随着以太网技术在网络中的大量部署,利用VLAN对用户进行隔离和标识受到很大限制。因为IEEE802.1Q中定义的VLAN Tag域只有12个比特,仅能表示4096个VLAN,无法满足城域以太网中标识大量用户的需求,于是QinQ技术应运而生。QinQ(802.1Q in 802.1Q)技术是一项扩展VLAN空间的技术,通过在802.1Q标签报文的基础上再增加一层802.1Q的Tag来达到扩展VLAN空间的功能。如下图所示用户报文在公网上传递时携带了两层Tag,内层是私网Tag,外层是公网Tag。
单个终端用户可溯源。每个终端一个独立的二层广播域,最大限度地限制BUM流量对网络造成的影响。终端用户到BRAS设备之间二层互通,匹配PPPoE等认证需求。
[SW1] vlan batch 100 200
[SW1] interface GigabitEthernet 0/0/1
#配置GE0/0/1外层TAG为100
[SW1-GigabitEthernet0/0/1] port link-type dot1q-tunnel
[SW1 -GigabitEthernet0/0/1] port default vlan 100
[SW1] interface GigabitEthernet 0/0/2
#配置GE0/0/2外层TAG为200
[SW1-GigabitEthernet0/0/2] port link-type dot1q-tunnel
[SW1-GigabitEthernet0/0/2] port default vlan 200
[SW1] interface GigabitEthernet 0/0/3
[SW1-GigabitEthernet0/0/3] port link-type trunk
[SW1-GigabitEthernet0/0/3] port trunk allow-pass vlan 100 200
#配置外层VLAN tag的TPID值
[SW1-GigabitEthernet0/0/3] qinq protocol 9100
[SW1] vlan batch 2 3
[SW1] interface GigabitEthernet 0/0/1
[SW1-GigabitEthernet0/0/1] port link-type hybrid
[SW1-GigabitEthernet0/0/1] port hybrid untagged vlan 2 3
[SW1-GigabitEthernet0/0/1] qinq vlan-translation enable
[SW1-GigabitEthernet0/0/1] port vlan-stacking vlan 100 stack-vlan 2
[SW1-GigabitEthernet0/0/1] port vlan-stacking vlan 300 stack-vlan 3
[SW1-GigabitEthernet0/0/1] quit
[SW1] interface GigabitEthernet 0/0/2
[SW1-GigabitEthernet0/0/2] port link-type trunk
[SW1-GigabitEthernet0/0/2] port trunk allow-pass vlan 2 3
[SW1-GigabitEthernet0/0/2] quit