CNT-2311-Chapter 8 Notes - Revision history

Vang3636: /* Chapter 8 */

2011-03-27T23:22:24Z

Chapter 8

← Older revision		Revision as of 23:22, 27 March 2011
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	~~===~~= Chapter 8 =~~===~~		= Chapter 8 =

	== Network Hardware Configuration ==		== Network Hardware Configuration ==
	::-The most basic part of network configuration is getting the network hardware up and running.		::-The most basic part of network configuration is getting the network hardware up and running.

Vang3636: /* Ifup and ifdown command (pg. 408) /

2011-03-27T23:21:58Z

Ifup and ifdown command *(pg. 408)

← Older revision		Revision as of 23:21, 27 March 2011
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			==== Chapter 8 ====
			== Network Hardware Configuration ==
			::-The most basic part of network configuration is getting the network hardware up and running.
			::-Most of the time that is a fairly automatic task since most systems ship with startup scripts that auto-detect the ::network card and loads the correct driver module.
			::-If the network hardware is not detected subsequent configuration will not work. You will need to load your network ::hardware driver.
			::-You will use the modprobe command. You must know the name of the networks hardware kernel module.
			:: # modprobe <insert kernel name here>
			== Configuring with DHCP==
			::-One of the most easy ways to configure a computer to use a TCP/IP network is to use DHCP. This allows one computer on ::a network to manage the settings for many other computers.
			::-When a computer running a DHCP client boots up it send out a broadcast looking for a DHCP server. The server then ::replies with the configuration information needed by the client to communicate with the computers on the network.
			::-Linux has three common DHCP clients.
			::: pump
			::: dhclient
			::: dhcpcd
			::-Some distributions ship with one of these but others ship with two or all three. They will all have a default DHCP ::client, that is installed when you tell the system you want to use DHCP at the installation.
			::-On systems that ship with more then one DHCP client you can swap one out for another by removing the old client and ::installing the package for the new one.
			::-The DHCP client runs at system bootup and is handled by its own SysV startup file or as part of the main network ::configuration startup file.
			::-This SysV file is typically named networking or network.
			::-The system uses a line in a configuration file to determine whether to run a DHCP client.
			::-Red Hat and Fedora set this option in a file called /etc/sysconfig/network-scripts/ifcfg-eth0 (the filename will be ::different if something other than a single Ethernet interface is used)
			::-The line in question looks like this: BOOTPROTO=dhcp
			::-If the BOOTPROTO variable is set to something different changing to the above line will set the system to use DHCP.
			::-Ubuntu uses the /etc/network/interfaces file for a similar purpose but the details differ.
			::-On a system that uses DHCP you will see a line like: iface eth0 inet dhcp
			::-You may prefer to use the GUI system to adjust these options.
			::-Once the DHCP client is configured to run when the system boots the configuration task is complete. On rare occasions ::you may need to tweak the DHCP settings to work around client/server incompatibilities.
			::-If you have to manually run a DHCP client you can do so by typing its name (as root) followed by a network identifier ::such as: dhclient eth0 to have the DHCP client attempt to configure eth0 with the help of any DHCP server it find on the
			::network.
			== Configure with a Static IP Address ==
			::-When a network lacks a DHCP server you will need to provide basic network configuration options manually.
			::-These options can be set using interactive commands but to sent them long term you need to adjust a configuration file ::such as:
			::/etc/sysconfig/ network-scripts/ifcfg-eth0 or /etc/network/interfaces

