DHCP services in a detailed

1. DHCP Concepts and principles
   2. DHCP service role
      1. Automatically assign addresses to a large number of clients, providing centralized management
      2. Reduce management and maintenance costs and improve network configuration efficiency
   4. The address information that can be assigned mainly includes:
      1. IP address, subnet mask of the network card
      2. The corresponding network address
      3. Default gateway Address
      4. DNS server address
      5. Boot file, TFTP server address

   5. the principle of DHCP
      2. Clients looking for servers

         Client–dhcpdiscovery

         If not, 9 seconds, 13 seconds, 16 seconds after 1 seconds of re-sending.

      4. Server provides address

         Server–dhcpoffer

         Provide available IP, lease information, server address, etc.

      6. Accept and broadcast

         Client–dhcprequest

         Declare the DHCP server of your choice

         ARP broadcast, testing the DHCP server of your choice

      8. Server Acknowledgement

         Client–dhcprequest

         Server–dhcpack

         All network parameters are included.

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1. Log back in with the client

   Client–dhcprequest

   Application, continue source use assigned IP address

2. Update lease

   8 Hours – 4 hours – 2 hours

   Client–dhcpdiscovery

1. DHCP-related files
   1. rhel6 DHCP package

      dhcp-4.1.1-3.4.p1.el6.x86_64.rpm

   2. DHCP Related configuration

      port number: IPv4 udp67, udp68

      IPv6 udp546, udp547

      service Name: DHCPD (main program) or Dhcrelay (relay)

      Master profile:/etc/dhcp/dhcpd.conf

      P style= "text-align:justify" > template file:/USR/SHARE/DOC/DHCP-4.1.1/ Dhcpd.conf.sample

      trunk configuration file :/etc/sysconfig/dhcrelay

3. DHCP configuration file resolution.

Option Domain-name "example.org";

Option Domain-name-servers ns1.example.org, ns2.example.org;

Default-lease-time 600;

Max-lease-time 7200;

#ddns-update-style None;

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;

}

Host Passacaglia {

Hardware Ethernet 0:0:c0:5d:bd:95;

FileName "Vmunix.passacaglia";

Server-name "toccata.fugue.com";

}

Host Fantasia {

Hardware Ethernet 08:00:07:26:C0:A5;

Fixed-address fantasia.fugue.com;

}

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;

}

}

Option Domain-name setting the DNS domain

Option Domain-name-server Setting the DNS server address

Default-lease-time Set default lease time in seconds

Max-lease-time Setting the maximum lease time in seconds

Log-facility Specifying a log device

Ddns-update-style To configure how DNS is updated

Subnet network Segment declaration, acting on the entire subnet segment:

Range sets the pool of IP addresses for allocation

Option Subnet-mask to set the subnet mask for the client

The option routers parameter sets the client's default gateway address

Option Broadcast-address Setting the client broadcast address

The host hosts a declaration that acts on a host computer:

Hardware Ethernet Set the destination host's MAC address

Fixed-address set to its assigned reserved IP

Restart the service for the modified configuration to take effect

#server dhcpd Restart

Modify the NIC configuration to set up automatic DHCP assignment

#vim/etc/sysconfig/network-scripts/ifcfg-eth0

Device=eth0

Onboot=yes

Bootproto=dhcp

#ifdown eth0

#ifup eth0

Note: After the configuration is complete, remember to close the SELinux and firewall

2. DHCP server-side configuration
4. DHCP Client Configuration
5. case: DHCP relay functionality

   Host A has an IP address of 192.168.1.1, and the gateway is 192.168.1.2

   Host B's IP address is eth0:192.168.1.2,eth1:200.200.200.2

   Host C network adapter set to DHCP

   1, host a operation steps are as follows:

   #yum –y Install DHCP

   #cp???? /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample/etc/dhcp/dhcpd.conf

   #vim/etc/dhcp/dhcpd.conf

   #service DHCPD Start

   #vim/etc/sysctl.conf

   #打开网络转发功能

   1. Host B steps as follows:

      #yum –y Install DHCP

      #vim/etc/sysconfig/dhcrelay

      #service Dhcrelay Start

   2. Host C operates as follows:

      #vim/etc/sysconfig/network-scripts/ifcfg-eth0

#设置为DHCP

1. DHCP host address reserved

   Host A's IP address is 192.168.1.1

   Host B NIC is set to DHCP

   Host A and Host B are in the same network segment

   1, the operating procedure of host A is as follows:

   #yum –y Install DHCP

#cp/usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample

#vim/etc/dhcp/dhcpd.conf

Bind MAC Address

#service dhcpd Restart

2, the operation of Host B is as follows:

#vim/etc/sysconfig/network-scripts/ifcfg-eth0

1. DHCP Hyper-scope

   Description: A superscope is a management feature in a DHCP service that uses a superscope to combine multiple scopes into a single administrative entity.

Test Preparation: Host a network card eth0 and Host B network card eth0 in the same network segment, Host C network card eth1 and Host B network card eth1 in the same network segment , hosts A, B, and C Turn off firewalls and selinux.

1. The operation of Host B is as follows:

   #vim/etc/sysconfig/network-scripts/ifcfg-eth0

#vim/etc/sysconfig/network-scripts/ifcfg-eth1

#yum –y Install DHCP

#cp/usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample/etc/dhcp/dhcpd.conf

#vim/etc/dhcp/dhcpd.conf

#service DHCPD Start

2. Host A's network card settings

   #vim/etc/sysconfig/network-scripts/ Ifcfg-eth0

   #ifdown eth0

   #ifup eth0

   results such as

4. Network card settings for Host C

   #ifdown eth0

   #ifup eth0

   Results

   Summary: using the method above, in two network segments assigned IP address, do not need to do DHCP relay, the only problem is to connect two network segments of the host to have enough network card, that is, a network card corresponding to a segment

DHCP services in a detailed