CCNA: VLANs Topic - Only 1 VLAN per interface?

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Hi Ronnie,

In the VLAN video of CCNA, you mention that only 1 VLAN can only be associated with 1 given port / interface, but you can get around that by doing a DATA VLAN and a VOICE VLAN.

Am I missing something here? From past IT experience, and our current configuration at work, we have numerous access port interfaces that share multiple VLANs. To give you an example, we have a Hyper-V environment where we use the default VLAN 1 for our internal network and we have VLAN 50 for our 2nd domain for the Hyper-V hosts.

This way, we have a untagged VLAN 1, and tagged VLAN 50 on a single port. But if I would want to, I could add yet another tagged VLAN # on the same port / interface. Bear in mind we are currently using HPE ProCurve Switches, but this has to be possible on the CISCO side too besides for the trunk ports.

Can you explain this in more detail?

Thanks,
Peter

@Peter-Kapas,

Ok. On a Cisco switch, how many data vlans can a single port be in? for that fact, how many extra voice vlans can a single port be in? Both instances it is only one. So yes, technically you can have more than one vlan but only if they're different types of vlans. You cannot do what you are implying you can do without trunking.

If it can be done on a Cisco switch as you say, I've not encountered in the physical switch without trunking.

Can you show me a cisco config that shows that you can put a port into multiple vlans without a trunk? do the following on your cisco switch

int fa1/1
switchport mode access
switchport access vlan 10
exit
do show vlan brief
[note the vlan ID displayed.  We created a vlan and you see that it's assigned to vlan 10]

int fa1/1
switchport access vlan 20
exit
do show vlan brief
[note vlan ID displayed, did you notice that fa1/1 was not left in vlan 10 and also in vlan 20 but that physical port was now considered only in vlan 20?]

int fa1/1
switchport access vlan 30,40
[what is the output?  % Invalid input detected...]

You mention hyper-v switches. Well virtual switches treat things differently those rules do not apply to a cisco switch.

Now if you know of another way to put a single port on a cisco switch into multiple vlans...I would say that's cool and be confused at the same time.

Hi Ronnie,

Thank you so much for responding. I appreciate it.

It looks like you are correct about your statement. However, is it possible to use "Trunk" ports to connect directly to a physical server / device instead of a network device?

I did a bit of digging about our HPE ProCurve switches and found this:

https://community.hpe.com/t5/Switches-Hubs-and-Modems/Tagged-vs-Untagged/td-p/4004330#.U5fWWyjLP74

"...an untagged port in a VLAN is a physical member of that VLAN, ie. when you plug your host into that port it is physically connected to that VLAN (also known as an "access port" in Cisco terminology).

A tagged port will normally carry traffic for multiple VLANs from the switch to other network devices such as an upstream router or an edge switch (In Cisco terminology this is called "trunking", HP have no specific term for it)."

So in our particular setup at work, we have a Hyper-V host that is has a Virtual Switch configured on the port of the physical switch that is Untagged VLAN 1, and Tagged VLAN 50. VLAN 1 is used 100% of the time, unless you go ahead and manaully punch in the VLAN 50 in the Hyper-V Network Adapter VLAN settings to VLAN 50.

I'm guessing since we are manually setting the VLAN ID on the computer side, it will accept a trunk port instead of an access port? Or both should work on a server, it doesn't have to be an access port?

Thanks,
Peter

@Peter-Kapas,

Generally, since endpoint devices are not VLAN "aware." They don't care what vlan they're in. In a physical environment all of that is handled on the network device (i.e. switch).

By default Hyper-V host's physical adapter will be in VLAN1 by default. It will be in whatever vlan that is configured on the switchport.

• If you want everything on your virtual switch to be allowed on a vlan you can configure that Hyper-V's Virtual Switch network settings.

• If you only want to allow a single VM to access vlan, you can configure the network settings of the VM.

Your description sounds as if it's behaving as an access port all the time. If you don't move it to VLAN 50, it works on VLAN 1. If you move it to VLAN 50, then it doesn't work on VLAN 1. Like my Cisco configuration, the port is in whichever vlan that was last configured. I'm assuming this is the default behavior.

Thanks for the explanation Ronnie. That makes sense.