Detailed steps for configuring Huawei DHCP

We know that most DHCP server settings can be implemented on routers and switches. Today, we will focus on the Huawei DHCP configuration. First, let's take a look at the basic concept: BOOTP relay proxy BOOTP (Bootstrap Protocol) the relay proxy is an Internet host or router that transmits DHCP messages between the DHCP server and the DHCP client. The BOOTP protocol is designed for remote guidance, DHCP is an extension of the BOOTP mechanism, this feature means that existing BOOTP clients can interact with DHCP servers without changing the software installed. RFC 1542 describes the interaction between BOOTP, DHCP clients, and DHCP servers in detail. the BOOTP relay proxy is the same as the BOOTP protocol, the DHCP protocol also works in client/server mode. With this protocol, the DHCP client can dynamically request configuration information from the DHCP server, including assigned IP addresses, subnet masks, default gateways, and other important parameters, the DHCP server can also easily configure this information dynamically. DHCP provides a solution framework for setting hosts on the TCP/IP network. DHCP inherits from BOOTP, in addition, the function of automatically allocating reusable network addresses and adding configuration options is added. DHCP has a BOOTP relay proxy behavior, DHCP users can interact with BOOTP users. The DHCP Message format is based on the BOOTP Message format, so as to have the behavior of the relay proxy and allow the existing BOOTP client to collaborate with the DHCP server (interoperability ), BOOTP relay proxy avoids the need for a DHCP server in each physical network segment. DHCP defines a mechanism through which, the client can be assigned a network parameter with a certain lease period, and the continuous redistribution of network addresses for different clients is considered. DHCP provides a mechanism, allow the client to obtain all IP configuration parameters for operation. The DHCP principle introduces the network configuration becoming more and more complex as the network scale expands and the network complexity increases, when the computer location changes (such as the Host machine or wireless network) and the number of computers exceeds the assigned IP address, Dynamic Host Configuration Protocol DHCP (Dynamic Host Configuration Protocol) the DHCP protocol works in client/server mode. The DHCP client dynamically requests configuration information from the DHCP server, the DHCP Server returns the corresponding configuration information (such as IP addresses) according to the policy. In typical DHCP applications, the DHCP Server generally contains one DHCP Server and multiple clients (such as PCs and laptops )｡

IP Address Allocation configured by Huawei DHCP

1. IP Address Allocation Policy

Different clients have different requirements for the time occupied by IP addresses: for servers, you may need to use a fixed IP address for a long time; for some hosts, you may need to use a dynamically assigned IP address for a long time; some individuals may only assign a temporary IP address as needed ｡

Manual Address Allocation: The administrator configures a fixed IP address for a few specific clients (such as WWW servers ｡

Automatically assign an address: assign a fixed IP address to some clients that connect to the network for the first time. This address will be used by the client for a long time.

. Dynamic Address Allocation: assign an address to the client by leasing. After the expiration time, the client needs to apply for the address again. Most clients obtain the dynamically allocated address ｡

2. Priority of IP Address Allocation

In the following order, the DHCP server selects an address other than the forbidden-IP address for the client:

. Static IP address bound to the client MAC address in the address pool of the DHCP server;

. The IP address used by the client before, that is, the address of the Request IP address Option (Requested IP Addr Option) in the DHCP_Discover packet sent by the client;

In the DHCP address pool, find the IP addresses available for allocation in sequence, and find the IP addresses first;

If no available IP addresses are found, query the IP addresses that have exceeded the lease term and conflict with each other in sequence. If yes, allocate the IP addresses. Otherwise, an error is reported.

3. DHCP server address pool type

. Global address pool: valid in this switch. It is created through the dhcp server ip-pool command in the System View.

. VLAN interface address pool: valid in this VLAN interface. A valid unicast IP address is configured for the vlan interface, in addition, in the VLAN interface view, use the dhcp select interface command to set the IP address allocated from the vlan interface address pool, and then the system creates the IP address range, which is the network segment of the vlan interface ｡

Huawei DHCP configuration: Interaction Between the DHCP client and the server

To obtain valid Dynamic IP addresses, the DHCP Client interacts with the server in different stages. There are usually three modes:

1. The DHCP client logs on to the network for the first time.

When a DHCP client logs on to the network for the first time, it establishes contact with the DHCP server through four phases ｡

The discovery phase, that is, the phase in which the DHCP client looks for the DHCP server. The client sends the DHCP_Discover packet in broadcast mode, and only the DHCP server responds ｡

The provision phase, that is, the IP address provided by the DHCP server. After receiving the DHCP_Discover packet from the client, the DHCP server selects an unallocated IP address from the IP address pool and assigns it to the client, send the DHCP_Offer packet containing the rental IP address and other settings to the client ｡

Select a stage, that is, the IP address Phase selected by the DHCP client. If Multiple DHCP servers send DHCP_Offer packets to the client, the client only accepts the first DHCP_Offer packet received, then, return the DHCP_Request packet to each DHCP server in broadcast mode, which contains the IP Address requested from the selected DHCP server ｡

The confirmation phase, that is, the phase in which the DHCP server confirms the IP address provided. When the DHCP server receives the DHCP_Request packet from the DHCP client, the client sends the DHCP_ACK validation packet containing the IP address provided by the client and other settings. Then, the DHCP client binds its TCP/IP protocol component to the NIC ｡