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diff --git a/slackbook/html/network-configuration-tcpip.html b/slackbook/html/network-configuration-tcpip.html new file mode 100644 index 00000000..3b49437e --- /dev/null +++ b/slackbook/html/network-configuration-tcpip.html @@ -0,0 +1,324 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org" /> +<title>TCP/IP Configuration</title> +<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /> +<link rel="HOME" title="Slackware Linux Essentials" href="index.html" /> +<link rel="UP" title="Network Configuration" href="network-configuration.html" /> +<link rel="PREVIOUS" title="Network Hardware Configuration" +href="network-configuration-hardware.html" /> +<link rel="NEXT" title="PPP" href="network-configuration-ppp.html" /> +<link rel="STYLESHEET" type="text/css" href="docbook.css" /> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> +</head> +<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084" +alink="#0000FF"> +<div class="NAVHEADER"> +<table summary="Header navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<th colspan="3" align="center">Slackware Linux Essentials</th> +</tr> + +<tr> +<td width="10%" align="left" valign="bottom"><a +href="network-configuration-hardware.html" accesskey="P">Prev</a></td> +<td width="80%" align="center" valign="bottom">Chapter 5 Network Configuration</td> +<td width="10%" align="right" valign="bottom"><a href="network-configuration-ppp.html" +accesskey="N">Next</a></td> +</tr> +</table> + +<hr align="LEFT" width="100%" /> +</div> + +<div class="SECT1"> +<h1 class="SECT1"><a id="NETWORK-CONFIGURATION-TCPIP" +name="NETWORK-CONFIGURATION-TCPIP">5.3 TCP/IP Configuration</a></h1> + +<p>At this point, your network card should be physically installed in your computer, and +the relevant kernel modules should be loaded. You will not yet be able to communicate +over your network card, but information about the network device can be obtained with <tt +class="COMMAND">ifconfig -a</tt>.</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">ifconfig -a</kbd> +eth0 Link encap:Ethernet HWaddr 00:A0:CC:3C:60:A4 +UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 +RX packets:110081 errors:1 dropped:0 overruns:0 frame:0 +TX packets:84931 errors:0 dropped:0 overruns:0 carrier:0 +collisions:0 txqueuelen:100 +RX bytes:114824506 (109.5 Mb) TX bytes:9337924 (8.9 Mb) +Interrupt:5 Base address:0x8400 + +lo Link encap:Local Loopback +inet addr:127.0.0.1 Mask:255.0.0.0 +UP LOOPBACK RUNNING MTU:16436 Metric:1 +RX packets:2234 errors:0 dropped:0 overruns:0 frame:0 +TX packets:2234 errors:0 dropped:0 overruns:0 carrier:0 +collisions:0 txqueuelen:0 +RX bytes:168758 (164.8 Kb) TX bytes:168758 (164.8 Kb) +</pre> +</td> +</tr> +</table> + +<p>If you just typed <tt class="COMMAND">/sbin/ifconfig</tt> without the <var +class="OPTION">-a</var> suffix, you would not see the <tt class="FILENAME">eth0</tt> +interface, as your network card does not yet have a valid IP address or route.</p> + +<p>While there are many different ways to setup and subnet a network, all of them can be +broken down into two types: Static and Dynamic. Static networks are setup such that each +node (geek lingo for thing with an IP address) always has the same IP address. Dynamic +networks are setup in such a way that the IP addresses for the nodes are controlled by a +single server called the DHCP server.</p> + +<div class="SECT2"> +<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-TCPIP-DHCP" +name="NETWORK-CONFIGURATION-TCPIP-DHCP">5.3.1 DHCP</a></h2> + +<p>DHCP (or Dynamic Host Configuration Protocol), is a means by which an IP address may +be assigned to a computer on boot. When the DHCP <span class="emphasis"><i +class="EMPHASIS">client</i></span> boots, it puts out a request on the Local Area Network +for a DHCP <span class="emphasis"><i class="EMPHASIS">server</i></span> to assign it an +IP address. The DHCP server has a pool (or <span class="emphasis"><i +class="EMPHASIS">scope</i></span>) of IP addresses available. The server will respond to +this request with an IP address from the pool, along with a <span class="emphasis"><i +class="EMPHASIS">lease time</i></span>. Once the lease time for a given IP address lease +has expired, the client must contact the server again and repeat the negotiation.