2.2 VLANs and Trunking

What is a Local Area Network (LAN)?

A group of devices in the same broadcast domain.

What is a Virtual LANs (VLANs)?

A group of device in the same broadcast domain separated logically instead of physically.

How are VLAN numbers and names made?

They are configured.

What is a VLAN trunk also known as as?

802.1Q Trunk.

What is a VLAN trunk (802.1Q Trunk)?

Single ethernet connection between two switches.

What does a trunk add to a normal ethernet frame?

VLAN header stating which VLAN it’s going to in the frame.

What does a VLAN frame look like?

Preamble, SFD, Destination MAC, Source MAC, VLAN, Type, Payload, FCS.

How long are VLAN IDs?

12 bits long.

What are normal ranges for VLAN headers?

1 through 1005.

What is the extended range of VLAN IDs?

1006 through 4094.

What are the reserved VLAN numbers?

0 and 4905.

What did we have before 802.1Q?

Inter-Switch Link (ISL).

What is the default VLAN?

VLAN assigned to an interface by default.

What is the native VLAN?

VLAN that doesn’t add an 802.1Q Header, connecting switches without a tag.

What is a layer 3 switch?

Switch (layer 2) and router (layer 3) in the same physical device.

What does the internal router on a layer 3 switch do?

Connects to the VLANs over VLAN interfaces.

Why might a layer 3 switch need to be restarted?

You may need to enable routing on it.

Does a layer 3 switch replace a standalone router?

No, a layer 3 switch does not replace a standalone router.

What were cables like in the old school?

Connect computer to switch, connect the phone to Private Branch Exchange (PBX).

What was the cabling like back in the old school?

Two physical cables with two different technologies.

What do we do for VoIP devices now?

Use Voice over IP and connect all device to the Ethernet switch.

What does the cabling now look like?

One network cable for both.

Why don’t voice and data like each other?

Voice is very sensitive to congestion, with data loving to congest the network.

What is solution to voice and data not liking each other?

Put the computer on one VLAN and the phone on another.