1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Content</title>
<base target="_self">
</head>
<body background="../../images/bg.gif" topmargin="0" leftmargin="0" marginheight="0" marginwidth="0" onLoad="window.focus();" link="#808080" vlink="#808080" alink="#808080">
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td bgcolor="#336666" width="18" valign="top">
<img border="0" src="../../images/content_lines.gif" width="16" height="25">
<img border="0" src="../../images/transdot.gif" width="2" height="1"></td>
<td bgcolor="#336666"><font face="Arial" size="2" color="#FFFFFF"><b>1.2</font></b></td>
<td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
<td bgcolor="#336666" width="100%"><b>
<font face="Arial" size="2" color="#FFFFFF">DHCP</font></b></td>
<td width="9" bgcolor="#336666"> </td>
</tr>
<tr>
<td bgcolor="#669999" height="25" width="18"> </td>
<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">1.2.1</font></b></td>
<td bgcolor="#669999"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
<td bgcolor="#669999" height="25" width="100%"><b>
<font face="Arial" size="2" color="#FFFFFF">Introducing DHCP</font></b></td>
<td bgcolor="#669999" height="25" width="9"> </td>
</tr></table>
<table border="0" cellpadding="0" cellspacing="0" width="95%" bordercolor="#111111">
<tr>
<td width="15"></td>
<td>
<font face="Arial" size="2">Dynamic Host Configuration Protocol (DHCP)
works in a client/server mode. DHCP enables DHCP clients on an IP
network to obtain their configurations from a DHCP server. Less work
is involved in managing an IP network when DHCP is used. The
most significant configuration option the client receives from the
server is its IP address. The DHCP protocol is described in RFC 2131.</font><p>
<font face="Arial" size="2">A DHCP client is included in most modern
operating systems including the various Windows operating systems,
Novell Netware, Sun Solaris, Linux, and MAC OS. The client requests
addressing values from the network DHCP server.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> This
server manages the allocation of the IP addresses and will answer
configuration requests from clients.
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12">
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"> The DHCP
server can answer requests for many subnets. DHCP is not intended for
configuring routers, switches, and servers. These type of hosts all
need to have static IP addresses.</font></p>
<p>
<font face="Arial" size="2">DHCP works by providing a process for a
server to allocate IP information to clients. Clients lease the
information from the server for an administratively defined period.
When the lease expires the client must ask for another address,
although the client is typically reassigned the same address.</font></p>
<p>
<font face="Arial" size="2">Administrators typically prefer a network
server to offer DHCP services because these solutions are scalable and
relatively easy to manage. Cisco routers can use a Cisco IOS feature
set, Easy IP, to offer an optional, full-featured DHCP server. Easy IP leases configurations for 24 hours by default.
This is useful in small offices and home offices where the home user
can take advantage of DHCP and NAT without having an NT or UNIX
server. </font>
</p>
<p>
<font face="Arial" size="2">Administrators set up DHCP servers to
assign addresses from predefined pools. DHCP servers can also offer
other information, such as DNS server addresses, WINS server
addresses, and domain names. Most DHCP servers also allow the
administrator to define specifically what client MAC addresses can be
serviced and automatically assign them the same IP address each time.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12">
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12">
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></font></p>
<p>
<font face="Arial" size="2">DHCP uses UDP as its transport protocol.
The client sends messages to the server on port 67. The server sends
messages to the client on port 68.</font></p>
<p>
<TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top">
<TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
<TR>
<TD width="5">
<img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
<TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
<IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
</TR>
</TABLE>
<TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
<TR>
<TD>
<TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
<TR>
<TD bgcolor="#ffffff" width="15"> </TD>
<TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
<p><font color="#808080">
<img border="0" src="../../images/links_icon.gif" width="25" height="25">
<b>Web Links</b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>DHCP Overview<p>
<a target="_blank" href="http://support.baynetworks.com/library/tpubs/html/router/soft1200/117362AA/A_29.HTM">
http://support.baynetworks.com/library/
tpubs/html/ router/soft1200/ 117362AA/A_29.HTM</a></font></p>
<p>
<IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE><p>
</td>
</tr>
</table>
</body>
</html>
|
