Cisco Support Community
Community Member

Dot1Q tunneling and routing

I am in the process of designing a dot1q-tunnel-based service backbone. Basically client switches will uplink with tunnelled ports on the provider backbone.

--------- ------ ----- ------

Cl-SW1 |----|P-SW1|----|P-SW2|-----|Cl-SW2|

--------- ----- ----- ------

Assume that the CL-SW1 is at the headquarters of the client and some traffic from the client should be sent off-premisess (Internet for example) using the same link (Gig Ethernet).

What are my options?

P-SW1 and P-SW2 will not be able to see layer 3 information from the client switches since traffic is layer2-tunnelled. How can I route traffic off the backbone?

I thought about trunking a single port on P-SW1 and connecting it to a router. On the router sub-interfaces will do the job. But the problem is that trunked traffic will reach the router encapsulated with dot1q tunneling? Does a 7600 series router do the job, since it understands tunneling?

Any ideas will be appreciated.


Re: Dot1Q tunneling and routing

It depends upon which switch you are using , If you are using a L3 capable switch , routing can be done on the switch it self , or if its a pure L2 switch you may have to create VLANs and route using sub-interfaces in the routers.Use these links for more details.

Community Member

Re: Dot1Q tunneling and routing

Hi !

Excuse me, perhaps I'm stupid, but I can't understand - how we can route traffic on the same switch even if it is L3 switch as 3550. Because the traffic is tunneled and the switch doesn't know that there are. What customer VLANs with wich IDs are inside and so on... We just have prtovider VLAN's ID for each customer. Do you really offer to create all customer's VLANs on that switch ? Could you explain please ?

Community Member

Re: Dot1Q tunneling and routing

You can route packets that are on the native vlan since they're not tagged. Just configure a Vlan interface for the native vlan and you can then route packets from it. make sure you don't have the 'vlan dot1q tag native' command configured as this will tag frmaes in the native vlan

Community Member

Re: Dot1Q tunneling and routing

Thanks for reply.

But what about such situation: provider has about 10 different customers. He plan to install Metro net based on 3550 switches (ring topolgy 8 nodes), on each node there will be from 3 to 8 customers. Internet access will be from one central node. Following your plan of using native vlans, all customers on each node will share one Internet link -native vlan, isn't it ?

CreatePlease to create content