VLAN stacking refers to the stack of the 802.1q tags. It allows the device to add two 802.1q VLAN tags to an untagged user packet or change a tagged user packet into a packet with two 802.1q VLAN tags. The packet with two VLAN tags can be transmitted over the backbone network of the service provider. When the packet reaches the BRAS, the BRAS authenticates the packet based on the two VLAN tags, or removes the outer VLAN tag and identifies the user by the inner VLAN tag
Related Information
The VLAN stacking feature allows the MSAN to add an inner 802.1q VLAN tag and an outer 802.1q VLAN tag to an access user packet. The packet with two VLAN tags is transmitted to the layer 2 switching network, and forwarded to the ISP network according to the outer VLAN tag.
Wholesale service: In a layer 2 MAN, there may be multiple Internet service providers (ISPs). The services of these ISPs need to be provisioned to their users quickly. Therefore, the outer VLAN tag is used to identify the ISP and the inner VLAN tag is used to identify the user. In this manner, different user groups with different outer VLAN tags can gain access to the specified ISP networks and obtain the services provided by the ISPs.
The broadband service of users 1 and 2 and the broadband service of users 3 and 4 are provided by different ISPs. The VLAN stacking feature allows the MSAN to add two VLAN tags to a user packet and forward the user packet to the layer 2 network. The outer VLAN tag is used to identify the ISP and the inner VLAN tag is used to identify the user. The layer 2 switch forwards the user packet to the specified ISP BRAS according to the outer VLAN tag. The ISP BRAS removes the outer VLAN tag and identifies the user by the inner VLAN tag. After being authenticated by the ISP BRAS, the user can access the services provided by the ISP.
