VLAN is a group of devices/users physically connected to one or more switches, but they are logically separated. All devices in a single VLAN receive broadcast sent by a device in that respective VLAN. By default, all interfaces of switch are in a single VLAN or single broadcast domain.
It’s a very simple job to configure VLANs on few switches; you just have to manually access every switch and configure VLANs. But it will be a very tedious job to configure VLANs manually on each and every switch in the large network.
In scenario 1, there are only four switches and it’s easier to access every switch and configure VLANs. But in scenario 2 there are almost 16 switches and if you want to configure them manually, you can do that but it’ll be time consuming.
Also what if you want to add new VLAN in the network, then again you have to access all switches and configure it. To save time & energy we can use VTP.
You just need to configure VLAN on a single switch, which is acting as a server and that switch will propagate VLAN information to other switches on those trunk links.
As in scenario 1, there are only 4 switches, so we can configure VLANs on these switches by accessing every switch.
In scenario 2, there are almost 16 switches, so we need to configure only trunk links between these switches and all VLAN information will automatically propagates on every switch.