what do you guys use VLANs or VRF

[nathanmonteyne0]

Hi Guys,

So with my CCNA you ofcourse learn a lot about VLANs trunking etc.
but while studying for CCNP I was wondering something why would you use VLANs instead of VRF?

I know the differences but I would assume the most uses are with VRF.
As it is Layer 3, you can split the network etc.

Why would someone choose VLANs instead of VRF?

Or when do you use what because for me it would always be VRF.

Kind regards.

[Kasun Bandara]

@nathanmonteyne0 hi, use VLAN to sperate L2 networks and make routable between L2 using SVIs. so you do inter vlan routing easily in VLAN. but you cannot have 2 VLANs with same ip range and make them communicate each other. this is like 2 virtual switches.

if you dont need any inter network routing and only need different L3 segments, go to VRF. in side VRF you can have VLANs. VRF can have sperate routing instances which can have same network ranges independently. this is like 2 virtual routers.

[nathanmonteyne0]

Would it also be possible to use VRF to have redundancy. Like this would only be on port level and not hardware level as you would still have 1 router but I can see this as a cheaper option for redundancy with an uplink if a port is broken or cable is broken

[Kasun Bandara]

@nathanmonteyne0 its depends on the requirement. normally we talk redundancy on HW and SW both. if one of those component is missing, its not redundancy. in VRF, you may utilizing only 1 HW. in case of HW failure its gone. also even VRF have separate routing instances, kernal level is same. so i dont think VRF with 1 hardware is not redundancy. 

[Joseph W. Doherty]

NB: I'm responding from my phone and don't know how to emphasize text, so I capitalized a key attribute; I'm not shouting. ; )

In "real networks", actual common usage is the opposite, i.e. VLANs are common, VRFs are not.

The reason for this is virtualize what was commonly done before VLANs, i.e. having L2 segments interconnected by L3.  VLANs allow L2 segments to be ON THE SAME NETWORK DEVICES.

VRFs, allow for virtual L3 domains, which most don't have a need for ON THE SAME NETWORK DEVICES.

A possible example of VRFs being useful might be a hosting company which provides different client businesses to use the same private IPs, each in its own VRF, but physically ON THE SAME NETWORK DEVICES.