DHCP多作用域設定
DHCP伺服器使用單一的作用域，大部分時間能夠滿足網路的需求，但是有些特殊情況下，按照網路規劃我們需要配置多作用域。
網路中如果計算機和其他裝置數量增加，IP地址需要進行擴容才能滿足需求。小型網路可以對所有裝置重新分配IP地址，其網路內部客戶機和伺服器數量較少，實現起來比較簡單。但如果是一個大型網路，重新配置整個網路的IP地址是不明智的，如果操作不當，可能會造成通訊暫時中斷以及其他網路故障。我們可以透過多作用域的設定，即DHCP伺服器釋出多個作用域實現IP地址增容的目的。
公司IP地址規劃為192.168.2.0/24網段，可以容納254臺裝置，使用DHCP伺服器建立一個192.168.2.0網段的作用域，動態管理網路IP地址，但網路規模擴大到500臺機器，顯然一個C類網的地址無法滿足要求了。這時，可以再為DHCP伺服器新增一個新作用域，管理分配192.168.3.0/24網段的IP地址，為網路增加254個新的IP地址，這樣既可以保持原有IP地址的規劃，又可以擴容現有的網路IP地址。
（1）簡單實現DHCP多作用域
對於多作用域的配置，必須保證DHCP伺服器能夠偵聽所有子網客戶機的請求資訊，下面將講解配置多作用域的基本方法，為DHCP新增多個網絡卡連線每個子網，併發布多個作用域的宣告。
注意：劃分子網時，如果選擇直接配置多作用域實現動態IP分配的任務，則必須要為DHCP伺服器新增多塊網絡卡，並配置多個IP地址，否則DHCP伺服器只能分配與其現有網絡卡IP地址對應網段的作用域。
採用雙網絡卡實現兩個作用域
1）網絡卡配置IP地址
DHCP伺服器有多塊網絡卡時，需要使用ifconfig命令為每塊網絡卡配置獨立的IP地址，但要注意，IP地址配置的網段要與DHCP伺服器釋出的作用域對應哈~
ifconfig eth0 192.168.2.1 netmask 255.255.255.0
ifconfig eth1 192.168.3.1 netmask 255.255.255.0
2）編輯dhcpd.conf主配置檔案
當DHCP伺服器網路環境搭建完畢後，我們可以編輯dhcpd.conf主配置檔案完成多作用域的設定。
ddns-update-style none;
ignore client-updates;
subnet 192.168.2.0 netmask 255.255.255.0 {
# --- default gateway
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;
option nis-domain "domain.org";
option domain-name "domain.org";
option domain-name-servers 192.168.2.2;
option time-offset -18000; # Eastern Standard Time
# option ntp-servers 192.168.1.1;
# option netbios-name-servers 192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don"t change this unless
# -- you understand Netbios very well
# option netbios-node-type 2;
range dynamic-bootp 192.168.2.50 192.168.2.250;
default-lease-time 21600;
max-lease-time 43200;
# we want the nameserver to appear at a fixed address
host ns {
next-server marvin.redhat.com;
hardware ethernet 12:34:56:78:AB:CD;
fixed-address 207.175.42.254;
}
subnet 192.168.3.0 netmask 255.255.255.0 {
option routers 192.168.3.1;
range dynamic-bootp 192.168.3.50 192.168.3.250;
儲存退出哈~
3）測試驗證
重啟DHCP服務後檢查系統日誌，檢測配置是否成功，使用tail命令動態顯示日誌資訊。
tail -F /etc/log/messages
經過設定，對於DHCP伺服器將透過eth0和eth1兩塊網絡卡偵聽客戶機的請求，併發送相應的迴應。
Jan 19 16:02:51 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da via eth1
Jan 19 16:02:51 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da via eth0
Jan 19 16:02:52 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:52 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:53 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:53 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:53 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:54 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:54 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:54 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:55 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:55 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:55 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
DHCP多作用域設定
DHCP伺服器使用單一的作用域，大部分時間能夠滿足網路的需求，但是有些特殊情況下，按照網路規劃我們需要配置多作用域。
網路中如果計算機和其他裝置數量增加，IP地址需要進行擴容才能滿足需求。小型網路可以對所有裝置重新分配IP地址，其網路內部客戶機和伺服器數量較少，實現起來比較簡單。但如果是一個大型網路，重新配置整個網路的IP地址是不明智的，如果操作不當，可能會造成通訊暫時中斷以及其他網路故障。我們可以透過多作用域的設定，即DHCP伺服器釋出多個作用域實現IP地址增容的目的。
公司IP地址規劃為192.168.2.0/24網段，可以容納254臺裝置，使用DHCP伺服器建立一個192.168.2.0網段的作用域，動態管理網路IP地址，但網路規模擴大到500臺機器，顯然一個C類網的地址無法滿足要求了。這時，可以再為DHCP伺服器新增一個新作用域，管理分配192.168.3.0/24網段的IP地址，為網路增加254個新的IP地址，這樣既可以保持原有IP地址的規劃，又可以擴容現有的網路IP地址。
（1）簡單實現DHCP多作用域
對於多作用域的配置，必須保證DHCP伺服器能夠偵聽所有子網客戶機的請求資訊，下面將講解配置多作用域的基本方法，為DHCP新增多個網絡卡連線每個子網，併發布多個作用域的宣告。
