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Re: Locking down Ports and DHCP
From: Bugbear <gbugbear () gmail com>
Date: Thu, 29 Jul 2010 09:04:08 -0400

First and foremost get your company policies and procedures in place
if you have not yet. Also, you will need "buy in" from the support
staff because their helpdesk calls are going to increase.

With that said, I would look at 802.1x

Assuming you are a Windows shop and your switches support it (most
modern switches do), take a look. I have leveraged it somewhat
successfully. I personally do not do any NAP/NAC (remediation), I just
very simply use Radius to auth the domain computers and domain users.
If joined to the domain and a member of this group then they are on
the production LAN, if not the switches will dynamically VLAN them to
a Quarantine VLAN.

What you do with "guests" is up to you from there. You can wait for
the helpdesk call or you could provide restricted internet access. If
the later, consider the appropriate egress filtering, logging,
alerting, IDS, etc... Also consider using PAT to give that network a
unique public IP. Lastly, consult your legal team to draw up some
language for "guests" to click through via Web Auth/Captive Portal
(most modern switches support this too). The language should note that
your Company is not responsible / liable and you hold the right to
monitor unencrypted traffic on the network (careful with what type of
monitoring - headers verse full content)

Most Printers, Scanner, AP's etc.. support 802.1x these days. An
alternative (not a very good one) would be port security via the mac
addr (but that will only keep the layman off).

Now the part your probably going to struggle with. The supplicant.
There are many. MS Windows XP SP3 and above has one built in and
supports GPO control. There are also products like Juniper/Odyssey and
Cisco Clean Access (Which i think just got EOL).

They all suck (excuse me have their limitations). The Windows
supplicant in Windows 7 seems to have been approved quite a bit
however. In XP there were issues with legit end users being temp
flipped to quarantine (while radius auth's them < the default
behavior). Once flipping back and the DHCP client will sometimes not
get an updated IP for that subnet. To date I have not found a
workaround, except Windows 7.

Also, if your admins are using logon scripts and not doing so through
GPO they will need to as they will not run post Auth

Other tech out there includes tracking/alerting after the fact
(someone being on your network).

Hope this helps

Tim



On Wed, Jul 28, 2010 at 5:36 PM, Tyler Robinson <pcimpressions () gmail com> wrote:
I am coming into an environment of over 1000 clients everything is setup
DHCP except printers and servers I am trying to work towards a much more
secure network but am at a loss of how to start locking down switches and
DHCP I want to make sure no one is plugging in unauthorized devices or rogue
devices for that matter so just wondering how everyone else is securing
there networks as always pauldotcom listeners are the best and all help is
welcomed.

TR

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