Two quick VTP/Trunking questions...

SMR511

1] Where do VTP CLIENTS keep their vlan configs ?

Odom says in flash (vlan.dat) like vtp servers in the Official Guide.
Bryant says in running-config on the ICND2 Train Signal Vids.

???

2] Do 2960's default to "dynamic AUTO" and 2950's to "dynamic DESIRABLE" ?


Thanks for your help.

fly351

1) VTP Clients do not store the VLAN config in running config; that is Transparent mode.

2) I believe that is correct.

SMR511

Wow...Train Signal says


Server in NVRAM
Client in Running-Config
Transparent in NVRAM


(Around 1:35 in the Switching II video)


But it's actually ...

Server in NVRAM
Client in NVRAM
Transparent in Running-Config


The Odom book should take precedence I would assume. Just double checking.

SMR511

Actually Odom says transparent stores vlan config BOTH in the running-config and NVRAM.

Server and Client in NVRAM.


I'm going with that unless I hear otherwise.

fly351

Don't confuse NVRAM for the VLAN.DAT file. The running-config is stored in RAM. The start-up config is stored in NVRAM along with the VLAN.DAT file.

Transparent switches store the VLAN information in the startup config in NVRAM.

Client switches store the VLAN information in RAM; power lose / reload will make the client switch re-learn the VLANs from the server.

Server switches store the VLAN information in the VLAN.DAT file in NVRAM.

Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide, 12.1(19)EA1 - Configuring VTP [Cisco Catalyst 2950 Series Switches] - Cisco Systems

jojopramos

according to jeremy, VLAN config in server mode is save in VLAN database (vlan.dat). You can't save VLAN config in client mode. Transparent mode will be saved in NVRAM.

APA

fly and jojo are spot on

clients don't actually keep a copy of the database..... its knowledge of VLANs is only in running-memory.... hence on reboot it needs to relearn off the server...

The minute you turn a client into and transparent mode VTP switch the VLANs are then copied into the actual output of the running config... so upon next wr mem\copy run start they are saved to the startup-config.

Servers - obviously have the read\write copy of the VLAN database and therefore it is stored in NVRAM...

Just don't bring a client up with a higher revision then the server...otherwise kiss your database goodbye...

Netwurk

All 3 modes use the vlan.dat file, although transparent mode will ignore the file after it looks at it during startup.

More detail here


Managing vlan.dat in Cisco Catalyst Switches Running Cisco IOS Software - Cisco Systems

SMR511

Thanks guys, What you're saying makes sense to me but then is this wrong or am i missing something ?

This is pasted right out of the Odom ICND2 book (pg.20)

"Storing VLAN Configuration

...Interestingly, Cisco IOS stores the information in the VLAN database differently than for most other Cisco IOS configuration commands. When VTP clients and servers store VLAN configuration—specifically, the VLAN ID, VLAN name, and other VTP configuration settings—the configuration is stored in a file called vlan.dat in flash memory. (The filename is short for “VLAN database.”) Even more interesting is the fact that Cisco IOS does not put this VLAN configuration in the running-config file or the startup-config file...

The process of storing the VLAN configuration in flash in the vlan.dat file allows both clients and servers to dynamically learn about VLANs, and have the configuration automatically stored, therefore making both client and server prepared for their next reload. If the dynamically learned VLAN configuration was only added to the running config file, the campus LAN could be exposed to cases in which all switches lost power around the same time (easily accomplished with a single power source into the building), resulting in loss of all VLAN configuration. By automatically storing the configuration in the vlan.dat file in flash memory, each switch has at least a recent VLAN configuration database, and can then rely on VTP updates from other switches if any VLAN configuration has changed recently.

An interesting side effect of this process is that when you use a VTP client or server switch in a lab, and you want to remove all the configuration to start with a clean switch, you must issue more than the erase startup-config command. If you only erase the startup-config and reload the switch, the switch remembers all VLAN config and VTP configuration that
is instead stored in the vlan.dat file in flash. To remove those configuration details before reloading a switch, you would have to delete the vlan.dat file in flash with a command such as delete flash:vlan.dat.

Switches in transparent mode store VLAN configuration in both the running-config file as well as the vlan.dat file in flash. The running-config can be saved to the startup-config as well"

Netwurk

SMR511 wrote: »

Thanks guys, What you're saying makes sense to me but then is this wrong or am i missing something ?

This is pasted right out of the Odom ICND2 book (pg.20)

Looks perfect to me. What part concerns you?

SMR511

I can't reconcile these two sentences...


"clients don't actually keep a copy of the database..... its knowledge of VLANs is only in running-memory.... hence on reboot it needs to relearn off the server."


(Odom pg.20)
"When VTP clients and servers store VLAN configuration—specifically, the VLAN ID, VLAN name, and other VTP configuration settings—the configuration is stored in a file called vlan.dat in flash memory."

Netwurk

SMR511 wrote: »

I can't reconcile these two sentences...


"clients don't actually keep a copy of the database..... its knowledge of VLANs is only in running-memory.... hence on reboot it needs to relearn off the server."


(Odom pg.20)
"When VTP clients and servers store VLAN configuration—specifically, the VLAN ID, VLAN name, and other VTP configuration settings—the configuration is stored in a file called vlan.dat in flash memory."

He's telling you the data is only stored in RAM and that the switch would lose its VLAN database in case of a power failure. The data being stored in the vlan.dat file prevents this.

SMR511

Sorry, In all sincerity I must be burned...studying alot lately

You mean with the following sentence, Odom is telling me that VTP Clients keep VLAN data only in RAM ?

"When VTP clients and servers store VLAN configuration—specifically, the VLAN ID, VLAN name, and other VTP configuration settings—the configuration is stored in a file called vlan.dat in flash memory."

Netwurk

SMR511 wrote: »

Sorry, In all sincerity I must be burned...studying alot lately

You mean with the following sentence, Odom is telling me that VTP Clients keep VLAN data only in RAM ?

"When VTP clients and servers store VLAN configuration—specifically, the VLAN ID, VLAN name, and other VTP configuration settings—the configuration is stored in a file called vlan.dat in flash memory."

He's telling you that it's stored in RAM and the vlan.dat file.

SMR511

In RAM but not the running-config ?


"Even more interesting is the fact that Cisco IOS does not put this VLAN configuration in the running-config file or the startup-config file"

Netwurk

SMR511 wrote: »

In RAM but not the running-config ?


"Even more interesting is the fact that Cisco IOS does not put this VLAN configuration in the running-config file or the startup-config file"

For client /server, the data is in RAM and the vlan.dat file, not in running-config