注意：劃分子網時，如果選擇直接配置多作用域實現動態IP分配的任務，則必須要為DHCP伺服器新增多塊網絡卡，並配置多個IP地址，否則DHCP伺服器只能分配與其現有網絡卡IP地址對應網段的作用域。
採用雙網絡卡實現兩個作用域
1）網絡卡配置IP地址
DHCP伺服器有多塊網絡卡時，需要使用ifconfig命令為每塊網絡卡配置獨立的IP地址，但要注意，IP地址配置的網段要與DHCP伺服器釋出的作用域對應哈~
ifconfig eth0 192.168.2.1 netmask 255.255.255.0
ifconfig eth1 192.168.3.1 netmask 255.255.255.0
2）編輯dhcpd.conf主配置檔案
當DHCP伺服器網路環境搭建完畢後，我們可以編輯dhcpd.conf主配置檔案完成多作用域的設定。
ddns-update-style none;
ignore client-updates;
subnet 192.168.2.0 netmask 255.255.255.0 {
# --- default gateway
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;
option nis-domain "domain.org";
option domain-name "domain.org";
option domain-name-servers 192.168.2.2;
option time-offset -18000; # Eastern Standard Time
# option ntp-servers 192.168.1.1;
# option netbios-name-servers 192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don"t change this unless
# -- you understand Netbios very well
# option netbios-node-type 2;
range dynamic-bootp 192.168.2.50 192.168.2.250;
default-lease-time 21600;
max-lease-time 43200;
# we want the nameserver to appear at a fixed address
host ns {
next-server marvin.redhat.com;
hardware ethernet 12:34:56:78:AB:CD;
fixed-address 207.175.42.254;
}
}
subnet 192.168.3.0 netmask 255.255.255.0 {
# --- default gateway
option routers 192.168.3.1;
option subnet-mask 255.255.255.0;
option nis-domain "domain.org";
option domain-name "domain.org";
option domain-name-servers 192.168.2.2;
option time-offset -18000; # Eastern Standard Time
# option ntp-servers 192.168.1.1;
# option netbios-name-servers 192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don"t change this unless
# -- you understand Netbios very well
# option netbios-node-type 2;
range dynamic-bootp 192.168.3.50 192.168.3.250;
default-lease-time 21600;
max-lease-time 43200;
max-lease-time 43200;
}
儲存退出哈~
3）測試驗證
重啟DHCP服務後檢查系統日誌，檢測配置是否成功，使用tail命令動態顯示日誌資訊。
tail -F /etc/log/messages
經過設定，對於DHCP伺服器將透過eth0和eth1兩塊網絡卡偵聽客戶機的請求，併發送相應的迴應。
Jan 19 16:02:51 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da via eth1
Jan 19 16:02:51 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da via eth0
Jan 19 16:02:52 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:52 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:52 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:53 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:53 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:53 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:53 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:54 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:54 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:54 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:54 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).
Jan 19 16:02:55 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPOFFER . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPDISCOVER from 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:55 rhel5 dhcpd: DHCPOFFER . 192.168.2.250 to 00:19:21:bd:a3:da (mis) via eth0
Jan 19 16:02:55 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPACK . 192.168.3.250 to 00:19:21:bd:a3:da (mis) via eth1
Jan 19 16:02:55 rhel5 dhcpd: DHCPREQUEST for 192.168.3.250 (192.168.3.1) from 00:19:21:bd:a3:da (mis) via eth0: ignored (not authoritative).