ZyXEL Communications VES-1616 manual Vlan Stacking Overview, Company XX branch Company YY branch

ZyXEL VES-1616/24FA-5x Series Support Notes

VLAN Stacking Overview

VLAN stacking allows a carrier to offer multiple virtual LANs over a single circuit. In essence, the carrier creates an Ethernet VPN to tunnel customer VLANs across its WAN. Thus it helps to avoid name conflicts among customers of multiple service providers who connect to the same carrier.

VLAN stacking works by assigning two VLAN IDs to each frame header. One is a "backbone" VLAN ID used by the service provider, the other (up to 4,096 unique 802.1Q VLAN tags) is used by the customers.

The following figure shows a network example.

Company XX branch

Company YY branch

Switch
H	Port 17
VLAN 2		Port		VLAN 30VLAN 2			Port
				Switch		Port	25
		2		B		25
				Port	VLAN 40VLAN 2
				1
	Switch Port 17					2
	A
			VLAN 2

1

							Switch
							E
						Port 17
				Port 25				VLAN 2
					Switch
			VLAN 30VLAN 2				Port
Switch					D
			Port			3 1
C	Port		26
VLAN 40VLAN 2
	27
		Port 25
			Switch G
			Port			Port 17
			1
				VLAN 2			Switch
							F

Company XX HQ Company YY HQ

In this example, company XX and company YY both subscribe to the same ISP for Internet service. Both companies have an internal VLAN group with VID 1. In order to prevent VLAN-tagged packets between these two companies from transmitting to each other’s network, VLAN stacking is implemented in the ISP’s network. The ISP assigns a service provider VID for each company- company XX is assigned an SP VID of 30 and company YY is assigned an SP VID of 40.

The following shows the packet flow between Company XX HQ and its branch

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