the Difference Between Stateful and Stateless DHCP

關鍵字：IPv6 IPv4 IP DHCP DHCPv6 autoconf IPv6地址 自動分配 自動配置 有狀態 無狀態 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).

在介紹有狀態和無狀態IPv6地址自動配置的區別之前，請允許我先介紹一下DHCP。

DHCP是動態主機配置協議的縮寫，這種C/S方式的協議在IPv4網路中已經廣泛部署併為大家所認可。IPV4 DHCP是在RFC2131中定義的，IPv6DHCP是在RFC3315中定義的，簡單地說，DHCP客戶端從DHCP服務端得到IP地址，加入IP網路，而無需手工干預。當發展到IPv6網路時，就有兩種IPv6地址的自動配置的方式：有狀態地址自動配置和無狀態地址自動配置。

有狀態的地址自動配置是指由DHCP伺服器統一管理，客戶端從DHCP伺服器的地址池中拿到IPv6地址和其他資訊（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).

無狀態地址自動配置是指不需要DHCP伺服器進行管理，客戶端根據網路RA（路由通告）並根據自己的MAC地址計算出自己的IPv6地址。他們一般使用DHCP伺服器來獲取DNS伺服器的地址。

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.

一般情況下，Cisco推薦使用無狀態地址自動配置，cisco路由器並沒有設計DHCPv6伺服器。但是如果你需要在網路中部署DHCPv6伺服器，可以選擇cisco的CNR。

歡迎大家來我的網站來學習和探討cisco網路技術。

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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翻譯者總結：
當前IPv6地址自動配置可以有有狀態和無狀態之分。
有狀態是指在DHCP伺服器中儲存已分配的IPv6地址資訊，無狀態是指客戶端通過RA通告得到網路字首和其他資訊。

DHCPv6 不支援預設閘道器的分配。
RA 通告不支援DNS分發（正在實驗並討論中……）

DHCPD最新版4.2.0P2已經支援DHCPv6部分功能。

參考資料第三篇給出了DHCPv6和RA結合使用的案例
參考資料四給出了RA通告情況下DNS伺服器的獲取情況