Relating VTP roles & Messages

[chandra_rc16]

1. So any switch it may be a VTP Server/Client it can send the "Summary Advertisements" for every 5mins ?

2. If the topology is like this: SERVER----CLIENT1----CLIENT2 (Client2 Joined just now), then proabably Client2 wil generate an "Advertisement Request" as soon as it joins the domain. So Client1 can send the "Summary Advertisement" first and then "Subset Advertisement" to Client2.

There is no exemption that each and every switch that joins the domain must receive the "Summary/Subset Advertisements" from only Server switch? Correct me if i'm wrong.

So the roles: Server, Client, Transparent are only required to tell their VLAN configuration capabilities. I mean the Roles are only used to identify whether it can add/remove VLANs for itself or for the enitre domain or not at all.

Thanks in advance

Regards,

Chandu

[chandra_rc16]

And even i just did a PT lab with a client & a server switch.

The client has 9 VLANs inlcuding he default 5. Whereas the server only has default5 vlans. The server acquired all the VLANs from client.

So can someone please clear  my above doubt and this one ...

Regards,

Chandu

[chandra_rc16]

I know only this place to ask this question.

Can someone clarify this ?

Regards,

Chandu

[Rolf Fischer · Accepted solution]

Hi Chandu,

1) Correct: VTP servers and clients send Summary Advertisements every 5 minutes.

[EDIT]: Provided that the Configuration Revision is greater than zero, otherwise there is nothing to advertise.

2) When a new switch joins the domain, there are some variants.

If a trunk becomes operational, the new switch will send Advertisement Requests to learn the domain's vlan information as soon as possible. When the domain name and (optional) passwords match, a neighbor switch will immediately reply with Summary and Subset.

If not, the new switch will have to wait until another switch sends a regular periodic Summary Advertisement (5 min interval; "last resort").

When the new switch's domain name is still Null, it will set its domain to the domain learned from the received VTP message. It then will send an Advertisement Request which will be replied by Summary and Subset.

A reset (changing domain name) also triggers a switch to send a Summary Advertisement at once.

When the domain name and (optional) passwords match and  the receiving switch has a configuration revision > 0, it will reply with its own Summary Advertisement.

It is a common misunderstanding that only VTP servers can update other switches VLAN database. A Summary Advertisement sent by a VTP client with a higher configuration revision will be accepted by a receiving VTP client/server. However, an update event will normally be triggerd by a VTP server within the domain, as only the server mode allowes the actions that increment the Configuration Revision (add/rename/delete/suspend VLANs), but the information will be relayed by switches in client- and transparent mode as well.

Note that VTP is a proprietary protocol and Cisco doesn't publish all the details of protocol operation.

So some of the mentioned behavior is just based on observations and may vary depending on platform/IOS.

HTH

Rolf

[chandra_rc16]

Yes you are right..... even i observed that depending upon the scenario the switches are generating Advertisement Request and some time first summary advertisements....they're varying themselves as per the situation.... if a trunk is coming they are using some type of method to populate vlans and if a new client is joining it's using some other method sometimes.....

So, i think we just need to understand the use of the messages, and know a bit not deep about the various situations and the vtp messages? right ?

And really a lot of thanks for you... because i was getting deep into the VTP messages.. and as much as i anlayse them.. they're confusing me.....:)

Regards,

Chandu