Linux系統上DHCP伺服器的配置 .
Linux系統上DHCP伺服器的配置 .
一、DHCP的工作流程
(1) DHCP伺服器發現階段。DHCP客戶機向廣播地址255.255.255.255發送DHCPDiscover消息。
(2) DHCP伺服器響應階段。DHCP伺服器從尚未出租的IP地址池中選擇一個分配給DHCP客戶機，向DHCP客戶機發送一個包含出租的IP地址和其他設置的DHCPoffer提供信息。
(3) IP地址選擇階段。DHCP客戶機選擇某個DHCP伺服器提供的IP地址，以廣播方式回答一個DHCPrequest請求信息.
(4) IP地址確認階段。伺服器回應包含它所提供的IP地址和其他設置的DHCPack確認信息。然後客戶機將其與TCP/IP協議與網卡綁定。
(5) 客戶機重新登錄。再次發送前次分配的IP地址的DHCPRequest請求請求信息，DHCP伺服器檢查是否可以繼續讓客戶機使用，然後發回DHCPack確認信息或者DHCPnck否認信息。如果IP已不能用，客戶機需從(1)開始重新申請。
(6) 更新租約。IP地址租借期限到了，如果DHCP客戶機要延長其租約，必須更新。DHCP客戶機啟動時和IP租約期限過一半時，都會向伺服器發送更新期IP租約的信息。
二、DHCP伺服器配置文件
路徑在/etc/dhcp/dhcpd.conf。下面是一個配置文件的例子：view plaincopy to clipboardprint?
01.
# dhcpd.conf
02.#
03.# Sample configuration file for ISC dhcpd
04.#
05.
06.# option definitions common to all supported networks...
07.option domain-name "example.org";
08.option domain-name-servers ns1.example.org, ns2.example.org;
09.
10.default-lease-time 600;
11.max-lease-time 7200;
12.
13.# Use this to enble / disable dynamic dns updates globally.
14.#ddns-update-style none;
15.
16.# If this DHCP server is the official DHCP server for the local
17.# network, the authoritative directive should be uncommented.
18.#authoritative;
19.
20.# Use this to send dhcp log messages to a different log file (you also
21.# have to hack syslog.conf to complete the redirection).
22.log-facility local7;
23.
24.# No service will be given on this subnet, but declaring it helps the
25.# DHCP server to understand the network topology.
26.
27.subnet 10.152.187.0 netmask 255.255.255.0 {
28.}
29.
30.# This is a very basic subnet declaration.
31.
32.subnet 10.254.239.0 netmask 255.255.255.224 {
33. range 10.254.239.10 10.254.239.20;
34. option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
35.}
36.
37.# This declaration allows BOOTP clients to get dynamic addresses,
38.# which we don't really recommend.
39.
40.subnet 10.254.239.32 netmask 255.255.255.224 {
41. range dynamic-bootp 10.254.239.40 10.254.239.60;
42. option broadcast-address 10.254.239.31;
43. option routers rtr-239-32-1.example.org;
44.}
45.
46.# A slightly different configuration for an internal subnet.
47.subnet 10.5.5.0 netmask 255.255.255.224 {
48. range 10.5.5.26 10.5.5.30;
49. option domain-name-servers ns1.internal.example.org;
50. option domain-name "internal.example.org";
51. option routers 10.5.5.1;
52. option broadcast-address 10.5.5.31;
53. default-lease-time 600;
54. max-lease-time 7200;
55.}
56.
57.# Hosts which require special configuration options can be listed in
58.# host statements. If no address is specified, the address will be
59.# allocated dynamically (if possible), but the host-specific information
60.# will still come from the host declaration.
61.
62.host passacaglia {
63. hardware ethernet 0:0:c0:5d:bd:95;
64. filename "vmunix.passacaglia";
65. server-name "toccata.fugue.com";
66.}
67.
68.# Fixed IP addresses can also be specified for hosts. These addresses
69.# should not also be listed as being available for dynamic assignment.
70.# Hosts for which fixed IP addresses have been specified can boot using
71.# BOOTP or DHCP. Hosts for which no fixed address is specified can only
72.# be booted with DHCP, unless there is an address range on the subnet
73.# to which a BOOTP client is connected which has the dynamic-bootp flag
74.# set.
