Does VLANing increase switch CPU usage / Cause bottlenects?

[Alis_Klar]

Hi,

 

Have been considering VLANing for a while but this thread has put me off. They seem to be saying that VLANing is not done anymore?!?

 

https://mangolassi.it/topic/5584/hp-switches-2530-vs-1950-vs-1920/29

[Chris_Cook]

Probably will increase CPU a little bit, but not to a problem level if that's what your asking. Switches specialise in deciding which ports to send packets to, and a vlan is just another number in the packet header to decide on. There's often specific hardware dedicated to this, and the CPU is used more for the management interface. You may need a more powerful core switch / router to route between VLans/subnets.

 

What does cause over-head is management of the vlans - you need to have good planning and network documentation. Also setting them up can be time consuming unless you use a cloud managed solution like Unifi (which makes vlans stupidly easy). You will also need to look at your DHCP and routing setup.

 

The other benefit is reductions in packets that each host/server has to deal with. Especially for broadcast traffic. It can also help isolate network loops to smaller parts of the network.

 

It all depends on the size of your network and the different types of devices you have - once you start doing BYOD for example its great to section that off on its own vlan. Building management and cctv stuff is also great to put on its own vlan, especially if you can add some firewall/routing rules to limit access to the few PCs that need to access it. For a small office, I probably wouldn't bother, but with a school it does have benefits.

[Davit2005]

It depends what switches you go for. Some MikroTik although having 10Gb ports cannot handle L3 tasks and even bridging. If you consider some of the more powerfull enterprise switches, Cisco, Juniper, HP, etc you should not have a problem.

 

There is nothing wrong with vlans, we have over 1000 of them between about 750 switches. We use 4 chassis series switches as cores at the moment running OSPF in a mesh which host most vlans then more secure vlans are routed at the firewall. This system works, is fairly robust and is quite manageable with newer/refurb locations having stacked top of rack switches. May change model in a few years but not to sure what that will end up like.

 

Planning and documentation is key with some management software which makes admin tasks easier when you have to roll out commands to all the switches which we have done a number of times.

 

There are some security and best practice considerations to stop things like vlan hopping etc. Disabling auto mode ports on switches, not using vlan 1, not having client vlans untagged on trunk links, Disabling unused ports, etc. Not to mention physical security of switches in key areas.

Edited September 11, 2020 by Davit2005