VTP domain is automatically configured

I have three switches: SW1, SW2, SW3

I set domain on SW2 and activate its trunking interfaces.

Now SW1 and SW3 autoconfigure themselves with domain name of SW2.

Why?

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Chitownjedi

I am studying for my ICND2 and I am literally reading this section right now.. is it because they are set to dynamic auto and whatever Switch has trunking configurations will cause those set to auto negotiate to configure themselves for communication? And is the original switch2 set up as a vtp server?

lordy

When the VTP domain name is empty, it will join the first VTP domain it learns about. This is expected behavior.

If you want to avoid this you can set the VTP mode to transparent.

Chitownjedi

mguy wrote: »

I have three switches: SW1, SW2, SW3

I set domain on SW2 and activate its trunking interfaces.

Now SW1 and SW3 autoconfigure themselves with domain name of SW2.

Why?

Indeed the next page just listed that if a domain name is set, then that switch will start sending vtp updates immediately, and any switch connected with a null domain name, will begin using that domain name (with no password configured).. so that is default behavior

MickQ

Be careful about two things in particular.
1. a switch with no VTP config on it (just fresh out of the box/deleted vlan.dat) will assume the domain name and details of the first VTP domain it encounters (via trunked links, naturally).
2. a switch with a higher config revision number will spread its vlan database to other switches in its domain, when it's booted/reloaded. This INCLUDES switches in client mode. Test it in your own lab

NetworkVeteran

mguy wrote: »

Now SW1 and SW3 autoconfigure themselves with domain name of SW2.

Why?

To make basic network administration easier! They expect most admins aren't CCIEs.