Security Basics mailing list archives
RE: Firewall and VLAN security design
From: "Ivan Coric" <ivan.coric () workcoverqld com au>
Date: Thu, 04 Nov 2004 09:00:53 +1000
IMHO it's bad practice to segregate your trusted and untrusted networks with VLANs. Use one switch for the external net and DMZ if you must, but use a separate switch for your internal LAN. @Stake security review of VLANs http://www.cisco.com/warp/public/cc/pd/si/casi/ca6000/prodlit/vlnwp_wp.pdf VLAN Features http://www.cisco.com/univercd/cc/td/doc/product/lan/28201900/1928v8x/eescg8x/aleakyv.htm Layer 2 -- The Weakest Link http://www.cisco.com/en/US/about/ac123/ac114/ac173/ac222/about_cisco_packet_feature09186a0080142deb.html There have been threads on this issue previously on the list http://www.cotse.com/mailing-lists/bugtraq/1999/1397.html cheers Ivan Ivan Coric, CISSP IT Technical Security Officer Information Technology WorkCover Queensland Ph: (07) 30066414 Fax: (07) 30066424 Email: ivan.coric () workcoverqld com au
Jonathan Loh <kj6loh () yahoo com> 4/11/2004 8:17:16 am >>>
Actually, I think cisco does. It just depends on how you comprehend the following statement. Taken from the CCNA course curriculum Semester 3 module 8 overview. "VLANs can enhance scalability, security, and network management. Routers in VLAN topologies provide broadcast filtering, security, and traffic flow management." Strictly speaking "can enhance" does no mean the same as "does enhance". --- Ivan Coric <ivan.coric () workcoverqld com au> wrote:
I beg to differ, using VLANs to segregate your external and internal network is a bad idea. I don't think even Cisco recommends VLANs as a security mechanism http://www.sans.org/resources/idfaq/vlan.php http://www.spirit.com/Network/net0103.html http://www.terena.nl/conferences/tnc2003/programme/slides/s1c3.ppt http://www.sans.org/rr/whitepapers/networkdevs/1090.php
http://www.google.com.au/search?q=vlan+hopping&hl=en&lr=&start=10&sa=N
cheers Ivan Ivan Coric, CISSP IT Technical Security Officer Information Technology WorkCover Queensland Ph: (07) 30066414 Fax: (07) 30066424 Email: ivan.coric () workcoverqld com au"Bryan S. Sampsel" <bsampsel () libertyactivist org> 2/11/2004
2:56:11
pm >>>Is VLAN segmentation enough to segment between the internet, DMZandthe internal network, or should I also use different switches for each, and be connected through the firewall.This is a FAQ, and the usual answer is that no, VLAN separation
is
nota robust security barrier, an separate switches are recommended
where
thedifferent subnets need separation for security reasons.Actually, if you don't offer up your management interface to the publicly accessible side of things, the VLAN separation makes things function exactly like a physically separate switch. Without the routing between those VLANs, the traffic does not magically go from one VLAN to another and the ability to exploit/crack the switch is no greater than
having
a separate switch in place. In fact, if you have a managed switch,
and
do not logically isolate your management interface/IP, you're opening
up
that standalone switch. If you're not crazy enough to put the management IP on the publicly accessible side, there is no risk unless you allow access through a firewall or other routing solution. This is a fundamental concept
of
managed switches and VLANs. This is at least true of Foundry Networks and Cisco switches.
Mileage
may vary. ;) Sincerely, Bryan S. Sampsel LibertyActivist.org FNCNE
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Current thread:
- Firewall and VLAN security design Ahmed Ameen (Nov 01)
- RE: Firewall and VLAN security design David Gillett (Nov 01)
- RE: Firewall and VLAN security design Bryan S. Sampsel (Nov 02)
- RE: Firewall and VLAN security design David Gillett (Nov 03)
- RE: Firewall and VLAN security design Bryan S. Sampsel (Nov 02)
- <Possible follow-ups>
- RE: Firewall and VLAN security design Ivan Coric (Nov 03)
- RE: Firewall and VLAN security design Jonathan Loh (Nov 03)
- RE: Firewall and VLAN security design Paul Benedek (Nov 03)
- RE: Firewall and VLAN security design Bryan S. Sampsel (Nov 03)
- RE: Firewall and VLAN security design Ghaith Nasrawi (Nov 12)
- RE: Firewall and VLAN security design Ivan Coric (Nov 03)
- RE: Firewall and VLAN security design David Gillett (Nov 01)