Clarification on VTP

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Hi,
Greetings and a Good day to you. I need a clarification.
Say there are 5 Switches on a LAN
Let's call them
1)SWT - A
2)SWT - B
3)SWT - C
4)SWT - D
5)SWT - E

Let's say each on these Switches are interconnect to at least Two of
the above mentioned switches. Let's Say two of these Switches i.e. SWT
- A and SWT - B are also connected to a Router.

All of these Switches are on a Single VTP Domain. We do not know how
many of these switches are Servers but there obviously is one Switch
which acts as a VTP Server Switch. Now one has access to Let us say
"SWT - C" which is a VTP client Switch. When I say access I imply on
the console with a rollover cable.

Clarification One
-----------------

Now how do we know from the information on "SWT - C" that which
Switches are acting as or deployed as a Server of the VTP Domain.

Clarification Two
-----------------

Suppose One "VTP Server Switch" is disconnected from the domain for 20
minutes and then reconnect again back, in the 20 minute period what
happens to the VLANS on the Domain as a whole.

Some links to Authoritative information would also be helpful.
Thanks,
CraftWorks.


Re: Clarification on VTP
On 10/28/2007 5:02:41 AM, CraftWorks wrote:

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Issuing the 'show vtp status' command on 'SWT - C' will return information
about VTP from that switch's perspective. Included with that information is a
little bit at the end that says 'Configuration last modified by: <IP> at
<date> <time>'

Whatever IP is listed there is a switch configured as a VTP server.

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It depends. If the switch that is going offline is the only server in the VTP
domain, then absolutely nothing happens to the domain as a whole. All of the
other client switches will hold their VLAN configs until another VTP server
comes along with a higher Configuration Revision number. If, however, there
are other VTP servers in the domain, then the VTP domain will function like
normal. When the offline switch comes back online, if any changes have been
made to the VTP domain then its Configuration Revision number will be lower
than everyone else and it will get updated.

Hope that helps.

Re: Clarification on VTP
Five switches are interconnected on a LAN which have multiple VLANs and are
all part of the same VTP domain.

Clarification One
How do we know from the information on "SWT - C" that which switches are
acting as or deployed as a Server of the VTP Domain.
-----
The command "show vtp status" will show your VTP server if you only have one
VTP server in your VTP domain.
I am not aware of any good way to determine all of the VTP servers of a VTP
domain.  I am not certian that there is a known way short of tracking the
VTP updates over time.  The last VTP server which provided an update will be
listed, but I do not believe that a complete list of all VTP servers in a
domain can be found without viewing all of the configuration commands of the
switches.
There are three VTP show commands on a common Cisco ethernet switch:
   Cisco6509#show vtp ?
     counters  VTP statistics
     password  VTP password
     status    VTP domain status

The output of "show vtp status" is included at the end of this message.
The output of "show vtp counters" is included at the end of this message.
There can be more than one VTP server in a VTP domain.  Recall the practice
test question about how a newly configured switch is added to the network
and LAN connectivity is lost because by default a switch is a VTP server?
This is an example of multiple VTP servers in a VTP domain.  VTP clients
listend to VTP messages while VTP servers both listen and source VTP
messages.  Multiple VTP servers can exist on a VTP domain.
Multiple VTP domains can overlap managing of the same VLANs.  In the
situation presented, switch SWT-A could be a server of VTP domain wally and
switch SWT-B could be a server of VTP domain world.  VTP domain wally has
VLANs 1, 2, and 3.  VTP domain world has VLANs 1, 2, and 5.  Switch SWT-C, a
client of VTP domain wally, has VLANs 1, 2, and 3.  Switch SWT-D, a client
of VTP domain world, has VLANs 1, 2, and 5.  When switch SWT-A of VTP domain
wally removes VLAN 3, switch SWT-C removes VLAN 3 while switches SWT-B and
SWT-D do nothing.  If all of these switches were part of the same VTP
domain, even with both SWT-A and SWT-B being servers, the removal of VLAN
information from one server will result in the removal of the VLAN from
other server and the clients.

Clarification Two
Suppose One "VTP Server Switch" is disconnected from the domain for 20
minutes and then reconnect again back, in the 20 minute period what happens
to the VLANS on the Domain as a whole.
-----
If the VTP server was removed from the network and then reconnected without
powering off, the VTP clients and their VLANs remain unaffected.
If the VTP server rejoins the network after a restart, its VTP update
revision number will be lower than the last update received by the clients.
Change a client to server mode, make a VLAN change, and then it change back
to client mode.  This will send a recent revision number update which the
actual VTP server will receive and continue from in its own updates.  From
that point on, the VTP updates from the real VTP server will match the next
expected revision of the VTP clients.



-----

Cisco6509#show vtp status
VTP Version                     : 2
Configuration Revision          : 11
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 25
VTP Operating Mode              : Server
VTP Domain Name                 : CiscoLAN
VTP Pruning Mode                : Enabled
VTP V2 Mode                     : Disabled
VTP Traps Generation            : Disabled
MD5 digest                      : 0x45 0x32 0xBC 0x9B 0xDB 0x43 0xED 0x6B
Configuration last modified by 192.168.1.150 at 6-6-06 7:06:00
Local updater ID is 192.168.1.20 on interface Vl1 (lowest numbered VLAN
interface found)

-----

Cisco6509#show vtp counters
VTP statistics:
Summary advertisements received    : 187562
Subset advertisements received     : 106
Request advertisements received    : 4
Summary advertisements transmitted : 265379
Subset advertisements transmitted  : 135
Request advertisements transmitted : 0
Number of config revision errors   : 0
Number of config digest errors     : 0
Number of V1 summary errors        : 0


VTP pruning statistics:

Trunk            Join Transmitted Join Received    Summary advts received
from
                                                   non-pruning-capable
device
---------------- ---------------- ---------------- ---------------------------
Gi1/1               1018856          1018843          0
Gi1/2               3690991          3690856          0
Gi1/3               996436           996413           0
Gi1/4              1019050          1019038          0
Gi1/5               3690961          0                0
Gi1/6              1018553          1018544          0

--

     ===========
     Scott Perry
     ===========
Indianapolis, Indiana
________________________________________
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Re: Clarification on VTP
Thanks Scott, Thanks Joseph. It is clear now.


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