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VLAN Questions

VLAN Questions

Hi Everyone,

Why do people tell me not to use VLANs for security purposes?

I have a network, where a have a couple of VLANS. There is a firewall between the 2 VLANs. I am using HP Procurve 1800-24G switches and have made sure that switch-to-switch links accept tagged frames only and that host ports don't accept tagged frames (They are not "VLAN Aware"). I've also made sure that the native VLAN (PVID) of the trunk links are not the same as either of the 2 host VLANs. I've also enabled "Ingress Filtering". Furthermore, I've made sure that host ports are only members of a single VLAN, which is the same as the PVID of the respective port. The only ports which are members of multiple VLANs are the trunk ports.

Can someone please explain to me why the above isn't secure? I believe I've addressed the double tagging issue..

Also, what does "Ingress Filtering" actually do? According to the manual, frames are dropped regardless of whether IF is enabled or disabled, if the port isn't a member of the tagged VLAN..

Pieter 't Hart
Honored Contributor

Re: VLAN Questions

>>> Why do people tell me not to use VLANs for security purposes? <<<

I can agree it should not be the only means used for security.

But if you look at NAC (Network admission control) this technique relies on separating users in vlans based on authentication.
So yes vlan's is an addition to your security.

Shane Mitchell
Occasional Visitor

Re: VLAN Questions

How would I use VLAN's or trunking to restrict traffic from each port (2-7)to port 1 ONLY. I have an Internet connection on Port 1 and the clients on ports 2-7 do not need to talk to each other (and it is preferable not to).
Pieter 't Hart
Honored Contributor

Re: VLAN Questions

Hi Shane,
I think you better have started a new discussion.
if you search this forum you'll find many discussions allready matching your question.

but in short, it would depend on the possibilities of your components (eg the exact model of your switch).
some switches support port-based-acl.
If so you can restrict trafic between ports.
Others models you may treat each port as a subnet/vlan and resttrict access using Racl's.