vtp server

Quick question about default vtp setup.

What is/are the facts that a switch will start to advertise its configuration to other switch?

1. They must have the same vtp domain configured (default one won't work).
2. and? what else?

My point is: because they have vtp server mode configured by default, I don't have to enter the command "vtp server" again to make them starting to exchange configs?

Do you agree? Or am I screwing something?

Thank you.

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Comments

NeonNoodle

I think as long as there is at least one switch which is a vtp server and all the switches are configured to be in the same vtp domain then they will have the same VLAN information. If there is any trouble check the trunking and cabling and check to see if any switches have a vtp transparent configuration.

SanKuKaï

Thanks for your reply NeonNoodle.

I am trying to simulate that with Boson, no cable problems though

Do you think that a show vlan would be enough to see the configuration on the other switches I didn't configure? btw, they have a vtp server default config as well (show vtp status).

NeonNoodle

Yes, I think a show vlan is sufficient to know that vtp is working.

SanKuKaï

Apart from show vlan, what can I try to verify that vtp is working?

Netstudent

make a change on the server, view the revision number. Then go to a client and see if it has the same revision number.

dtlokee

The default VTP domain is "null" meaning there is no domain, if this is the condition of the switch it will not exchange VPT messages with other switches. Now if you have 2 or more switches connected together by trunk ports (remember VTP advertisements are only sent on trunk ports) and you set a domain name on one of them, the others (which are null) will automatically pick up that domain name once the first advertisement is sent.

SanKuKaï

I think I already had those points, but thank you to make them even more clear.

Now I know from where my problem is coming --> BOSON

APA

I was of the understanding that VTP advertisements will not be accepted unless the VTP Clients are set to the same VTP Domain as the VTP Server.

If your server has a VTP password set and the client has the right domain but no password then VTP advertisements will still not be accepted....

VTP Mode changes automatically once VTP advertisements are received though.

If your VTP client has the correct VTP domain and VTP password (if you have one set on your VTP server), but it has a higher revision number than the VTP server then you run the risk of wiping out your whole VTP domain......

Mate.... try show vtp password and see whether there is a password set..... Also run show vtp status to see whether your devices are running the same VTP Mode if you aren't then you will have to manually change the vtp mode through the vlan database with vtp v2-mode command... Although if you have a VTP server this should auto change the clients VTP mode....... But we are talking about buggy boson here......

Hope this helps

SanKuKaï

Yes, that was my thought too...

You must have the same vtp domain name or adverts won't exchange.

APA

glenus,

Proper way to setup VTP Domain is to have one VTP Server and too set all your other switches to VTP Clients with the vtp client command.

This will ensure your revision number always stays the same throughout the domain as you will only be able to make vlan database changes from the VTP Server.

Having all switches as VTP Servers can be risky as what happens if someone accidently makes a change on one of the switches unknowingly and you happen to lose a few vlans or lose your whole vlan database????

Major Trouble!!!

Netstudent

If you have taken all this advice and it still does not work, then do the VTP lab that is pre-built into Boson. If it works, then you know it was a bug in the sim.

This same thing happened to me.

r_durant

dtlokee wrote:

The default VTP domain is "null" meaning there is no domain, if this is the condition of the switch it will not exchange VPT messages with other switches. Now if you have 2 or more switches connected together by trunk ports (remember VTP advertisements are only sent on trunk ports) and you set a domain name on one of them, the others (which are null) will automatically pick up that domain name once the first advertisement is sent.

Sorry to bring back up an old post, but DT (or anyone else)...Out of the box, if I set the domain on one switch and have null on the other, would the null domain switch pick up the domain name and assigned VLANs if there is no IP set on a VLAN interface on both switches, like VLAN 1 for instance?

r_durant

Ok, the reason why I had asked that question, was because I had a two switch setup and and the null switch took really long to get the domain name and the assigned vlans, so I went ahead and assigned an IP to vlan1 interface on both switches, then I saw the update on the previously null switch.

So after I posted the question, I decided to add another switch and just let it wait indefinitely without adding config besides the trunk port config and it did update after a while...

So, my question now is...

How long do these switches take to get the updates when they are newly added as a trunk?

Is this "update" also called convergence (as with STP and routing protocols)? Or, is the vlan database just "updated"?

dtlokee

r_durant wrote:

Ok, the reason why I had asked that question, was because I had a two switch setup and and the null switch took really long to get the domain name and the assigned vlans, so I went ahead and assigned an IP to vlan1 interface on both switches, then I saw the update on the previously null switch.

So after I posted the question, I decided to add another switch and just let it wait indefinitely without adding config besides the trunk port config and it did update after a while...

So, my question now is...

How long do these switches take to get the updates when they are newly added as a trunk?

Is this "update" also called convergence (as with STP and routing protocols)? Or, is the vlan database just "updated"?

VTP updates are sent ever 5 minutes or when there is a change to the database, you may need to wait for 5 minutes. VTP is not dependent on IP to work, it is a layer 2 protocol operating on the default vlan (vlan 1). An update is basically a copy of the vlan.dat file in flash. it sends the whole thing every time, no incremental updates.

r_durant

Ok great, so this brings me to another question...

Maybe I've read about this and forgot, or just didn't read about it at all...but what happens if there's only one server on the switched network and that server goes down, how does the lack of updates affect the clients and the network as a whole? Since the clients do not keep a copy of the database...

dtlokee

r_durant wrote:

Ok great, so this brings me to another question...

Maybe I've read about this and forgot, or just didn't read about it at all...but what happens if there's only one server on the switched network and that server goes down, how does the lack of updates affect the clients and the network as a whole? Since the clients do not keep a copy of the database...

This is one of the shortcommings of VTP, as long as the clients are not rebooted, you are fine. If you reboot the clients or there is a power outage or whatever you may not have a vlan database.

r_durant

dtlokee wrote:

This is one of the shortcommings of VTP, as long as the clients are not rebooted, you are fine. If you reboot the clients or there is a power outage or whatever you may not have a vlan database.

So contrary to what I have read, it "may be" a good idea to have another VTP server (or to have 2) on the network, based on this deficiency...obviously, having both locked down, secret passwords, vtp password for the domain, etc...