Q-in-Q Tunneling

Unanswered Question
Oct 8th, 2014
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Hi,

I am having a problem in my Q-in-Q tunnel.
 

I am creating a Q-in-Q tunnel between 2 Routers 2921 and 2911 which are having HWIC-4ESW and IOS 15.3(2)T1 and these routers are connected via ISP network.
I have configured a Q-in-Q tunnel between these router but it not working according to our need I am adding a Metro Tag on 2921 and this Tag will be removed by 2911 router but it is not removing the Tag due to which my traffic is not moving.

This is my configuration on the devices:

2921 

interface GigabitEthernet0/1.70
 encapsulation dot1Q 70
 ip address 1.1.1.1 255.255.255.252
end
 
 
 
l2tp-class class1
 authentication
 hello 40
 password 7 1311021C05090878
 retransmit retries 10
 timeout setup 400
 
vlan 335
 name vlan335
 
pseudowire-class test
 encapsulation l2tpv3
 protocol l2tpv3 class1
 ip local interface GigabitEthernet0/1.70
 
 
interface FastEthernet0/0/0
 description VPLS 10Mbps
 switchport access vlan 335
 switchport mode dot1q-tunnel
 no ip address
 l2protocol-tunnel cdp
 l2protocol-tunnel stp
 l2protocol-tunnel vtp
 no cdp enable
!
 
 
interface Vlan335
 no ip address
 xconnect 1.1.1.2 1 encapsulation l2tpv3 pw-class test
!

 

 And on 2911 side IP is different 

Now the problem is that when 2921 send's a packet with Metro Tag but 2911 is not removing the Tag. As I want to remove Metro Tag on the 2911 or vice-versa.

Thanks & Regards,
Rahul Chhabra

 

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Alex Sanchez Jimenez Thu, 10/09/2014 - 17:13
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  • Cisco Employee,

Hello Rahul,

Can you please provide more details about your topology?

I see you are combining L2TPv3 with QinQ, why is that? Can you please explain how is everything connected?

Regards,

Alex Sanchez

CCIE R&S #37454

Rahul Chhabra Thu, 10/09/2014 - 17:40
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As we want a layer 2 connectivity to connect our 2 different sites over ISP network.

we are having lan network behind our two 2900 series router so, the traffic from any branch is tagged with a Metro tag and transported towards second site via Xconnect and the 2nd end router will remove this Metro Tag and forward our traffic towards Lan.

but in our scenario traffic from any side which is having a Metro tag on it is not removed by second site's 2900 series router.

we are using L2tpv3 dynamic with pseudowire class to connect both the sites with Xconnect.

And on f0/0 we are tagging or untagging our ttraffic with a Metro Tag but this Metro is not removed at other end but it is added while traffic passes from this interface.

Alex Sanchez Jimenez Thu, 10/09/2014 - 18:02
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  • Cisco Employee,

Rahul,

Thanks for your reply.

Do you know if your ISP has adjusted the MTU to carry the additional bytes used by QinQ?

How do you confirm that the packets are arriving to the destination router but the M-Tag is not being stripped off?

Correct me if I'm wrong, but the traffic comes on VLAN335 and then goes to VLAN70 towards your ISP, you are trying to do a QinQ for VLAN335 on interface F0/0/0 so when traffic comes in that interface the QinQ M-Tag is added (70) to get to the remote switch. Correct?

Thanks,

Alex Sanchez

CCIE R&S #37454

Rahul Chhabra Fri, 10/10/2014 - 06:52
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Thanks for replying Alex
 

for your clarification:

interface FastEthernet0/0/0
 description VPLS 10Mbps
 switchport access vlan 335
 switchport mode dot1q-tunnel
 
This is the interface which is adding a 335 number Metro Tag on the traffic coming from our Lan area 
and
This is the sub-interface with encapsulation towards our ISP
 
interface GigabitEthernet0/1.70
 encapsulation dot1Q 70
 ip address 1.1.1.1 255.255.255.252
end

We captured on our 2nd site that our 2900 series router is receiving two tag between than the Upeer Tag is Metro Tag of 335 and inner Tag is from our Lan area.
Now comes the problem this 2900 series router is supposed to remove this Metro Tag and forward tha traffic with the inner Tag for a particular destination but it is not removing this tag as we are seeing this in our Captures.
 

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