</p> + +<p>The client will then accept the IP address from the server and will configure the +requested interface with the IP address. There is one more handy trick that DHCP clients +use for negotiating the IP address that they will be assigned, however. The client will +remember it's last assigned IP address, and will request that the server re-assign that +IP address to the client again upon next negotiation. If possible, the server will do so, +but if not, a new address is assigned. So, the negotiation resembles the following:</p> + +<p class="LITERALLAYOUT"> <span class="emphasis"><i +class="EMPHASIS">Client</i></span>: Is there a DHCP server available on the LAN?<br /> + + <span class="emphasis"><i +class="EMPHASIS">Server</i></span>: Yes, there is. Here I am.<br /> + + <span class="emphasis"><i +class="EMPHASIS">Client</i></span>: I need an IP address.<br /> + <span class="emphasis"><i +class="EMPHASIS">Server</i></span>: You may take 192.168.10.10 for 19200 seconds.<br /> + + <span class="emphasis"><i +class="EMPHASIS">Client</i></span>: Thank you.</p> + +<p class="LITERALLAYOUT"> <span class="emphasis"><i +class="EMPHASIS">Client</i></span>: Is there a DHCP server available on the LAN?<br /> + + <span class="emphasis"><i +class="EMPHASIS">Server</i></span>:Yes, there is. Here I am.<br /> + + <span class="emphasis"><i +class="EMPHASIS">Client</i></span>:I need an IP address. The last time we<br /> + + talked, I had 192.168.10.10;<br /> + May I have it again?<br /> + <span class="emphasis"><i +class="EMPHASIS">Server</i></span>:Yes, you may (or No, you may not: take 192.168.10.12 instead).<br /> + + <span class="emphasis"><i +class="EMPHASIS">Client</i></span>: Thank you.</p> + +<p>The DHCP client in Linux is <tt class="COMMAND">/sbin/dhcpcd</tt>. If you load <tt +class="FILENAME">/etc/rc.d/rc.inet1</tt> in your favorite text editor, you will notice +that <tt class="COMMAND">/sbin/dhcpcd</tt> is called about midway through the script. +This will force the conversation shown above. <tt class="COMMAND">dhcpcd</tt> will also +track the amount of time left on the lease for the current IP address, and will +automatically contact the DHCP server with a request to renew the lease when necessary. +DHCP can also control related information, such as what ntp server to use, what route to +take, etc.</p> + +<p>Setting up DHCP on Slackware is simple. Just run <tt class="COMMAND">netconfig</tt> +and select DHCP when offered. If you have more than one NIC and do not wish <tt +class="FILENAME">eth0</tt> to be configured by DHCP, just edit the <tt +class="FILENAME">/etc/rc.d/rc.inet1.conf</tt> file and change the related variable for +your NIC to “<var class="LITERAL">YES</var>”.</p> +</div> + +<div class="SECT2"> +<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-TCPIP-STATIC" +name="NETWORK-CONFIGURATION-TCPIP-STATIC">5.3.2 Static IP</a></h2> + +<p>Static IP addresses are fixed addresses that only change if manually told to. These +are used in any case where an administrator doesn't want the IP information to change, +such for internal servers on a LAN, any server connected to the Internet, and networked +routers. With static IP addressing, you assign an address and leave it at that. Other +machines know that you are always at that certain IP address and can contact you at that +address always.</p> +</div> + +<div class="SECT2"> +<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-TCPIP-CONF" +name="NETWORK-CONFIGURATION-TCPIP-CONF">5.3.3 <tt +class="FILENAME">/etc/rc.d/rc.inet1.conf</tt></a></h2> + +<p>If you plan on assigning an IP address to your new Slackware box, you may do so either +through the <tt class="FILENAME">netconfig</tt> script, or you may edit <tt +class="FILENAME">/etc/rc.d/rc.inet1.conf</tt>. In <tt +class="FILENAME">/etc/rc.d/rc.inet1.conf</tt> , you will notice:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="PROGRAMLISTING"> + # Primary network interface card (eth0) + IPADDR[0]="" + NETMASK[0]="" + USE_DHCP[0]="" + DHCP_HOSTNAME[0]="" +</pre> +</td> +</tr> +</table> + +<p>Then further at the bottom:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="PROGRAMLISTING"> + GATEWAY="" +</pre> +</td> +</tr> +</table> + +<p>In this case, our task is merely to place the correct information between the +double-quotes. These variables are called by <tt class="FILENAME">/etc/rc.d/rc.inet1</tt> +at boot time to setup the nics. For each NIC, just enter the correct IP information, or +put “<var class="LITERAL">YES</var>” for <var class="LITERAL">USE_DHCP</var>. +Slackware will startup the interfaces with the information placed here in the order they +are found.