[nsp] VLAN database propagation

[Vincent De Keyzer]

Hello,
 
a very VLAN basic question: what makes VLAN databases to be propagated (or
not) between two switches?
 
I have 3 switches with a seemingly similar config; VLAN database changes are
propagated from switch A to switch B (and vice-versa) but not to switch C...
 
Switch A: IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version
12.0(5.3)WC(1), MAINTENANCE INTERIM SOFTWARE
Switch B: IOS (tm) C2900XL Software (C2900XL-C3H2S-M), Version 12.0(5)XU,
RELEASE SOFTWARE (fc1)
Switch C: IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version
12.0(5.4)WC(1), MAINTENANCE INTERIM SOFTWARE

Vincent