Network+ Guide to Networks, Fourth Edition Chapter 11 In-Depth TCP/IP Networking Objectives • Understand methods of network design unique to TCP/IP networks, including subnetting, CIDR, NAT and ICS • Explain the differences between public and private networks • Describe protocols used between mail clients and mail servers, including SMTP, POP3, and IMAP4 • Employ multiple TCP/IP utilities for network discovery and troubleshooting Network+ Guide to Networks, 4e 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 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 devices – Improves performance • Data is selectively retransmitted – Simplifies troubleshooting Network+ Guide to Networks, 4e Classful Addressing • Adheres to network class distinctions – Only Class A, B, and C addresses are recognized – Network ID limited to first 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 Classful Addressing (continued) Figure 11-1: Example IP addresses with classful addressing Network+ Guide to Networks, 4e 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 Subnet Masks (continued) Table 11-1: Default subnet masks Network+ Guide to Networks, 4e Subnet Masks (continued) Table 11-2: ANDing Figure 11-2: Example of calculating a host’s network ID Network+ Guide to Networks, 4e Reserved Addresses • Certain types of IP addresses reserved for special functions – In network IDs, bits for host information set to – In broadcast addresses, octet(s) representing host information set to all 1s (255 in decimal notation) Network+ Guide to Networks, 4e 10 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 Traceroute (continued) • Common switches: – -d instructs traceroute not to resolve IP addresses to host names – -h specifies maximum number of hops packets should take when attempting to reach a host • Default is 30 – -w identifies timeout period for responses Network+ Guide to Networks, 4e 39 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 40 Winipcfg • Same as ipconfig utility, but applies to Windows 9x and Me OSs – Graphical interface Network+ Guide to Networks, 4e 41 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 42 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 43 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 44 VoIP (continued) Figure 11-16: Accessing a VoIP network from traditional telephones Network+ Guide to Networks, 4e 45 VoIP (continued) Figure 11-17: Accessing a VoIP network from IP phones Network+ Guide to Networks, 4e 46 Summary • Subnetting separates one network or segment into multiple, logically defined segments, or subnets • Bits in a subnet mask that equal indicate that corresponding bits in an IP address contain network information • Bits in a subnet mask that equal 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 47 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 48 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 49 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 50 ... Block Network+ Guide to Networks, 4e 17 CIDR (continued) Figure 1 1-4 : Subnet mask and supernet mask Figure 1 1-5 : Calculating a host’s network ID on a supernetted network Network+ Guide to Networks,. .. Figure 1 1-1 6: Accessing a VoIP network from traditional telephones Network+ Guide to Networks, 4e 45 VoIP (continued) Figure 1 1-1 7: Accessing a VoIP network from IP phones Network+ Guide to Networks,. .. • To calculate host’s network ID given IP address and subnet mask, perform ANDing Network+ Guide to Networks, 4e Subnet Masks (continued) Table 1 1-1 : Default subnet masks Network+ Guide to Networks,