnet connectivity problems • VoIP is the use of packet-switched TCP/IP-based networks to carry voice signals Network+ Guide to Networks, 4e

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