VLAN security

[LINKCRAFT <linkcraft () yahoo com sg>]

I have a leased line network with few VLAN configured,
may I know how can I implement the security in order
to prevent hacking from one VLAN to another VLAN or
from internet. There is no firewall installed in the
network. Can I implement firewall? If affirmative, how
can I protect between each VLAN? They don't have to
access to each other. Or should I use IDS or any other
tools? Is there any freeware available?
Thanks/regards

=====

Thanks/regards 
Tan Yew Kwee

Linkcraft Supply & Services 
HP: 96959406 
Fax: 67814648


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