Clarification on VTP

Hi, Greetings and a Good day to you. I need a clarification. Say there are 5 Switches on a LAN (With Static VLANs). Let's call them

1)SWT - A 2)SWT - B 3)SWT - C 4)SWT - D 5)SWT - E

Let's say each on these Switches are interconnect to at least Two of the above mentioned switches. Let's Say two of these Switches i.e. SWT

- A and SWT - B are also connected to a Router.

All of these Switches are on a Single VTP Domain. We do not know how many of these switches are Servers but there obviously is one Switch which acts as a VTP Server Switch. Now one has access to Let us say "SWT - C" which is a VTP client Switch. When I say access I imply on the console with a rollover cable.

Clarification One


Now how do we know from the information on "SWT - C" that which Switches are acting as or deployed as a Server of the VTP Domain.

Clarification Two


Suppose One "VTP Server Switch" is disconnected from the domain for 20 minutes and then reconnect again back, in the 20 minute period what happens to the VLANS on the Domain as a whole.

Some links to Authoritative information would also be helpful. Thanks, CraftWorks.

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I don't know of a way to show which switches are servers without physically going to them and doing a show vtp or show config. You can verify how many vlans they know about, and the domain they are in, but doing a show vtp domain or show vtp status depending on IOS or CAT.

As for a disconnection, it all depends on your architecture. Simply taking away a vtp domain inherently should do nothing, but if that switch also has layer 3 in it (via msfc or l3 switch), then you will be down. If all other switches have connections to the layer 3 owner of the vlans, or redundant connections, then switches will continue to work. All VTP does is distribute a list of vlans along with names, configurations, and numbers to other switches to ensure vlans are synched up across layer 2 switches. If the master goes away, the rest continue to know about the vlans, and will continue to forward traffic as necessary. Provided they can still forward frames that will reach the router (gateway), things should be fine. If however the master is also the router or has the only uplink to the router (since most people make the vtp server the 'core' switch or switches which should be closely aligned with the l3 interfaces), then your network will have impact.

Here is Cisco's documentation:

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