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VTP or VLAN.DAT strange behaviour


Sorry for this newbie question , but in my small CCNA LAB I have :

CISCO 1841 (with 4 ethernet por module to be able to use VTP in this router) + CISCO 2940

From one of the optional module in the CISCO 1841 I go with a trunck to the CISCO 2940.

The CISCO 1841 is VTP SERVER and the CISCO 2940 is CLIENT.

When I create in the CISCO 1841 the VLAN DATABASE of the 3 VLAN's :

VLAN 1 name VLAN1

VLAN 2 name VLAN2

VLAN 10 name VLAN10

After WR ; copy run  start ; reload  everithing work fine in my small ROUTER on a STICK demo.

So I am sure that VTP is working and that the Password and Domain are correct in both products.

BUT ......

If I switch OFF the Power of BOTH (Switch & Router) the VLAN 2 and 10 are gone. In other word the system use a default VLAN.DAT or create a NEW empty database !!!

When I compare the VLAN.DAT before and after the a power down I can see that before it is or has 1124 BYTES and after 740 BYTES.

Before I recycle the Power ON / OFF I made a Back-Up of the VLAN.DAT to VLAN.BAK. To make it work again I just have to copy bak VLAN.BAK to VLAN.DAT ; reload and everithing work again.

Why is the ROUTER creating a new empty DATABASE ?

To solve the problem I have set both ROUTER and SWITCH in TRANSPARANT mode and now it works , but I was wondering why this happens.

Thanks to this small lab I learned that their is a BIG difference between RELOAD and a power recycle.

The above is not a real case so it is not urgent , I just prepare my self for my CCNA in october

Best Regards,




Just for your information , I solved the problem by creating the VLAN's in the CONFIG TERMINAL and NOT in the VLAN DATABASE.

In a other 2621XM ROUTER when I create something in the VLAN DATABASE , it will show it in the SCRIPT , here in the 1841 it do not show.

My idea is that when I do a reload he use the VLAN DATABASE and when I restart , he write a empty VLAN DATABASE and use this empty database, this was why I coud see that the VLAN.DAT was always created at the time and day from the reboot.

I hope this information will be usefull for some people.

PS: The IOS from the CISCO1841 is 12.4(13r)T , the IOS on the CISCO2621XM is 12.4(24)T.

Best Regards,