75.host fantasia {
76. hardware ethernet 08:00:07:26:c0:a5;
77. fixed-address fantasia.fugue.com;
78.}
79.
80.# You can declare a class of clients and then do address allocation
81.# based on that. The example below shows a case where all clients
82.# in a certain class get addresses on the 10.17.224/24 subnet, and all
83.# other clients get addresses on the 10.0.29/24 subnet.
84.
85.class "foo" {
86. match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
87.}
88.
89.shared-network 224-29 {
90. subnet 10.17.224.0 netmask 255.255.255.0 {
91. option routers rtr-224.example.org;
92. }
93. subnet 10.0.29.0 netmask 255.255.255.0 {
94. option routers rtr-29.example.org;
95. }
96. pool {
97. allow members of "foo";
98. range 10.17.224.10 10.17.224.250;
99. }
100. pool {
101. deny members of "foo";
102. range 10.0.29.10 10.0.29.230;
103. }
104.}
105. # dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#
# option definitions common to all supported networks...
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;
default-lease-time 600;
max-lease-time 7200;
# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;
# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;
# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;
# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.
subnet 10.152.187.0 netmask 255.255.255.0 {
}
# This is a very basic subnet declaration.
subnet 10.254.239.0 netmask 255.255.255.224 {
range 10.254.239.10 10.254.239.20;
option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}
# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.
subnet 10.254.239.32 netmask 255.255.255.224 {
range dynamic-bootp 10.254.239.40 10.254.239.60;
option broadcast-address 10.254.239.31;
option routers rtr-239-32-1.example.org;
}
# A slightly different configuration for an internal subnet.
subnet 10.5.5.0 netmask 255.255.255.224 {
range 10.5.5.26 10.5.5.30;
option domain-name-servers ns1.internal.example.org;
option domain-name "internal.example.org";
option routers 10.5.5.1;
option broadcast-address 10.5.5.31;
default-lease-time 600;
max-lease-time 7200;
}
# Hosts which require special configuration options can be listed in
# host statements. If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.
host passacaglia {
hardware ethernet 0:0:c0:5d:bd:95;
filename "vmunix.passacaglia";
server-name "toccata.fugue.com";
}
# Fixed IP addresses can also be specified for hosts. These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP. Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
host fantasia {
hardware ethernet 08:00:07:26:c0:a5;
fixed-address fantasia.fugue.com;
}
# You can declare a class of clients and then do address allocation
# based on that. The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.
class "foo" {
match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}
shared-network 224-29 {
subnet 10.17.224.0 netmask 255.255.255.0 {
option routers rtr-224.example.org;
}
subnet 10.0.29.0 netmask 255.255.255.0 {
option routers rtr-29.example.org;
}
pool {
allow members of "foo";
range 10.17.224.10 10.17.224.250;
}
pool {
deny members of "foo";
range 10.0.29.10 10.0.29.230;
}
}
DHCP配置文件通常包括3部分：declarations, parameters, options。
declarations：描述網路的布局；描述客戶；提供客戶的地址。
parameters：表明如何執行任務，是否要執行任務，或將哪些網路配置選項發送給客戶。
option：配置DHCP可選參數。
常用聲明：
shared-network 告知DHCP伺服器是否為一些子網路分享相同網路
subnet 描述一個IP是否屬於子網
range 提供動態分配IP地址的起始和結束範圍
host 為特定的主機提供網路參數
group 為一組參數提供聲明
常用參數：
ddns-update-style 配置DHCP-DNS互動更新模式
default-lease-time 指定默認租賃時間的長度，單位為秒
max-lease-time 指定最大租賃時間長度，單位為秒
hardware 指定網卡介面類型和MAC地址
server-name 告知DHCP客戶伺服器名稱
fixed-address 為客戶端指定一個固定的IP地址
常用選項：
domain-name 為客戶端指定域名
domain-name-servers為客戶端指明DNS伺服器IP地址
host-name 為客戶端指明主機名稱
routers 為客戶端指明默認網關
broadcast-address 為客戶端設定廣播地址
subnet-mask 為客戶端設定子網掩碼
ntp-server 為客戶端設定格林威治時間的偏移時間，單位為秒
下面是一個DHCPv6的配置文件的例子：view plaincopy to clipboardprint?