			::-IP address: You can set the IP address manually with the ifconfig command or at the IPADDR line in the configuration ::file.
			::-Network mask: You can set the netmask manually with the ifconfig command or at the NETMASK line in the configuration ::file.
			::-Gateway address: You can manually set the gateway via the route command. To make it permanent you need to adjust the ::configuration file. This file may be the same that holds other options or another file such as: /etc/sysconfig/
			::network/routes and is most likely called GATEWAY.
			::-DNS settings: In order for Linux to use DNS to translate between IP addresses and hostnames you must specify at least ::one DNS server in the /etc/resolv.config file. Adjusting this file is all you need to do to set the name server address.
			::-You can also set your computers local domain name in this file using the domain option: domain <name of the domain you ::want to use>
			::-The network configuration script may hold other options such as:
			::DEVICE=eth0 to specify the interface name
			::BOOTPROTO=static to assign a static IP address
			::ONBOOT=yes to bring up an interface when the system boots
			::NETWORK and BROADCAST are derived from the IPADDR and NETMASK and can be changed if you understand the consequences of ::doing so.
			::-This command will bring up eth0 using address 192.168.29.39 and netmask 255.255.255.0
			::# ifconfig etho up 192.168.29.39 netmask 255.255.255.0
			::-This command links the specified address to the card so that the computer responds to the address and claims to be that ::address when sending data.
			::-Both ifconfig and route can display information on the current network configuration.
			::-For ifconfig, omit up and everything that follows; for route, omit add everything that follows.
			::-To view the interface you may use this command: # ifconfig eth0
			::-When configured correctly ifconfig should show a hardware address an IP address and some other statistics.
			== Configuring Routing ==
			::-Routers pass traffic from one network to another. You give the computer a routers address which your system uses as a ::gateway to the internet.
			::-Any traffic not directed to the network is directed to the router which then sends it on to it’s destination. Every ::router has a list of rules concerning where to send data based on the destination IP address.
			::-The –net and –host force route to interpret the target as a network or computer address, respectively.
			::-Netmask lets you set a netmask as you desire and gw lets you specify a router through which packets to the specified ::target should go.
			::-The reject keyword installs a blocking route , which refuses all traffic destined for the specific network.
			::-Incorrect routing tables can cause serious problems causing some or all computers on the network not to respond. You ::can use route alone to compare the results to what your routing table should be.

	== Ifup and ifdown command *(pg. 408) ==		== Ifup and ifdown command *(pg. 408) ==

Vang3636: /* Tracepath command (pg. 413) /

2011-03-24T22:12:07Z

Tracepath command *(pg. 413)

← Older revision		Revision as of 22:12, 24 March 2011
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	== Tracepath command *(pg. 413) ==		== Tracepath command *(pg. 413) ==
	::- This command is a lot similar to traceroute		::- This command is a lot similar to traceroute

			== Checking Network Status ==
			::-A useful diagnostic tool is Netstat
			::-Netstat can be used in place of many other tools.
			::-It also shows information that is not easily found in other ways.

			== Netstat options ==
			::-Interface information: use netstat –interface or -i parameter to see information about
			::network interfaces. This is similar to what ifconfig command displays
			::-Routing information: use netstat –route or -r parameter to see the routing table. This
			::output is similar to what the route command shows
			::-Masquerade information: use netstat –masquerade or –M to see information about
			::connections mediated by Linux’s NAT features . This is a good way to stretch limited
			::IPv4 addresses.
			::-Program use: use netstat –program or –p parameter to show information about programs that
			::are using network connections.
			::-All connections: use netstat –all or –a parameter to display information about the ports
			::that server programs open to listen for network connections.

			== tcpdump ==
			::-Advanced network troubleshooting tool.
			::-tcpdump is a packet sniffer that intercepts network packets and log them on the screen.
			::-Useful tool to verify that computer is receiving data from other computers
			::-This is also useful to examine the data in its raw form, which can be helpful if you
			::-understand protocols implementation details allowing you to spot problems.
			::-Be aware that packet sniffers can be used by individuals to capture passwords sent over
			::the network.
			::-You must use tcpdump in root mode.
			::-Once you enter tcpdump it summarizes what it is doing and prints lines, one for each packet
			::it monitors.
			::-Lines consist of time stamps, stack identifiers, origin system name, IP addresses and
			::port, destination system name and packet-specific information.
			::-Once tcpdump starts it dose not stop so you must press Ctrl+C to terminate it.

			== tcpdump options ==
			::- A: displays packet contents in ASCII
			::- D: Displays a list of interfaces tcpdump can listen to.
			::- n: Shows all addresses numerically.
			::- v: Shows additional packet information.
			::- w file: Used to write captured packets to the specified file.
			::-You could consult tcpdump’s man page for details and for additional options.

