Using a switch with 2 subnets

MJoshi · 11-07-2009, 04:34 AM

Is it possible to use a switch with 2 subnets?

The application is VoIP and data to run on 2 different subnets which have separate dedicated Broadband lines. The two Broadband routers will be connected to the same switch.

I would like to route the VoIP traffic to the Broadband router and data traffic to the data router using a switch?

The switch I intend to use is the Netgear Smart FS728TP as it has PoE on all 24 ports and VoIP prioritisation.

Thanks.

theevilsharpie · 11-07-2009, 06:41 AM

Yes, it's possible. Since you have a managed switch that supports VLANs, I suggest created a VLAN for VoIP and data, assigning switch ports to the VLAN as needed, and then setting up your QoS settings for each VLAN.

somethingsketchy · 11-07-2009, 11:08 AM

If you have a managed switch, then you are able to create and direct traffic onto two different subnets. Otherwise you would have to use a router to manage the traffic correctly.

imagoon · 11-09-2009, 01:41 PM

A managed switch will allow you to isolate VLANs. However a "layer 3 switch" otherwise known as a router on a switch is required to move data between both subnets. However it appears (from what I can tell) that you are using 2 different web routers with 2 different internet connections. So as long as each router is on a separate vlan that is reachable by each device it should work. Some switches even allow for a certain level of "auto config" to let devices choose which vlan they connect to. IE data > vlan 100 voice > vlan 200.

MJoshi · 11-19-2009, 07:49 AM

I spoke to Netgear tech-support and they have told me that with any Layer 2 switch, it is not possible to support 2 subnets on separate VLANs?

I was told that I would need a Layer 3 switch for this? However, I do not want to route traffic between the 2 subnets.

They said that it is only possible to group ports on a Layer 2 switch. Both VLANs must be on the same subnet?

Am I being given the correct information? I just want to have 2 subnets grouped separately and the Broadband routers will be performing DHCP to assign the IP addresses on each VLAN.

imagoon · 11-19-2009, 11:04 AM

You need a managed layer 2 switch.

Example of a layer 2 switch with vlans (vlans are a layer 2 service)

http://www.cisco.com/en/US/prod/coll...d80322aeb.html

Specifically:

Virtual LANs (VLANs): Up to 32 VLANs (1000 range) and support for 802.1Q trunking using Cisco Smartports

Basically he was wrong. IP is a layer 3 technology. On a layer 2 switch you can create 2 vlans and run 2 IPX networks over them if you wanted.

theevilsharpie · 11-19-2009, 01:46 PM

Quote:

Originally Posted by MJoshi

Am I being given the correct information?

No. Even on an unmanaged layer 2 switch, you can use multiple subnets. A layer 3 switch is only needed if you want the switch to route between subnets.