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Re: Locking down Ports and DHCP
From: "Butturini, Russell" <Russell.Butturini () Healthways com>
Date: Thu, 5 Aug 2010 15:49:23 -0500

We don't enable 802.1x on server switchports.  That stuff is in the datacenter or another secured area where people 
can't exactly unplug it and plug in without us knowing :-)

-----Original Message-----
From: pauldotcom-bounces () mail pauldotcom com [mailto:pauldotcom-bounces () mail pauldotcom com] On Behalf Of Dahl, 
Kevin
Sent: Thursday, August 05, 2010 1:26 PM
To: PaulDotCom Security Weekly Mailing List
Subject: Re: [Pauldotcom] Locking down Ports and DHCP

How do those of you who are using 802.1x solve the problem with patching and/or nightly backups ??

K-Dee


-----Original Message-----
From: pauldotcom-bounces () mail pauldotcom com
[mailto:pauldotcom-bounces () mail pauldotcom com] On Behalf Of Jody & Jennifer McCluggage
Sent: Thursday, July 29, 2010 8:00 PM
To: 'PaulDotCom Security Weekly Mailing List'
Subject: Re: [Pauldotcom] Locking down Ports and DHCP

I agree with Tim about recommending  802.1x.  You can set it up so that the switches will not allow access until the 
end-user authenticates themselves on the network (via Windows RADIUS service, IAS, communicating with a domain 
controller).  The 8021.X clients on Windows XP SP3 and higher are pretty stable (it will work on lower versions but
SP3 added some 802.1x improvements). As Tim pointed out, more and more embedded devices such as printers are now also 
supporting 802.1x.  For other embedded devices (older printers, copiers, UPS,  etc), you can utilize MAC address 
filtering.  This is less of an issue with these since they tend to be fairly static (i.e.
they won't be moving around much) and usually have some additional compensating physical controls.  You will probably 
want to use MAC Address filtering with your servers too. 802.1x tends not to work well with servers since it requires 
authentication prior to granting port access.  If someone has physical access to the ports that your servers are using, 
port
authentication is the least of your problems!     

Also as Tim said, keep in mind that you are adding some additional moving parts so more things can go wrong (8021.x 
client issues, switch issues, or RADIUS server issues - over the years I have had to deal with all three at one time or 
another but nothing real major).  That being said, except for the occasional minor headache,  I have had very little 
issues with it over the years. Also keep in mind that the workstation will not have access to the network until the 
user authenticates with an approved domain level account.  

Let me know If you want some examples on how to set up using Cisco switches and Windows workstations and radius/domain 
server.

Jody

  

-----Original Message-----
From: pauldotcom-bounces () mail pauldotcom com
[mailto:pauldotcom-bounces () mail pauldotcom com] On Behalf Of Bugbear
Sent: Thursday, July 29, 2010 9:04 AM
To: PaulDotCom Security Weekly Mailing List
Subject: Re: [Pauldotcom] Locking down Ports and DHCP

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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