vtp version 2 and vtp domain

Answered Question

switchA ---- B ---- C

3 switches connected one-by-one

A version2 server domain:cisco

B version2 transparent domain:test

C version2 client domain:cisco

according to the documentation,we can conclude that C will learn vlan information from A. but the test is fail.

why ?

"Version-Dependent Transparent Mode-In VTP version 1, a VTP transparent switch inspects VTP

messages for the domain name and version and forwards a message only if the version and domain

name match. Because VTP version 2 supports only one domain, it forwards VTP messages in

transparent mode without inspecting the version and domain name."

I have this problem too.
0 votes
Correct Answer by royalblues about 9 years 1 month ago

I just tested it out in my lab and it works fine.

So as Kevin said before you might not have enabled V2 mode on the transparent switch

Your vtp status output on the transparent should show something like this

VTP Version : 2

Configuration Revision : 0

Maximum VLANs supported locally : 256

Number of existing VLANs : 5

VTP Operating Mode : Transparent

VTP Domain Name : test

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled ---- this shud be seen as enabled

VTP Traps Generation : Disabled

MD5 digest : 0x83 0x05 0x5F 0x4F 0x2E 0xC0 0xF9 0xC6

Configuration last modified by 0.0.0.0 at 3-1-93 00:11:52

HTH

Narayan

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Overall Rating: 3.8 (6 ratings)
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Edison Ortiz Fri, 11/09/2007 - 07:38

I don't have the equipment to test right now, but I believe VTP transparent will forward the information as long as the Vlans are created on its database.

Kevin Dorrell Fri, 11/09/2007 - 07:55

This is an interesting problem. The documentation does seem to imply that the domain name of the transparent box does not affect the passing of the VTP messages.

Are you sure there are proper trunks A-B and B-C, and that A and C are properly on the same domain? If you reconfigure B as a client in domain cisco, does C get its updates properly from A?

Secondly, are you sure you are running version 2? The output of show vtp status can be misleading. Could you post show vtp status for each switch?

Kevin Dorrell

Luxembourg

bvsnarayana03 Fri, 11/09/2007 - 08:13

The enhancements in VTP Version 2 are:

Password

Pruning

& support for token rings.

Config revision is same for v1, v2 & v3. though in version 3 its called database revision number.

If devices on same domain share vtp messages, how is it decided which message is the more recent & whether to update the database or not. So config revision plays a major role in synchronisation of database.

In your case, transparent switch is in a separate domain. So if it receives a message with different domain name in its header, switch B should reject because domain names doesnt match.

As far as config revision, here is how it works:

Each VTP instance is associated with a database revision number. The database revision number is incremented when the value of the database that is covered by the advertised checksum is modified.

When a device receives a VTP advertisement from the same primary server for an instance in the same domain, the following occurs:

•If the database revision number in the advertisement is less than that of the receiving device, the advertisement is ignored and a summary advertisement with the current revision number is transmitted on the trunk on which the original advertisement was received.

•If the database revision number in the advertisement is the same as that of the receiving device, the following occurs:

-If the checksum of the advertisement is exactly the same as the checksum of the current configuration known to the device, then no action is taken.

-If the checksum of the advertisement is not exactly the same as the checksum of the current configuration known to the device, the device's configuration is unaffected, but the device indicates to the database manager that a configuration error condition has occurred.

•If the database revision number in the advertisement is greater than that of the receiving device, and the advertisement's checksum and configuration information match, the receiving switch requests the exact subset of databases for which it is not up to date.

Happy Diwali.

rajatsetia Fri, 11/09/2007 - 09:46

Hi,

i am in bit of hurry, so if i mispelled something, kindly bear with me.

VTP V2 , transparent mode switch is capable of propagating the VTP messages from differnt VTP doamin.

at present i have not tested but i think i can rely on justin menga who has clearly explained this in his book of ccnp practical studies : switching

refer to appendix A, self study lap part 1, page 850.

if you dont have the book , u can have preview of this chapter in books.google.com

cheers

btw congrats narayana for ur netpro badge :)

Correct Answer
royalblues Fri, 11/09/2007 - 12:46

I just tested it out in my lab and it works fine.

So as Kevin said before you might not have enabled V2 mode on the transparent switch

Your vtp status output on the transparent should show something like this

VTP Version : 2

Configuration Revision : 0

Maximum VLANs supported locally : 256

Number of existing VLANs : 5

VTP Operating Mode : Transparent

VTP Domain Name : test

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled ---- this shud be seen as enabled

VTP Traps Generation : Disabled

MD5 digest : 0x83 0x05 0x5F 0x4F 0x2E 0xC0 0xF9 0xC6

Configuration last modified by 0.0.0.0 at 3-1-93 00:11:52

HTH

Narayan

rajatsetia Fri, 11/09/2007 - 16:03

this forum is amazing, i have not seen anywhere else, wheer you get reply in such a short time and with actually people testing it in their lab setup

thanks to all the netpros who keep the momentum going and i have learnt a lot from you guys..

rgds

yassine-m Mon, 11/26/2007 - 03:00

I just tested and I confirm VTP V2 transparent mode switch is capable of propagating the VTP messages from differnt VTP domain.

br

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