the Difference Between Stateful and Stateless DHCP

关键字：IPv6 IPv4 IP DHCP DHCPv6 autoconf IPv6地址 自动分配 自动配置 有状态 无状态 stateful stateless

Well, instead of me just jumping right into explaining the difference between Stateful and Stateless DHCP. I’m going to slow down just a bit and briefly explain DHCP first.

DHCP stands for Dynamic Host Configuration Protocol, this client / server protocol has been around for awhile now, and is regually implemented on IPv4 networks. IPv4 DHCP, is explained in RFC 2131 and IPv6 DHCP is explained in RFC 3315. But, in a nutshell; network adminstrators use DHCP to provide a framework that is used by networked devices (DHCP clients) to obtain various necessary parameters from DHCP Servers so the DHCP clients can operate in an Internet Protocol (IP) network. Now when it comes to DHCP for IPv6 (RFC 3315), there are two ways DHCPv6 can be implemented, either Stateful or Stateless.

Stateful DHCP is centrally managed on a DHCP server(s); and the DHCP clients use Stateful DHCP to obtain an IP address(es) and other useful configuration informaiton from the DHCP server(s).

在介绍有状态和无状态IPv6地址自动配置的区别之前，请允许我先介绍一下DHCP。

DHCP是动态主机配置协议的缩写，这种C/S方式的协议在IPv4网络中已经广泛部署并为大家所认可。IPV4 DHCP是在RFC2131中定义的，IPv6DHCP是在RFC3315中定义的，简单地说，DHCP客户端从DHCP服务端得到IP地址，加入IP网 络，而无需手工干预。当发展到IPv6网络时，就有两种IPv6地址的自动配置的方式：有状态地址自动配置和无状态地址自动配置。

有状态的地址自动配置是指由DHCP服务器统一管理，客户端从DHCP服务器的地址池中拿到IPv6地址和其他信息(例如DNS等)。

But, Stateless DHCP on the other hand; means the DHCP server(s) is not required to store any dynamic state information on the DHCP server(s) about any indivisual DHCP clients. Instead, the DHCP clients autoconfigure their own IP address(es) based on router advertisments. So, with Stateless DHCP, the DHCP clients don’t use the DHCP server(s) to obtain IP address(es) information, they use the DHCP server(s) to obtain the other useful configuration informaiton (like the address(es) of DNS servers).

无状态地址自动配置是指不需要DHCP服务器进行管理，客户端根据网络RA(路由通告)并根据自己的MAC地址计算出自己的IPv6地址。他们一般使用DHCP服务器来获取DNS服务器的地址。

Currently, Cisco recommends that you use Stateless DHCP instead of Stateful DHCP when implementing and deploying IPv6 networks; because, Cisco Routers are not designed to act as Stateful DHCPv6 servers. But, if you need to implement Stateful DHCP on your IPv6 network; Cisco makes a product named Cisco Network Registar (CNR) that can help you out a lot.

I invite you to visit my website were you’ll find the latest information regarding Cisco IPv6 Design and ImplementationTechniques.

一般情况下，Cisco推荐使用无状态地址自动配置，cisco路由器并没有设计DHCPv6服务器。但是如果你需要在网络中部署DHCPv6服务器，可以选择cisco的CNR。

欢迎大家来我的网站来学习和探讨cisco网络技术。

To your success,

Charles Ross, CCNP #CSCO10444244 is the owner of Ittechtips.com; where you’ll find free comprehensive information and videos

about IPv6 technology and how it works with Cisco Systems technology.

Sign-Up for “18 Free Videos” that will teach you IPv6 Address Representation In Under 10 Minutes! at his website.

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翻译者总结：

当前IPv6地址自动配置可以有有状态和无状态之分。

有状态是指在DHCP服务器中保存已分配的IPv6地址信息，无状态是指客户端通过RA通告得到网络前缀和其他信息。

DHCPv6 不支持默认网关的分配。

RA 通告不支持DNS分发(正在实验并讨论中……)

DHCPD最新版4.2.0P2已经支持DHCPv6部分功能。

参考资料第三篇给出了DHCPv6和RA结合使用的案例

参考资料四给出了RA通告情况下DNS服务器的获取情况