01.# Server configuration file example for DHCPv6
02.# From the file used for TAHI tests.
03.
04.# IPv6 address valid lifetime
05.# (at the end the address is no longer usable by the client)
06.# (set to 30 days, the usual IPv6 default)
07.default-lease-time 2592000;
08.
09.# IPv6 address preferred lifetime
10.# (at the end the address is deprecated, i.e., the client should use
11.# other addresses for new connections)
12.# (set to 7 days, the usual IPv6 default)
13.preferred-lifetime 604800;
14.
15.# T1, the delay before Renew
16.# (default is 1/2 preferred lifetime)
17.# (set to 1 hour)
18.option dhcp-renewal-time 3600;
19.
20.# T2, the delay before Rebind (if Renews failed)
21.# (default is 3/4 preferred lifetime)
22.# (set to 2 hours)
23.option dhcp-rebinding-time 7200;
24.
25.# Enable RFC 5007 support (same than for DHCPv4)
26.allow leasequery;
27.
28.# Global definitions for name server address(es) and domain search list
29.option dhcp6.name-servers 3ffe:501:ffff:100:200:ff:fe00:3f3e;
30.option dhcp6.domain-search "test.example.com","example.com";
31.
32.# Set preference to 255 (maximum) in order to avoid waiting for
33.# additional servers when there is only one
34.##option dhcp6.preference 255;
35.
36.# Server side command to enable rapid-commit (2 packet exchange)
37.##option dhcp6.rapid-commit;
38.
39.# The delay before information-request refresh
40.# (minimum is 10 minutes, maximum one day, default is to not refresh)
41.# (set to 6 hours)
42.option dhcp6.info-refresh-time 21600;
43.
44.# The path of the lease file
45.dhcpv6-lease-file-name "/usr/local/var/db/dhcpd6.leases";
46.
47.# Static definition (must be global)
48.host myclient {
49. # The entry is looked up by this
50. host-identifier option
51. dhcp6.client-id 00:01:00:01:00:04:93:e0:00:00:00:00:a2:a2;
52.
53. # A fixed address
54. fixed-address6 3ffe:501:ffff:100::1234;
55.
56. # A fixed prefix
57. fixed-prefix6 3ffe:501:ffff:101::/64;
58.
59. # Override of the global definitions,
60. # works only when a resource (address or prefix) is assigned
61. option dhcp6.name-servers 3ffe:501:ffff:100:200:ff:fe00:4f4e;
62.
63. # For debug (to see when the entry statements are executed)
64. # (log "sol" when a matching Solicitation is received)
65. ##if packet(0,1) = 1 { log(debug,"sol"); }
66.}
67.
68.# The subnet where the server is attached
69.# (i.e., the server has an address in this subnet)
70.subnet6 3ffe:501:ffff:100::/64 {
71. # Two addresses available to clients
72. # (the third client should get NoAddrsAvail)
73. range6 3ffe:501:ffff:100::10 3ffe:501:ffff:100::11;
74.
75. # Use the whole /64 prefix for temporary addresses
76. # (i.e., direct application of RFC 4941)
77. range6 3ffe:501:ffff:100:: temporary;
78.
79. # Some /64 prefixes available for Prefix Delegation (RFC 3633)
80. prefix6 3ffe:501:ffff:100:: 3ffe:501:ffff:111:: /64;
81.}
82.
83.# A second subnet behind a relay agent
84.subnet6 3ffe:501:ffff:101::/64 {
85. range6 3ffe:501:ffff:101::10 3ffe:501:ffff:101::11;
86.
87. # Override of the global definitions,
88. # works only when a resource (address or prefix) is assigned
89. option dhcp6.name-servers 3ffe:501:ffff:101:200:ff:fe00:3f3e;
90.
91.}
92.
93.# A third subnet behind a relay agent chain
94.subnet6 3ffe:501:ffff:102::/64 {
95. range6 3ffe:501:ffff:102::10 3ffe:501:ffff:102::11;
96.}
《解決方案》
不錯的文章。呵呵。
《解決方案》
http://redking.blog.51cto.com/27212/127548
