Need help with a vlan issue

linux11mad · ‎08-23-2010

Hi everyone,

I bought SLM224G switch a little while ago now and its great but i am having a issue with routing internet though to different vlans that i have created. I have 2 vlans at the moment and they are working great but i have plugged 2 ethernet cables from the router to either vlan so that each vlan can get the internet but my issue is that if 1 cable is plugged in one vlan the internet works fine but when plugging in the other cable into the other vlan the internet cuts off of the vlan that was working and the one i plugged in after gets the internet fine.

Sorry if this is a stupid question but am i doing something wrong or am i thinking wrong on how this the idea is put together.

Any help will be great.

Many thanks

kyukim · ‎08-23-2010

Hi,

Have you assigned different ip address for each router port that connected to SLM224G switch?

If you have a l2 switch with 2 vlan and you connet a router to two different vlan ports on L2 sw, then you need to make sure router port's has different IP address for each vlan and SW should put ports connected to router into correct vlan.

KK.

Peter Paluch · ‎08-23-2010

Hello Paul,

You have not indicated any technical data so I just have to guess what can be your problem, so treat this as a couple of suggestions.

First, you have to take care that each VLAN is a separate IP subnet. Do not use the same IP network in both VLANs.

Also, you have indicated that you have selected one port in each VLAN to be connected to a router that provides an access to the internet. What is the type of that router? Does it have two separate interfaces itself, or just a built-in switch? Note that plugging ports in two VLANs to two port in a built-in switch of a router makes these two VLANs to leak one into another.

Ideally, if your router supports 802.1Q frame tagging and creation of subinterfaces, you could use a single port on your switch for an arbitrary number of VLANs (a so-called trunk port) and for each VLAN, create a logical subinterface on your router. This way you would save ports because a single port would be enough for this inter-VLAN routing to work.

If you need more information please don't hesitate to ask, however, please attach a diagram of your network along with the addressing information.

Best regards,

Peter

linux11mad · ‎08-23-2010

Hi,

Thanks for the quick reply.

I am not a professional and i am just learning at the moment so bear with me. I think i have realized what the issue is from what you both have said, the routers i have and tried with both same effect are standard routers Linksys BEFSR41 and a Netgear prosafe VPN Firewall FVS318. Which i am guessing thats why its not working, plus there on the same subnet (192.168.1.x as the routers can not seperate into 2 or more subnets. I guess its possible though to plug all the vlans into different interfaces cards on a machine then that machine will be able to route the traffic etc and plugging the router into another interface card so it looks like :

modem ------- router-----------machine -------------------------------------------vlan 2

-------------------------------------------vlan 3

-------------------------------------------vlan 4

and so on , is this possible ? if not what router models support seperating for ports to subnets etc

Thanks again for your help!

kyukim · ‎08-23-2010

Hi, Paul.

Yes, you can do it if your machine has several network cards.

Modem-----Router(NAT device)---different vlan and different IP subnet ----PC or Server (default gw for each vlans and routing enabled)====different vlans.

If your PC or server can support routing, then create default static route pointing to Roiuter's internal ip address.

Also, you need vlan 5 between PC and rouiter.

KK.