VLAN database VTP management

[orthostaticindifference]

Hi guys, sorry to spam up the boards with the same basic CCNA level stuff, but I have a couple of questions about ios differences, limitations, and references. I have the following three switches. One appears to be considerably dated in regard to software version. My confusion/ignorance stems from managing VTP settings.

2924XL     12.0 5 WC8

2950          12.1 22 EA6

2950          12.1 22 EA6

When I set either 2950 switch as the VTP server, and the other as a client, the client inherits the server settings as expected. However the 2924 requires that I go into the vlan database from priv exec and manually set vtp client. That's pretty similar to setting any switch to client mode. The problem I am observing is that after setting the 2924 to client, it still doesn't inherit vtp version settings or pruning settings. I still have to manually configure those.

Additionally, if I copy run start the 2924 after making these manual settings, and then reload the switch, all the settings are lost and it defaults back to server mode with all features disabled. From my searches, it looks like vlan information is stored in vlan.dat, but all the documentation I've found is on 12.1 ios which doesn't appear to use vlan database for vtp setup, meaning it might still be an issue, but not one I'm focused on at the moment.

Is the vlan database dumped at reload? I've read vlan.dat is stored in nvram and should be saved after a copy run start, but that is not the case for me.

I have since set the 2924 as the server, manually configured the server from vlan database, executed copy run start, and reloaded the switch. Oddly, my manual settings saved from the reload, meaning I only lose settings when the switch is in client mode.

Am I missing additional necessary client commands to save the config, or is this just a limitation of either the 2924XL or the 12.0 ios?

On a related but completed out of scope topic, without a cisco service contract, how am I supposed to make heads or tails of all the different versions of ios, along with the letter-based features and what-not? I can't even find my 2924 in the list of platforms when searching for ios upgrades. I seem to be low tide on the failboat here. Thanks for any education you can provide!

[Alessio Andreoli · Accepted solution]

Hi John,

even if not configured, VTP does have authentication that can fail as much as other mechanisms. A checklist for VTp could be:

- keep in mind that the version must be the same even if the backward compatibility between version 2 and version 1 is there

- check the configuration revision number  (show vtp status) the server sending out the updates must have the highest value

- on the old version of IOS do not store the vlan database configuration with copy run start but with the apply command

sw# vlan data

sw#(vlan) vtp server

sw#(vlan)apply

sw#(vlan)exit

it should be stored in this way.

- VTP some times needs to be forced to an update to converge, create and delete a vlan for example.

having said this, you are not missing anything. VTP is a good solution but many experts do not believe it is worth the price you have to pay in administration overhead and control. Pruning is a good tool as the domain name features and so on but remember that VTP does not define and broadcast domain.

hope it helps

Alessio

[orthostaticindifference]

Alessio,

That is very helpful information. Fortunately at the moment (or unfortunately depending on how you look at it) I am not on a production networ, so I am not faced with the choice of using VTP or not, so right now I'm just making sure I know how to administer it. Thank you for chipping in on the value of VTP.

I am still a little stuck on client mode configuration. When I set the 2924 switch to client, and manually administer the settings, I am unable to use the apply command. Here is a snippet when I try to do that:

c2924(vlan)#vtp server

Device mode already VTP SERVER.

c2924(vlan)#vtp client

Setting device to VTP CLIENT mode.

c2924(vlan)#apply

Apply not allowed when device is in CLIENT state.

c2924(vlan)#

So does this simply mean that as a client, VTP settigns cannot be stored, and since the older IOS won't inherit the VTP server settings, that this either needs to be the server or manually configured each time?

[Alessio Andreoli]

Hi John,

this Apply command refer to all the possible changes that you could do. So, since you cannot do changes in client mode you should just type

sw(vlan)exit

this command will apply your changes and will go out from the vlan database configuration.

Hope this helps

Alessio

[orthostaticindifference]

Well, this is embarassing. After all of this work, and proofing stuff out, then running the reload, the issue I thought I was experiencing before is no longer happening. I have no idea now where my error was, but after setting all three switches to client mode, and then setting my primary 2950 to server, and then going through the manual settings as described in your post, and in my post below, the 2924 is retaining the settings.

The strange thing is I know I had this config before, and after a reload I lost the vlan database settings for the 2924. I couldn't have reloaded while in (vlan)# as that is unrecognized, so I had to exit and save the client config. Oh well. I'll just assume I didn't copy run start after exiting vlan database and reloaded.

Thank you for your help and responses. This did help me a lot. I've included info below to show it's working -- but you already expected that

Here I am setting a 2950 to be the VTP server:

2950(1)#conf t

Enter configuration commands, one per line.  End with CNTL/Z.

2950(1)(config)#vtp mode server

Setting device to VTP SERVER mode

2950(1)(config)#vtp pru

2950(1)(config)#vtp pruning

Pruning already switched on

2950(1)(config)#exit

2950(1)#copy run start

Destination filename [startup-config]?

Building configuration...

[OK]

2950(1)#

Here I have set my 2924 as a VTP client, and exited

c2924#vlan database

c2924(vlan)#vtp client

Device mode already VTP CLIENT.

c2924(vlan)#vtp v

c2924(vlan)#vtp v2-mode ?

c2924(vlan)#vtp v2-mode

V2 mode already enabled.

c2924(vlan)#exit

In CLIENT state, no apply attempted.

Exiting....

c2924#

Here is the VTP status of my server, the client 2950, and the client 2924:

2950(1)#sho vtp st

VTP Version                     : 2

Configuration Revision          : 4

Maximum VLANs supported locally : 64

Number of existing VLANs        : 5

VTP Operating Mode              : Server

VTP Domain Name                 : s1

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x46 0x10 0x68 0xB2 0x0E 0x20 0x72 0xBF

Configuration last modified by 192.168.1.131 at 3-1-93 11:56:43

Local updater ID is 192.168.1.131 on interface Vl1 (lowest numbered VLAN interface found)

2950(1)#

2950(2)#sho vtp st

VTP Version                     : 2

Configuration Revision          : 4

Maximum VLANs supported locally : 64

Number of existing VLANs        : 5

VTP Operating Mode              : Client

VTP Domain Name                 : s1

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x46 0x10 0x68 0xB2 0x0E 0x20 0x72 0xBF

Configuration last modified by 192.168.1.131 at 3-1-93 11:56:43

2950(2)#

c2924#sho vtp st

VTP Version                     : 2

Configuration Revision          : 1

Maximum VLANs supported locally : 68

Number of existing VLANs        : 5

VTP Operating Mode              : Client

VTP Domain Name                 :

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x30 0x8F 0x85 0xA2 0x57 0x7D 0xCF 0x7E

Configuration last modified by 192.168.1.133 at 3-1-93 00:29:51

c2924#

So, as you can see, they are all using version 2, and the two clients are clients as desired, after the vlan database manual config for the 2924 client.

Here is a show status on the 2924 after a reload.

VTP Version                     : 2

Configuration Revision          : 1

Maximum VLANs supported locally : 68

Number of existing VLANs        : 5

VTP Operating Mode              : Client

VTP Domain Name                 :

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x30 0x8F 0x85 0xA2 0x57 0x7D 0xCF 0x7E

Configuration last modified by 192.168.1.133 at 3-1-93 00:29:51

c2924#

[Alessio Andreoli]

Why embarassing?????? It's Cisco!!!!!

Good Luck

Alessio