			== Additional Networking Tools ==
			::-Other than networking diagnostic programs you could use some common programs as debugging tools.
			::-One of the most helpful tools may be Telnet a program and protocol tool that is mainly used as
			::a remote login tool.
			::-Telnet is considered a poor choice as a remote login protocol due to the fact that it
			::is entirely unencrypted.
			::-A good rule to follow is that you should remove Telnet server from your system and never use
			::the telnet client program. SSH is a safer alternative to Telnet described in chapter 10.

			== Using Telnet to Debug Network Protocols ==
			::-If you include a port number after the remote hostname, the program connects to the
			::specified port allowing you to interact with the server.
			::-To use telnet this way you must know a lot of information about the protocol. Without
			::the knowledge of the protocol you can still use Telnet to test if a server is running or not.
			::-If you try to connect and get a connection refused error message you know that a remote
			::server is not running or is inaccessible. (This may be because a firewall is blocking
			::the connection)
			::-If the result is Escape character this means that the server is running, even though it
			::could not be working correctly.
			::-This test only works for protocols that us TCP. UDP tools will not connect.

			== Using Telnet to Debug Network Protocols continued ==
			::-Sometimes File Transfer Protocols (FTP) can be a helpful tool.
			::-This program allows you to transfer files between systems, as its name suggests.
			::-To use this tool type the program name followed by the FTP servers name, which will then
			::show you a login prompt, allowing you to issue FTP commands.

Vang3636: Created page with "== Ifup and ifdown command (pg. 408) == ::-The ifup command bring the interface up ::-The ifdown command bring the interface down == Example of ifup/ifdown (pag.408) == ::“..."

2011-03-23T19:55:21Z

Created page with "== Ifup and ifdown command *(pg. 408) == ::-The ifup command bring the interface up ::-The ifdown command bring the interface down == Example of ifup/ifdown *(pag.408) == ::“..."

New page

== Ifup and ifdown command *(pg. 408) ==

::-The ifup command bring the interface up
::-The ifdown command bring the interface down

== Example of ifup/ifdown *(pag.408) ==
::“ifup eth0”
::–bring up the interface eth0“ifdown eth0”.
::–bring down the interface eth0- useful to quickly to take down a interface or
::bring it up, because you do not need to remember all the detail of the IP
::address, route and so on.

== Hostnames *(pg. 409) ==
::There are 2 way to configure the hostname
::-On DNS
::-On you local computer

== Domain Name System (DNS) *(pg. 409) ==
::- “is a distributed database computers that converts between IP addresses and
::hostnames”.
::- The DNS server just sit and listen for other computers on the network to send
::request.
::- The server then send the request out to other DNS server if it cannot find it
::in it cache.
::- If the server found what the request is asking for then it will send a request
::back to the computer telling it where to go.

== Diagnosing Network Connections *(pg. 412) ==
::- There are a few command that will help diagnose a problem.
::- They are ping, traceroute, tracepath, netstat, and tcpdump.

== Ping command *(pg. 412) ==
:- The ping command is a very basic network test, which send ICMP packet to the
:system you name, hostnames, or ip address and wait for a reply
:- In Linux it send the packet every second until you press Ctrl+C key to stop
:the stroke.

== Traceroute command *(pg. 412-413) ==
::- This command will sends a series of three test packets to each computer
::between your system and a specified target system

== Tracepath command *(pg. 413) ==
::- This command is a lot similar to traceroute

CNT-2311-Chapter 8 Notes - Revision history

Vang3636: /* Chapter 8 */

Vang3636: /* Ifup and ifdown command *(pg. 408) */

Vang3636: /* Tracepath command *(pg. 413) */

Vang3636: Created page with "== Ifup and ifdown command *(pg. 408) == ::-The ifup command bring the interface up ::-The ifdown command bring the interface down == Example of ifup/ifdown *(pag.408) == ::“..."

Vang3636: /* Ifup and ifdown command (pg. 408) /

Vang3636: /* Tracepath command (pg. 413) /

Vang3636: Created page with "== Ifup and ifdown command (pg. 408) == ::-The ifup command bring the interface up ::-The ifdown command bring the interface down == Example of ifup/ifdown (pag.408) == ::“..."