Dhcp server configuration management full Raiders

        The role of the DHCP server:
DHCP server Needless to say, without running a DHCP server, IP clients will lose some or all of their ability to access the network. It can be said that the DHCP server is one of the best assistants for enterprise network administrators. With the DHCP server, our network governance work has become more comfortable. However, although the DHCP server is not a new technology, it is not easy to configure and maintain a DHCP server. Especially in some more complex large and medium-sized networks, the deployment of DHCP server networks will involve many more complex technologies. There are many failures encountered by the DHCP server, and various failures and problems are plaguing IT managers. I believe that no matter the fame of the new contact network or the famous technical master, the DHCP server brings more trouble to them. Similar



dhcp protocol functions and protocols:
1 & gt ;. arp action protocol: IP address - & gt; MAC address
2 & gt ;. rarp protocol effect: MAC address--> ip address, dhcp is actually to translate the MAC address into an ip address.
3>. The purpose of the bootp protocol is to respond to the client's single ip address. However, this protocol has no lease. Once an address is assigned to the client, the address will be permanently used by the client. Even if the client is not started, the address will not respond to other clients. Boot protocol This protocol is suitable for the construction of diskless workstations.

dhcp server information in response to customer orders which:
1 & gt; IP /NETMASK
2 & gt; GATEWAY
3 & gt; DNS SERVER
4 & gt; .NTP SERVER

5 & gt; .WINS sERVER

dhcp client requests a complete process:
1 & gt ;. client: dhcp discover (dhcp client broadcasts discovery server)
2 & gt ;. Server: dhcp offer (dhcp server response)
3>. Client: dhcp request (client makes a request)
4>. Server: dhcp ack (server sends response message to client)
Note :
1>. The entire dhcp request process, whether it is the client or the server, sends a message that is broadcast.
2>. The way the client obtains the ip address through dhcp: The client will broadcast the request ip address. If there is a dhcp server in the LAN, it will respond to the ip address to the client.
3>. When there are multiple dhcp servers in the LAN, the client will only accept one of the dhcp servers and reject the others.

dhcp protocol of technical terms:
lease time: the lease period. The valid time for the client to obtain the ip address.
dhcp relay: dhcp relay, dhcp relay is suitable for the network segment to obtain the ip address.

client request process, how to extend the lease:

client lease time in the past half, then request an extension of the lease, the server-side response single client to the server, lease Time becomes the original lease time. When the server does not respond to the client, when the client leases the past half of the lease time, the server sends a request again, requesting to extend the lease time. In this way, when the lease time passes 93.75%, the client will broadcast to the client. discover new dhcp server (dhcp discover)

dhcp server and client-initiated port: port number
server starts: 68 (udp)
client startup port number: achieve 67 (udp)


dhcp service implementation
dhcp function in Linux hosts in two ways:
1 & gt ;. dhcp
dHCP (Dynamic host Configuration Protocol) is a Protocol which allows individual devices on an IP network to get their own network configuration information (IP address, subnetmask, broadcast address, etc.) from a DHCP server.
2>. dnsmasq
Dnsmasq is lightweight, easy to configure DNS forwarder and DHCP server. It is designed to provide DNS and, optionally, DHCP, to a small network. It can serve the names of local machines which are not in the globa DNS.
dnsmasq The job is characterized by lightweight. Simple implementation

centos7.2 dhcp service on the host:

lab topology:


the following steps: building the
node1 dhcp server:
1 & gt ;. [root @ node2 ~] # yum install -y dhcp

2 & gt ;. configuration files and file unit
dhcp profile:
/etc /dhcp /Dhcpd.conf
/etc/dhcp/dhcpd6.conf
dhcp unit file File:
/usr/lib/systemd/system/dhcpd.service
/usr/lib/systemd/system/dhcpd6 .service

3 & gt ;. modify /etc/dhcp/dhcpd.conf profile:
a & gt ;. specified search domain specified DNS address

.. b>. Specify the minimum default lease duration and maximum lease duration.


c & gt ;. designated ip pool.



4 & gt ;. start dhcp service


5 & gt ;. add a default gateway:.

6 & gt ;. Restart the dhcpd service.

node2 Node Test:
1 & gt ;. manual test

2 & gt ;. view generated ip address and gateway information.
ip address
Gateway Address:

node1 node
dhcp server specified by the client host card mac address assigned ip address:
modify the configuration file: Use the host option


restart dhcpd service.

node2 node test:



modify the configuration file are experiencing trouble summarize:
modify the configuration file, There must be a subnet in the subnet where the ip address is located.