Using GS308Ts How to VLAN Cable Modem and LAN?

[HammerG]

I'm trying to get the output from a cable modem to another floor using 2 GS308T smart switches.

Additionally, the LAN will need to be passed to the same location.

I believe I'll need an input port for the cable modem then trunk two VLANs to the far end.

But, I've tried several configuration with no success.

The cable modem never responds when it is connected to the near end switch port.

The far end is a router and it never gets an IP from the modem.

If I run the switches with out VLANs the router pulls an IP without problem.

So, it's my config and I'm looking for suggestions.

[HammerG · Accepted solution]

Well, that might get the cable modem to the far end, but would leave the LAN without connectivity on one side.

So, this is what works.

VLAN 10 -INet

VLAN 20- LAN

change management VLAN to 20

On the modem facing switch:

Ports 1-6 Add VLAN 20 untagged, remove VLAN 1 PVID 20

Port 7 Add VLAN 10 and VLAN 20 tagged, remove VLAN 1

Port 8 Add VLAN 10 untagged PVID 10

On the router facing switch:

Ports 1-6 Add VLAN 20 untagged, remove VLAN 1 PVID 20

Port 7 Add VLAN 10 and VLAN 20 tagged, remove VLAN 1

Port 8 Add VLAN 10 untagged. PVID 10

All works well, router get an IP from the cable modem, LAN is present on both switches.

As a bonus, this is working through a pair of 2.5Gb MoCA devices as there is no way to run cables between each location. At least, not affordably.

[schumaku]

The cable modem is a pure modem (not a router), and the ISP does allow -one- public IP address only (sometimes two). One might guess the public IP addresses are already "used" by the one or two switches.

For extending a WAN part of a cable modem, either use a direct cable, or if required a VLAN configured with a single access port on each side, and avoid the switch management VLAN using DHCP for this simple link.

[HammerG]

There are no switches in the path save the Netgear.
But, I have tested this with a second router that is unable to get a DHCP address from the existing LAN through the VLAN as I set it up.

This did work through a now defunct Microtik pair of switches. Those are way different from the Netgear equipment in configuration.

[schumaku]

So what's' the intention with these two GS308T switches then? If not doing something smart, and have these in the WAN link side of a cable Modem, these will capture two public IP addresses ...

Afraid, I can't understand what for you run a test with yet another NAT router....

[HammerG]

I think your missing the point.
Neither Netgear uses DHCP. Neither get or try to get any address.

If I connect a router in to either and connect the cable modem to that switch as well, the router gets an IP from the router.

What I'm trying to do in essence is to extend the modem's port to a router in a different area via VLAN. Trunking will allow the LAN to be in each Netgear as well

[schumaku]

Create a trunk between the two switches, for example for the VLAN 1234, [T]agged (and nothing else), and two access ports for the VLAN 1234 as [U]ntagged, PVID 1234 (and again nothing else) ... for connecting the modem resp. the other router. 

[HammerG · Accepted solution]

Well, that might get the cable modem to the far end, but would leave the LAN without connectivity on one side.

So, this is what works.

VLAN 10 -INet

VLAN 20- LAN

change management VLAN to 20

On the modem facing switch:

Ports 1-6 Add VLAN 20 untagged, remove VLAN 1 PVID 20

Port 7 Add VLAN 10 and VLAN 20 tagged, remove VLAN 1

Port 8 Add VLAN 10 untagged PVID 10

On the router facing switch:

Ports 1-6 Add VLAN 20 untagged, remove VLAN 1 PVID 20

Port 7 Add VLAN 10 and VLAN 20 tagged, remove VLAN 1

Port 8 Add VLAN 10 untagged. PVID 10

All works well, router get an IP from the cable modem, LAN is present on both switches.

As a bonus, this is working through a pair of 2.5Gb MoCA devices as there is no way to run cables between each location. At least, not affordably.