</p> + +<p>The <var class="LITERAL">DEFAULT_GW</var> variable sets up the default route for +Slackware. All communications between your computer and other computers on the Internet +must pass through that gateway if no other route is specified for them. If you are using +DHCP, you will usually not need to enter anything here, as the DHCP server will specify +what gateway to use.</p> +</div> + +<div class="SECT2"> +<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-TCPIP-RESOLVER" +name="NETWORK-CONFIGURATION-TCPIP-RESOLVER">5.3.4 <tt +class="FILENAME">/etc/resolv.conf</tt></a></h2> + +<p>Ok, so you've got an IP address, you've got a default gateway, you may even have ten +million dollars (give us some), but what good is that if you can't resolve names to IP +addresses? No one wants to type in <tt class="HOSTID">72.9.234.112</tt> into their web +browser to reach <tt class="HOSTID">www.slackbook.org</tt>. After all, who other than the +authors would memorize that IP address? We need to setup DNS, but how? That's where <tt +class="FILENAME">/etc/resolv.conf</tt> comes into play.</p> + +<p>Chances are you already have the proper options in <tt +class="FILENAME">/etc/resolv.conf</tt>. If you setup your network connection using DHCP, +the DHCP server should handle updating this file for you. (Technically the DHCP server +just tells <tt class="COMMAND">dhcpcd</tt> what to put here, and it obeys.) If you need +to manually update your DNS server list though, you'll need to hand edit <tt +class="FILENAME">/etc/resolv.conf</tt>. Below is an example:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cat /etc/resolv.conf</kbd> +nameserver 192.168.1.254 +search lizella.net +</pre> +</td> +</tr> +</table> + +<p>The first line is simple. The nameserver directive tells us what DNS servers to query. +By necessity these are always IP addresses. You may have as many listed there as you +like. Slackware will happily check one after the other until one returns a match.</p> + +<p>The second line is a little more interesting. The search directive gives us a list of +domain names to assume whenever a DNS request is made. This allows you to contact a +machine by only the first part of its FQDN (Fully Qualified Domain Name). For example, if +“slackware.com” were in your search path, you could reach <tt +class="HOSTID">http://store.slackware.com</tt> by just pointing your web browser at <tt +class="HOSTID">http://store</tt>.</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">ping -c 1 store</kbd> +PING store.slackware.com (69.50.233.153): 56 data bytes +64 bytes from 69.50.233.153 : icmp_seq=0 ttl=64 time=0.251 ms +1 packets transmitted, 1 packets received, 0% packet loss +round-trip min/avg/max = 0.251/0.251/0.251 ms +</pre> +</td> +</tr> +</table> + +<br /> +<br /> +</div> + +<div class="SECT2"> +<h2 class="SECT2"><a id="NETWORK-CONFIGURATION-TCPIP-HOSTS" +name="NETWORK-CONFIGURATION-TCPIP-HOSTS">5.3.5 <tt +class="FILENAME">/etc/hosts</tt></a></h2> + +<p>Now that we've got DNS working fine, what if we want to bypass our DNS server, or add +a DNS entry for a machine that isn't in DNS? Slackware includes the oft-loved <tt +class="FILENAME">/etc/hosts</tt> file which contains a local list of DNS names and IP +addresses they should match to.</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cat /etc/hosts</kbd> +127.0.0.1 localhost locahost.localdomain +192.168.1.101 redtail +172.14.66.32 foobar.slackware.com +</pre> +</td> +</tr> +</table> + +<p>Here you can see that localhost has an IP address of <tt class="HOSTID">127.0.0.1</tt> +(always reserved for localhost), redtail can be reached at <tt +class="HOSTID">192.168.1.101</tt>, and <tt class="HOSTID">foobar.slackware.com</tt> is +<tt class="HOSTID">172.14.66.32</tt>.</p> +</div> +</div> + +<div class="NAVFOOTER"> +<hr align="LEFT" width="100%" /> +<table summary="Footer navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<td width="33%" align="left" valign="top"><a href="network-configuration-hardware.html" +accesskey="P">Prev</a></td> +<td width="34%" align="center" valign="top"><a href="index.html" +accesskey="H">Home</a></td> +<td width="33%" align="right" valign="top"><a href="network-configuration-ppp.html" +accesskey="N">Next</a></td> +</tr> + +<tr> +<td width="33%" align="left" valign="top">Network Hardware Configuration</td> +<td width="34%" align="center" valign="top"><a href="network-configuration.html" +accesskey="U">Up</a></td> +<td width="33%" align="right" valign="top">PPP</td> +</tr> +</table> +</div> +</body> +</html> + |