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VTP scenario:1

Unanswered Question
Jan 7th, 2014
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The scenario is to analyse the VTP messages between a VTP server and a client.

Configuration on VTP server: VTP domain: MATRIX, no password is configured, mode : server

Configuration on VTP client: VTP domain: Default (Null), mode: client, no password is configured.


So i thought when i join these two switches with a trunk port, then at first the server will send a default "Summary Advertisement" without any "Followers Field" set (=0) (I mean the server won't indicate the client, that it will recieve "Subset Advertisement" immediatley after this "Summ Adver").

But what happend is server has sent the "Summary Advertisement" with a followers field set to '1',


VTP events on server switch:

--------

VTP-SERVER#

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up


%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up


VTP LOG RUNTIME: switchport trunk mode on Fa0/1 has changed--->>> (And also what does this line mean exactly, because already i configured this port as a turnk port)


VTP LOG RUNTIME: Transmit vtp summary, domain MATRIX, rev 0, followers 1

   MD5 digest calculated = E3 D7 B0 71 25 29 1A BD 87 04 3A 33 E6 83 69 29


VTP LOG RUNTIME: switchport trunk mode on Fa0/1 has changed


VTP LOG RUNTIME: Transmit vtp summary, domain MATRIX, rev 0, followers 0

   MD5 digest calculated = E3 D7 B0 71 25 29 1A BD 87 04 3A 33 E6 83 69 29



VTP LOG RUNTIME: Summary packet received, domain = MATRIX, rev = 0, followers = 0


VTP LOG RUNTIME: Summary packet rev 0 equal to domain MATRIX rev 0


VTP LOG RUNTIME: Transmit vtp summary, domain MATRIX, rev 0, followers 0

   MD5 digest calculated = E3 D7 B0 71 25 29 1A BD 87 04 3A 33 E6 83 69 29


--------


VTP events on client switch:

--------

VTP-CLIENT#

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up


%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up


VTP LOG RUNTIME: switchport trunk mode on Fa0/1 has changed


VTP LOG RUNTIME: Summary packet received in NULL domain state


VTP LOG RUNTIME: Summary packet received, domain = MATRIX, rev = 0, followers = 1


VTP LOG RUNTIME: Transitioning from NULL to MATRIX domain


VTP LOG RUNTIME: Summary packet rev 0 equal to domain MATRIX rev 0


VTP LOG RUNTIME: Subset packet received, domain = MATRIX, rev = 0, seq = 1, length = 139


VTP LOG RUNTIME: switchport trunk mode on Fa0/1 has changed


VTP LOG RUNTIME: Transmit vtp summary, domain MATRIX, rev 0, followers 0

   MD5 digest calculated = E3 D7 B0 71 25 29 1A BD 87 04 3A 33 E6 83 69 29

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Questions:


1. Since the server switch didn't received any "Advertisement Request" from the client, then how can it send a "Summary Advertisement" with a followers field=1 ? On what basis did the VTP server sent the "Subset Advertisements" to the client ? Because the VTP server doesn't know whether the switch just joined is a client/server and whether if it is in it's domain or not ?


2. In the VTP server events i don't see a log indicating that It has transmitted a VTP "Subset Advertisement" whereas in the VTP client events it is showing a log saying that it received a "Subset Advertisement". Bolded text.


Thanks in advance.


Regards,

Chandu

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