Creating vlans on cisco switches is one the most common tasks network engineers do. Vlans are so important that we can hardly do without them. This is because vlans help bring about network security and segmentation. Network engineers put in so efforts into learning how to set up vlans but hardly take out time to learn how to delete these vlans. Well, all thanks to deleting the start-up config. The general opinion that erasing the start-up config and then proceeding to reloading the switch would normal make that switch feel brand new is responsible for this. Administrators have found out, howbeit the hard way, that erasing the start-up config does not erase vlans on a Cisco switch. The question then is how?
It is simple but first you need to understand where vlans are stored on a Cisco switch, then you will appreciate the task of deleting it despite the simplicity. Vlans are store in a special file known as vlan.dat. It is also commonly referred to as the vlan database. Information held in this location can not be deleted by erasing the start-up config. To delete the vlan database on a Cisco switch, simply go to the privilege mode and issue the command #delete vlan.dat, reload the switch and all your vlans will be gone.
For a step-by-step approach on how it is done, see video below.
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