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Routing a DSL connection over Cisco Infrastructure

We want to route a DSL connection from one switchport (connected with a DSL Router) of a Cisco Catalyst 3650 in the bureau space to one switchport (connected with a end-device) of a Cisco Nexus environment (5548/2248) in the technical room. The dsl connection should only be available on this two switchports and should not have interaction with the internal network. Our idea was to set up a separate VLAN for the dsl connection. Is this the right way? Is it possible to route the DSL connection over a configured trunk port (Cisco Catalyst) to a configured trunk port (Cisco Nexus) only in this specific VLAN?

Hall of Fame Super Blue

Re: Routing a DSL connection over Cisco Infrastructure


Yes you can have a dedicated vlan for this connection.

You simply create a new vlan and extend it all the way back to the switchport that connects to the end device.

If the end device is only going to be used to connect via the DSL ie. it does not need connectivity to any other devices in any other vlans then there is no need for any SVIs for that vlan. You simply set the default gateway of the end device to be the DSL router.

So the only ports in that vlan are the DSL router and the end device. The trunk links between switches also need to allow this vlan.

With this setup the end device would only be able to communicate with the DSL router and nothing else.


Community Member

Re: Routing a DSL connection over Cisco Infrastructure


Thanks for the answer. Seems that i had the right idea. My concern was that the end devices in the other VLANs get the IP adresses of the DSL Router (with activated DHCP) if i choose the wrong configuration.

One more question:

Do i have to configure both switchports - the one connected to the DSL router and the one connected to the end device - as trunk ports and configure the 'DSL - VLAN' (VLAN 112) as Trunking VLAN?

Like this:

Name: Gi1/0/47

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: down

Administrative Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 200 (client neu)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: 17 (VOIP-OG1)

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk associations: none

Administrative private-vlan trunk mappings: none

Operational private-vlan: none

Trunking VLANs Enabled: 112

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL


Hall of Fame Super Blue

Routing a DSL connection over Cisco Infrastructure


You don't need to configure the switchports connecting to the end device and the DSL router as trunks. You just configure them as access ports in vlan 112.

The switch interconnects are presumably trunks so you need to -

1) make sure vlan 112 is in the vlan database on both switches


2) allow vlan 112 on the trunk links

and there should be no SVIs  for vlan 112 on either switch as they are not needed.

This would mean only the end device and the DSL router are in vlan 112 and no other device could get a DHCP address from the DSL router.


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