VTP

Unanswered Question
Sep 2nd, 2009

Hi,

1. VTP Summary Advertisements are sent every 5 minutes (300 seconds). Is this timer programmable? If yes, how?

2. I have read in Cisco course material that VTP password is stored in MD5 format and can be 1 to 32 ASCII characters long. It's also mentioned that its 16-byte value. Shouldn't it be 32-byte value?

3. The book mentions three types of advertisements viz. 1. "summary advertisements", 2. "subset advertisements" and 3. "advertisement requests from Clients". Can the advertisement requests be sent by a switch configured as server also (3rd type of adverstisement)?

4. Summary advertisements are sent every 5 min irrespective of whether there is any change in the VLAN configuration or not. I believe, subset advertisements are sent only when there is a change in the VLAN configurations. Is my understanding correct?

I have this problem too.
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Peter Paluch Wed, 09/02/2009 - 23:26

Hello,

1.) As far as I know, the VTP timers are not configurable.

2.) The maximum password length might be up to 32 ASCII characters. However, you must take take into account that the password is combined with the contents of the VTP message and this entire "bulk" of data is then MD5-hashed. The MD5 hash produces a 128-bit (that is, 16 bytes) fingerprint. This is probably the source of that apparent discrepancy.

3.) I suggest reading this document:

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

The types of VTP messages are Summary Advertisement, Subset Advertisement, Advertisement Request and Join messages used for VTP pruning. The Advertisement Request may be sent by both a server and a client - for example, when the VTP domain name is changed.

4.) Yes, that is how I understand it. The summary advertisement serves only a basic/general information function about the state of the VTP domain. However, any particular change willl be transmitted as subset requirements.

Best regards,

Peter

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