DHCP Server (using Windows recommended)

Some small services windows do better than Linux

DHCP Service Overview:

name : DHCP (Dynamic Host Configuration Protocol-Dynamically hosted Config protocol)

function : is a LAN protocol that dynamically assigns IP addresses to clients within the LAN

It has two uses--->

1. Automatically assign an IP address, hostname, DNS server, domain name to the internal network or network service provider

2. Cooperate with other services to realize integrated management function. Such as: Unattended Installation Server

Features: C/S mode

Automatically assign IP addresses for easy management

DHCP does not lease the same IP address to two hosts at the same time (avoid IP collisions)

A DHCP administrator can constrain a specific computer to use a specific IP address (the assigned IP pool is specified)

You can set many options for each DHCP scope (bind IP address)

When a client moves between different subnets, it does not need to reset the IP address. Every time you get an IP address automatically.

Disadvantages:

When there are more than one DHCP server in the network, a DHCP server, do not know the other server leased out IP address (may cause IP conflicts);

The DHCP server cannot communicate with clients across servers unless the router allows BOOTP protocol forwarding.

DHCP Service port: Default Listener 67 68 port

Vim/etc/services

Operating principle: (often asked, interview) (Below is my own understanding of the description)

DHCP Client---> DHCP clients

DHCP server---> DHCP servers

Request assignment IP procedure:

1. DHCP Client--discover--> DHCP Server

After the DHCP client is started, a broadcast of the Discover packet is sent to look for the DHCP Server.

2. DHCP Server--offer--> DHCP Client

When the Discover packet is received by DHCP server, a delivery packet is sent to the DHCP client, which informs the DHCP client that it has received his request that the offerpackage contains (an IP address and other information that has not been used).

3. DHCP Client--request--> DHCP Server

When the DHCP client receives a DHCP server reply packet, it sends a request packet broadcast again, which contains the first message sent by the DHCP server. Means to inform all DHCP servers, He has used the IP information assigned by a DHCP server.

4. DHCP Server--ack--> DHCP Client

When DHCP server receives a request packet sent by a DHCP client, it sends a confirmation message to the DHCP client that it can use the IP address. Other DHCP servers reclaim the IP address information that is assigned to it.

DHCP client logs back on to the network:

1. DHCP Client--request--> DHCP Server

When the DHCP client logs back on to the network, the last DHCP server server is sent a request for the IP address that was originally used.

2. DHCP Server--ack--> DHCP Client

After DHCP server determines that the address has not been allocated, a confirmation message is sent to the DHCP client confirming that it can continue to use the address.

If the DHCP server determines that the address has been used by another client, it will reply that it cannot use this address, which is the DHCP client will send the discovery broadcast again to obtain the IP address.

Request IP Renewal Process:

1. DHCP Client--request--> DHCP Server

The IP information obtained by the DHCP client has a lease.

When the IP address of the DHCP client expires in half the time, the DHCP server server is again sent a renewal request renew.

2. DHCP Server--ack--> DHCP Client

After the DHCP server receives a renewal request, it confirms that it can continue to be used, and then resumes the reply package and renews the DHCP client.

DHCP Server (using Windows recommended)