Comparison between DHCP in Linux and NTServer4.0

Comparison between Linux and DHCP in NTServer4.0-Linux Enterprise Application-Linux server application information. For details, refer to the following section. The BOOTP protocol evolved from the same TCP/IP protocol family. It is a protocol that uses many automatic client TCP/IP configurations on Ethernet. As a widely used network operating system, both NT Server 4.0 and Linux provide DHCP support, this article takes the DHCP Server that comes with NT Server 4.0 and the most common dhcpd 2.0 in Linux as an example to analyze the use and difference of DHCP in the two systems.

I. How DHCP works

Each TCP/IP-based network Host requires a unique 32-bit IP address to communicate with the network. If the IP address of each Host is set manually, the workload will be unimaginable. Can you enable the host to be automatically configured with an IP address at startup to work properly? This is the original intention of DHCP protocol design. When a host with DHCP configured is started, a limited IP address broadcast will be forcibly sent (the 32-bit IP address with full value of 1, namely 255.255.255.255, is called a limited broadcast address, the broadcast of this address is called a finite address broadcast or a local network broadcast ). When the DHCP server in the local network receives the broadcast, it searches for the corresponding configuration on the server based on the received Physical Address (Physical Address, and send an IP address and additional options (such as the lease expiration time) from the IP address pool to the client. Due to the use of broadcast, DHCP without transit obviously cannot span the subnet, in addition, the information of a client may be responded by several servers, so the client always answers the DHCP response received first. After receiving the response, the client also sends a registration message, to tell the server that the IP address has been rented to prevent IP address conflict. The entire registration process is actually a very complex set of procedures. Both parties must exchange information multiple times before the registration can be successful.

Ii. NT: Graphical DHCP Management

NT has always been known for its good operation interface, and DHCP Server is no exception. Through the graphical DHCP manager, you can intuitively obtain the current IP usage of DHCP clients, you can easily modify the configuration of the entire service project and client. Nt dhcp servers support a considerable number of DHCP options, but Windows clients (including NT itself) only a few options are supported, such as IP address, subnet mask, default gateway, DNS server name, domain name, WINS server name, WINS node type, and lease period, however, this covers most configurations in the LAN.

The nt dhcp server defines one or more IP address ranges to provide available IP addresses, subnet masks, and default gateways for the client. However, there can only be one IP address range in a sub-network. Then, you can use the DHCP option to provide more additional settings for the client. The additional settings of NT are the same as those of RFC1541, for example, 006 is the DNS server name and 044 is the WINS server name. If a DHCP Client rents an IP address, additional options will also be passed to it, provided that the client does not configure these additional options, because the local configuration always takes precedence.

If you want to assign a specific IP address to a host instead of Automatically Selecting it, you can add a reserved location and enter the 48-bit physical address of the host's ethernet card as the unique identifier, you can also configure specific hosts. Each time a client with this physical address is logged on, the server will give it a fixed IP address and option.

The advantage of the NT 4.0 DHCP server is that the operation is intuitive, simple, and easy to manage, in addition, it is interesting that Windows clients always give priority to the DHCP service of NT (it seems that there is a conflict with the previous attempt to answer the first response, but as it turns out, in a subnet composed of all Windows hosts, if an nt dhcp server exists, the Linux DHCP server will hardly be used ). Its main drawback is that it cannot effectively control the IP address rented by unknown users. That is to say, as long as there are unused addresses, any requests received will be accepted, in addition, it is complicated to configure multiple clients separately.

3. Linux: giving you more "freedom"

Linux, as a representative of free software, has incomparable advantages in the Windows series. Dhcpd is a DHCP server software that complies with GPL rules. Currently, the latest version is 3.0.1, but most of Linux comes with versions 2.0 and earlier. This document takes a lower version as an example.