VTP transparent mode question

mobri09

I know transparent mode still forwards advertisements, but it will not add anything to the its config. I was just wondering if it updates it's revision number.

r_durant

I think in transparent mode, the revision number will only change if you make changes on the switch that is in transparent mode, for instance if you have to add another VLAN...the revision number will not be updated from other switches in server mode, as you mentioned...it forwards the adverts.

shednik

mobri09 wrote:

I know transparent mode still forwards advertisements, but it will not add anything to the its config. I was just wondering if it updates it's revision number.

i believe r_durant is correct unless you make some type of change in the vlan configs the revision number should not change.

tech-airman

mobri09 wrote:

I know transparent mode still forwards advertisements, but it will not add anything to the its config. I was just wondering if it updates it's revision number.

mobri09,

According to Cisco, ...

Understanding VLAN Trunk Protocol (VTP) - Cisco Systems wrote:

Configuration Revision Number

The configuration revision number is a 32-bit number that indicates the level of revision for a VTP packet. Each VTP device tracks the VTP configuration revision number that is assigned to it. Most of the VTP packets contain the VTP configuration revision number of the sender.

Based on this, I would imagine that a VTP Transparent switch would update it's own internal revision number if VLANs are either created or deleted on the VTP transparent switch. However,...

Understanding VLAN Trunk Protocol (VTP) - Cisco Systems wrote:

VTP Modes
You can configure a switch to operate in any one of these VTP modes:
<snip>
Transparent—VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements, but transparent switches do forward VTP advertisements that they receive out their trunk ports in VTP Version 2.

So since a VTP transparent switch just relays VTP packets WITHOUT being configured by it, the VTP Transparent switch retains it's own revision number which may be different from the revision number in the VTP packet that it is relaying from the VTP server switche(s) to the VTP client switches. Similarly, since the VTP transparent switch doesn't SEND VTP packets, then any downstream VTP client switches shouldn't be affected by the VTP revision number on the VTP transparent switch.

I hope this helps.

Source:

1. Understanding VLAN Trunk Protocol (VTP) - Cisco Systems - http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml

mobri09

gotcha. I think the revision number for VTP transparent mode is always 0 anywho...so that makes sense

mwgood

Yes, revision number is always zero in transparent mode.

For example,

VTP Version : 2
Configuration Revision : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs : 24
VTP Operating Mode : Transparent

dtlokee

Just to add one more thing, a switch in VTP transparent mode using VTP version 1 will only forward advertisements from switches in VTP client or VTP server if the domain name of the transparent switch is the same as the advertisement. In VTP version 2 the switch will forward the advertisement regardless of the domain name.