Firewall Placement Question

[jason () tacorp com]

I would like to hear some thoughts on the placement of a firewall.  My 
intent isn't to start a flame but to debate the usefulness of two 
technologies inside the network firewall vs. IPS's.

The network which I manage is a university network that hasn't been looked 
after very well with regards to security and access control.  Right now 
there is a head end firewall that's 'inverted' as we say - that is we 
allow everything and just block a few things.

Between buildings we block a few ports on the l3 switches to 'contain 
outbreaks'.

There are three major problems which we are trying to address separetely.

1.  The Residence Halls are on the inside of the network.  They are coming 
off this summer.

2.  Wireless users are on the inside of the network.  We are building a 
'guest wireless' system that will be live this summer as well.

3. There are open network jacks all around campus and no kind of NAC in 
place.  This isn't being addressed yet.

Also being a university we have a hard time trusting our users and 
enforcing anti-virus installations and patching.

Recently there has been a push to install a transparent firewall in front 
of the server farm.  This is being done using a context on our firewall 
services module that protects (be it poorly) the border at the internet. 
However both the server network and internet border are being scanned by 
an IPS.

The question is: given that we are working to take historically abusive 
users off the network, is it really worth the time to install a firewall 
in front of the servers or just use the IPS?

I wonder about the labor required to pull this off for almost 200 servers 
(and Microsoft applications are a bitch).  I fear it will be hell to 
manage all the excpetions, ie. one user in a different building needs 
access to a few administrative ports.  Not to mention that after it's done 
we'll spend days trying to work out the bugs of things that 'should just 
work' and effects of application upgrades that change ports.

Lastly, is anyone doing any kind of filtering inside the network or is 
only done at the border?

Thoughts?

Regards,
Jason Mishka
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