报文的目的地址中自动获取隧道终点的 IPv4 地址，这样的隧道称为“自动隧道”。 如 表 1-1 所示，根据对IPv6 报文的封装方式的不同，IPv6 over IPv4 隧道分为以下几种模式。表 1-1 中还列举了各隧道模式的关键配置参数。
IPv6 over IPv4 隧道两端的设备必须支持 IPv4/IPv6 双协议栈。
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图1-1 IPv6 over IPv4 隧道原理图
IPv6 over IPv4 隧道对报文的处理过程如下： • IPv6 网络中的设备发送 IPv6 报文，该报文到达隧道的源端设备 Device A。 • Device A 根据路由表判定该报文要通过隧道进行转发后，在 IPv6 报文前封装上 IPv4 的报文
• 本文只介绍实现 IPv4/IPv6 过渡的隧道。 • GRE、MPLS TE 的相关介绍和配置请分别参见“三层技术-IP 业务配置指导”中的“GRE”、
MPLS 配置指导中的“MPLS TE”。
1.1.1 IPv6 over IPv4 隧道
1. IPv6 over IPv4 隧道原理 IPv6 over IPv4 隧道是在IPv6 数据报文前封装上IPv4 的报文头，通过隧道使IPv6 报文穿越IPv4 网 络，实现隔离的IPv6 网络的互通，如 图 1-1 所示。IPv6 over IPv4 隧道可以建立在主机—主机、主 机—设备或设备—设备之间。隧道的终点可能是IPv6 报文的最终目的地，也可能需要进一步转发。
头，通过隧道的实际物理接口将报文转发出去。 • 封装报文通过隧道到达隧道目的端设备 Device B，Device B 判断该封装报文的目的地是本设
备后，将对报文进行解封装。 • De文。如果目的地就是本设备，
则将 IPv6 报文转给上层协议处理。
2. IPv6 over IPv4 隧道模式
根据隧道终点的 IPv4 地址的获取方式不同，隧道分为“配置隧道”和“自动隧道”。 • 如果 IPv6 over IPv4 隧道的终点地址不能从 IPv6 报文的目的地址中自动获取，需要进行手工
配置，这样的隧道称为“配置隧道”。 • 如果 IPv6 over IPv4 隧道的终点地址采用内嵌 IPv4 地址的特殊 IPv6 地址形式，则可以从 IPv6
目录
1 隧道配置 ············································································································································ 1-1 1.1 隧道概述············································································································································1-1 1.1.1 IPv6 over IPv4 隧道 ················································································································1-1 1.1.2 协议规范 ·································································································································1-4 1.2 隧道配置任务简介 ·····························································································································1-4 1.3 配置Tunnel接口·································································································································1-4 1.4 配置IPv6 手动隧道·····························································································································1-5 1.4.1 配置准备 ·································································································································1-5 1.4.2 配置IPv6 手动隧道 ··················································································································1-5 1.4.3 配置举例 ·································································································································1-6 1.5 配置IPv4 兼容IPv6 自动隧道 ·············································································································1-9 1.5.1 配置准备 ·································································································································1-9 1.5.2 配置IPv4 兼容IPv6 自动隧道···································································································1-9 1.5.3 配置举例 ·······························································································································1-10 1.6 配置 6to4 隧道 ·································································································································1-13 1.6.1 配置准备 ·······························································································································1-13 1.6.2 配置 6to4 隧道 ······················································································································1-13 1.6.3 配置 6to4 隧道举例 ···············································································································1-14 1.6.4 配置 6to4 中继举例 ···············································································································1-16 1.7 配置ISATAP隧道 ·····························································································································1-18 1.7.1 配置准备 ·······························································································································1-18 1.7.2 配置ISATAP隧道 ··················································································································1-18 1.7.3 配置举例 ·······························································································································1-19 1.8 隧道显示和维护 ·······························································································································1-22 1.9 常见错误配置举例 ···························································································································1-22