Configuration revision number and VTP server mode

[zillah2004]

What I read are these:

[quote]

Adding a switch configured in VTP server mode and with a revision number higher than the current number in the network could cause the communication problem in the scenario. If the new switch was configured in server mode and the revision number was higher than the current revision number on existing switches, it could cause the rest of the switches to update with the information contained in that new advertisement.

[/quote]

[quote]

The configuration revision of the switch you inserted was higher than the configuration

revision of the VTP domain. --------The overwritten happens whether the switch is a VTP client or a VTP server.

[/quote]

Now for overwritten to occur is it necessary for a switch to be in server mode and higher configuration revision number (two condition) ?

[sachinraja]

Hello zillah...

Yes.. as given higher, the configuration revision number is the one, which shows the newness of any VLAN database.. so, if the config rev is high, it means that the database is new, and it wil overwrite the old database.. the switch should also be in server mode to do so, because only the server mode switches are eligible to propogate VLAN information. all the clients ONLY listen to these messages and update the VLAN database.. So, if the switch is a server and also has a higher config register no, then your network is in real BIG DANGER !!!! Again to emphasis, the conditions are in AND mode, and not in OR mode...

Hope this helps.. all the best. rate replies if found useful..

Raj

[royalblues]

I would not totally agree with sachin on the above point.

Its true that if the switch has a higher revision number then it will overwrite the existing VLAN database.

But it is not necessary that the switch to be in server mode. A switch in client mode with a higher revision would overwrite the VLAN database

Have a look at this flash object which will give you a good understanding of VTP and the common problems associated with it.

http://www.cisco.com/warp/public/473/vtp_flash

HTH, rate if it does

Narayan

[Amit Singh]

Raj,

I slightly disagree with you on this.If the switch is in VTP client state and it has a higher revision number, it can also bring the Vlan database problem in the network.It is not necessary that switch should be in a Server mode with higher revision number to change the vlan database on the other switches.

So that statement goes like this" If the new switch that you are about to introduce in the network is either in VTP server mode or VTP client mode and has a Higher revision number, it can cause the VLAN database overwrite problem on the network"

HTH,Please rate if it does.

-amit singh

[sachinraja]

Amit,

You are right... got a lil confused :)

Raj

[hardiklodhia]

hi,

In addition to what sachin has explained,see this for further understanding..

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml

rgrds,

[sourabhagarwal]

in addition to that, if we are adding a switch which is configured in either server or client mode and having a higher configuration revision number, it will cause problem of overwriting existing VLAN database only if VTP domain of this switch is matching with the VTP domain in which it is going to be added. if VTP domains are not matching then I believe there should not be any problem.

[zillah2004]

Here is the proof to what I had read from the cisco site (in my early thread), I just found it (before i was not able to locate this URL) :

http://www.cisco.com/warp/customer/473/21.html#vtp_ts_cav

The configuration revision number of the switch that you inserted was higher than the configuration revision number of the VTP domain. Therefore, your recently introduced switch, with almost no configured VLANs, erased all VLANs through the VTP domain.

This happens whether the switch is a VTP client or a VTP server. A VTP client can erase VLAN information on a VTP server. You can tell that this has happened when many of the ports in your network go into inactive state but continue to be assigned to a nonexistent VLAN.

[zillah2004]

Now on more question, if we have got more than one switches one VTP version 1, and other VTP version 2, and other Version 3,,,,,all of them have got same configuration revision (not version) numbers,,,,does VTP version affect overwritten ?

[Amit Singh · Accepted solution]

VTPv1 is not compatible with V2. While V3 and V2 are compatible. So might get into some issues as you cannot have all the 3 versions work simultaneously.

HTH,

-amit singh

[sourabhagarwal · Accepted solution]

I feel VTP version won't change at all.

As per VTP configuration guideline, All switches in a VTP domain must run the same VTP version.

check this URL to get more information.

http://www.cisco.com/warp/public/473/21.html#vtp_guidelines

HTH, rate if it does ...

[zillah2004]

Thanks for that