Problem while using VLAN

Hi,

I am trying to configure a few thousand (< 5000) VLAN devices on 2.5.70, and use following commands (in a loop) :

	vconfig add eth0 $i$j
	ifconfig eth0.$i$j 10.0.$i.$j broadcast <> netmask <> up
	ifconfig eth0.$i$j add fec0:1:2:$i::$j/64

I get following problems :
	1. After some time, I lose the link local and site local addresses on my eth0 and eth1 interfaces which were added through autoconfig.
	2. After some time, I lose link local and site addresses on all VLAN devices (after creating a few thousand devices).
	3. I find two devices for each created device, eg two eth0.232 or eth0.45 devices. So if I create 100 devices, I get 200.

Is there any reason for this to happen, and am I doing something wrong ? Alternatively, any fixes for this ?

Thanks,

- KK