Owner manual
+7(495) 797-3311 www.qtech.ru 
Москва, Новозаводская ул., 18, стр. 1 
111 
Dot1q-tunnel based Internetworking mode 
As shown in above, after being enabled on the user port, dot1q-tunnel assigns each user an 
SPVLAN identification (SPVID). Here the identification of user is 3. Same SPVID should be 
assigned for the same network user on different PEs. When packet reaches PE1 from CE1, it 
carries the VLAN tag 200-300 of the user internal network. Since the dot1q-tunnel function is 
enabled, the user port on PE1 will add on the packet another VLAN tag, of which the ID is the 
SPVID assigned to the user. Afterwards, the packet will only be transmitted in VLAN3 when 
traveling in the ISP internet network while carrying two VLAN tags (the inner tag is added when 
entering PE1, and the outer is SPVID), whereas the VLAN information of the user network is 
open to the provider network. When the packet reaches PE2 and before being forwarded to 
CE2 from the client port on PE2, the outer VLAN tag is removed, then the packet CE2 receives 
is absolutely identical to the one sent by CE1. For the user, the role the operator network plays 
between PE1 and PE2, is to provide a reliable layer-2 link. 
The technology of Dot1q-tuunel provides the ISP internet the ability of supporting many client 
VLANs by only one VLAN of theirselves. Both the ISP internet and the clients can configure 
their own VLAN independently. 
It is obvious that, the dot1q-tunnel function has got following characteristics: 
Applicable through simple static configuration, no complex configuration or maintenance to be 
needed. 
Operators will only have to assign one SPVID for each user, which increases the number of 
concurrent supportable users; while the users has got the ultimate freedom in selecting and 
managing the VLAN IDs (select within 1~4094 at users’ will). 
The user network  is considerably independent.  When the ISP  internet  is upgrading their 
network, the user networks do not have to change their original configuration. 
Detailed description on the application and configuration of dot1q-tunnel will be provided in this 
section. 
SP networks 
P 
PE1 
PE2 
CE1 
CE2 
Trunk connection 
Trunk connection 
Unsymmetrical 
connection 
Unsymmetrical 
connection 
Customer 
networks1 
Customer 
networks2 
On the customer port 
Trunk VLAN 200-300 
This  port  on  PE1  is  enabled 
QinQ and belong to VLAN3 
On the customer port 
Trunk VLAN 200-300 
This  port  on  PE1  is  enabled 
QinQ and belong to VLAN3 










