Q-in-Q (dot1q Tunnel) basic config

Unanswered Question
Sep 15th, 2008
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Hi all,

I would like to test Q-in-Q and configure it to transport the vtp and stp for the C-Vlan's across the P-Vlan so that both spanning tree and VTP update to get across the Q-in-Q tunnel.

Here is the config I have on the q-in-q switches :

System MTU size is 1504 bytes

vlan dot1q tag native

interface FastEthernet1/0/47

description intf toward customer

switchport access vlan 150

switchport mode dot1q-tunnel

l2protocol-tunnel cdp

l2protocol-tunnel stp

l2protocol-tunnel vtp

interface FastEthernet1/0/48

description intf toward provider

switchport access vlan 150

switchport mode access

the config is similar on the other switch

I have a square with those 2 switches and 2 customer switches

s1 - s2 - s3 - s4 - s1

the link between s3 and s4 is the QinQ link.

If I cut the link between S1 and S2, both Switches become root switches and dont use the Q-in-Q link.

any help greatly appreciated,


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Giuseppe Larosa Mon, 09/15/2008 - 23:39
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Hello Luc,

the normal setup for QinQ deployment is the following:

SWC1 --- SWC2 --trunk /tunnel-- SWP1 --- trunk/trunk -- SWP2 --tunnel/trunk --- SWC3--SWC4.

the tunnel interface is a L2 access interface towards a customer switch device and not a L2 backbone link and so they need to be deployed in pairs.

Hope to help



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