06-IP转发基础配置
本章节下载: 06-IP转发基础配置 (111.07 KB)
目 录
1 IP转发基础····································································································································· 1-1
1.1 IP转发概述····························································································································· 1-1
1.1.1 IP转发简介···················································································································· 1-1
1.1.2 IP转发表······················································································································· 1-1
1.2 IP转发表显示和维护················································································································ 1-2
在以下的介绍中所指的路由器,代表了一般意义下的路由器以及运行了路由协议的以太网交换机。为提高可读性,在手册的描述中将不另行说明。
对于不同网络之间的互连通信,可能会使用不同的传输介质和不同的链路层协议,为了提供更大的灵活性,我们通常使用网络层地址即IP地址来进行通信。
路由器收到一个IP报文后,根据报文的目的地址查找转发表,指导IP报文进行转发。
转发表,即FIB(Forwarding Information Base,转发信息库)表。
路由器通过路由表选择路由,把优选路由下发到FIB表中,通过FIB表指导IP报文转发。FIB表中每条转发表项都指明了要到达某子网或某主机的报文的下一跳IP地址以及出接口。
路由表的具体内容,请参见“三层技术-IP路由配置指导”中的“IP路由基础”。
通过命令display fib可以查看FIB表的信息,例如:
<Sysname> display fib
Destination count: 6 FIB entry count: 6
Flag:
U:Useable G:Gateway H:Host B:Blackhole D:Dynamic S:Static
R:Relay
Destination/Mask Nexthop Flag OutInterface InnerLabel Token
192.168.1.0/24 0.0.0.0 U Vlan999 Null Invalid
192.168.1.40/32 127.0.0.1 UH InLoop0 Null Invalid
......(省略部分显示信息)
FIB表中包含了下列关键项:
· Destination:目的地址。用来标识IP报文的目的地址或目的网络。
· Mask:网络掩码。与目的地址一起来标识目的主机或路由器所在的网段的地址。将目的地址和网络掩码“逻辑与”后可得到目的主机或路由器所在网段的地址。例如:目的地址为192.168.1.40、掩码为255.255.255.0的主机或路由器所在网段的地址为192.168.1.0。掩码由若干个连续“1”构成,既可以用点分十进制法表示,也可以用掩码中连续“1”的个数来表示。
· NextHop:转发的下一跳地址。
· Flag:路由的标志。
· OutInterface:转发接口。指明IP报文将从哪个接口转发。
· InnerLabel:内层标签值。
· Token:LSP索引号。
查看转发表的信息是定位转发问题的基本方法。在任意视图下执行display命令可以显示转发表信息。
表1-1 IP转发表显示和维护
操作 |
命令 |
显示FIB信息 |
display fib [ multiple-topology topology-name | vpn-instance vpn-instance-name ] [ acl acl-number | ip-prefix ip-prefix-name ] [ | { begin | exclude | include } regular-expression ] |
显示与指定目的IP地址匹配的FIB信息 |
display fib [ multiple-topology topology-name | vpn-instance vpn-instance-name ] ip-address [ mask | mask-length ] [ | { begin | exclude | include } regular-expression ] |
不同款型规格的资料略有差异, 详细信息请向具体销售和400咨询。H3C保留在没有任何通知或提示的情况下对资料内容进行修改的权利!