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Chapter Fifteen

Chapter Fifteen. Linux Networking. Objectives. Describe the purpose and types of networks, protocols, and media access methods Understand basic configuration of TCP/IP protocol Configure a NIC interface to use TCP/IP protocol

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Chapter Fifteen

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  1. Chapter Fifteen Linux Networking

  2. Objectives • Describe the purpose and types of networks, protocols, and media access methods • Understand basic configuration of TCP/IP protocol • Configure a NIC interface to use TCP/IP protocol • Configure a modem, ISDN, and DSL interface to use the PPP and TCP/IP protocols • Understand the purpose of hostnames and how they are resolved to IP addresses • Use common network utilities to interact with network services • Identify and configure common network services

  3. Networks and TCP/IP • Two or more computers connected with media that can exchange information are called a network • Networks that connect computers within close proximity are called Local Area Networks (LANs) • Networks that connect computers separated by large distances are Wide Area Networks (WANs) • Special computers called routers transfer information from one network to another

  4. Networks and TCP/IP • Protocols • Set of rules of communication used between computers on a network • Packets • Packages of data formatted by a network protocol • Media access method • A system that defines how computers on a network share access to the physical medium

  5. Networks and TCP/IP • LAN protocols you may configure in Linux include: • TCP/IP (Transfer Control Protocol/Internet Protocol) • UDP/IP (User Datagram Protocol/Internet Protocol) • IPX/SPX (Internetwork Packet Exchange/Sequence Packet Exchange) • Appletalk • DLC (Data Link Control) • DECnet (Digital Equipment Corporation network)

  6. Networks and TCP/IP • Ethernet • The most common media access method used in networks today • Token Ring • Popular media access method • The media access method is usually contained within the hardware on the NIC or modem

  7. The TCP/IP Protocol • Internet Protocol (IP) address • Series of four 8-bit numbers that represent a computer on a network • Used by a computer on the network to identify itself to other computers • Subnet mask • Series of four 8-bit numbers that determine the network and host portions of an IP address • Default gateway • IP address on router that sends packets to remote networks

  8. The TCP/IP Protocol Figure 15-1: A sample IP address and subnet mask

  9. Configuring a NIC Interface • ifconfig command • Can be used to assign a TCP/IP configuration to a NIC as well as view the configuration of all network interfaces in the computer • packet internet groper (ping) command • Used to check the connectivity on a network

  10. Configuring a NIC Interface Figure 15-2: Configuring network hardware

  11. Configuring a NIC Interface Figure 15-3: Configuring a network device

  12. Configuring a NIC Interface Figure 15-4: Network device properties

  13. Configuring a NIC Interface Figure 15-5: Configuring a network protocol

  14. Configuring a NIC Interface Figure 15-6: Network protocol properties

  15. Configuring a NIC Interface • Linuxconf • Common graphical configuration program that can configure network interfaces • netconfig • Graphical utility used to configure the network card settings of a computer

  16. Configuring a NIC Interface Figure 15-7: The Linuxconf utility

  17. Configuring a NIC Interface Figure 15-8: The netconfig utility

  18. Configuring a PPP Interface • There are three common technologies that use Point-to-Point Protocol (PPP) today to connect computers to a network such as the Internet: • Modems • ISDN • DSL

  19. Configuring a PPP Interface Figure 15-9: Configuring a new PPP device

  20. Configuring a PPP Interface Figure 15-10: Configuring a modem device

  21. Configuring a PPP Interface Figure 15-11: Configuring user account information

  22. Configuring a PPP Interface Figure 15-12: Configuring ISDN hardware

  23. Configuring a PPP Interface Figure 15-13: Configuring user account information

  24. Configuring a PPP Interface Figure 15-14: Configuring a DSL connection

  25. Configuring a PPP Interface Figure 15-15: Activating a PPP connection

  26. Configuring a PPP Interface Figure 15-16: The kppp utility

  27. Name Resolution • Hostnames • User-friendly name assigned to a computer • Fully Qualified Domain Name (FQDN) • Hostname that follows DNS convention • Domain Name Space (DNS) • Network device used t resolve FQDNs to the appropriate IP address

  28. Name Resolution Figure 15-17: The Domain Name Space

  29. Downloading Files Using FTP Figure 15-18: Using a Web browser FTP client

  30. Downloading Files Using FTP Table 15-1: Common FTP commands

  31. Downloading Files Using FTP Table 15-1 (continued): Common FTP commands

  32. Accessing Files with NFS • Network File System (NFS) is another common method for transferring files amongst UNIX and Linux computers • Not as common as FTP • To access files using NFS, you simply mount a directory from a remote computer on the network that has the NFS daemons started to a local directory

  33. Accessing Windows Files • smbmount command • Used to mount directories from Windows computers to mount points from the Internet Super Daemon • smbclient utility • Used to connect to shared resources on a Windows system

  34. Running Remote Applications • On large Linux systems, users typically gain access to a BASH shell by using the utility that connects to the server across the network • The most common utility used to obtain a BASH shell from a remote Linux utility computer on the network is telnet • Trusted access • Configuration where computers are allowed to access a given computer without having to provide a password first

  35. Accessing E-mail Figure 15-19: Configuring a new e-mail account

  36. Accessing E-mail Figure 15-20: Specifying user information

  37. Accessing E-mail Figure 15-21: Configuring a POP, IMAP, and SMTP server

  38. Accessing E-mail Figure 15-22: Specifying a user name

  39. Accessing E-mail Figure 15-23: Specifying an account name

  40. Accessing E-mail Figure 15-24: The Mozilla e-mail client

  41. Common Network Services • Port • Number that uniquely identifies a network service • Well-known port • Of the 65535 possible ports, the ones from 0 to 1024 used by common networking services • Internet Super Daemon (xinetd) • Responsible for initializing and configuring many networking services on a Linux computer

  42. Common Network Services Figure 15-25: Interacting with network services

  43. Common Network Services • Standalone daemons • Daemons normally started at boot-up that configure themselves without assistance from the Internet Super Daemon • The ntsysv utility can be used to configure most standalone daemons to start in various runlevel

  44. Common Network Services Table 15-2: Common network services

  45. Common Network Services Table 15-2 (continued): Common network services

  46. Common Network Services Table 15-2 (continued): Common network services

  47. Common Network Services • Another example of a network service that is provided directly by the Linux kernel is routing • Route table • Table of information used to indicate which networks are connected to network interfaces

  48. Common Network Services • Multihomed hosts • Computer that has more than one network interface • IP forwarding • Act of forwarding TCP/IP packets from one network to another • Routing • Act of forwarding data packets from one network to another

  49. Common Network Services • traceroute command • Common utility used to troubleshoot routing • Displays all routers between the current computer and a remote computer • Some network services involve a large number of daemons and require a great deal of configuration

  50. Chapter Summary • A network is a collection of computers that are connected together and share information • Protocols define the format of information that is transmitted across a network • Each computer on a TCP/IP network must have a valid IP address and subnet mask • The /etc/sysconfig/network-scripts directory contains the configuration for NIC and PPP interfaces

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