defense-in-depth using network virtualization and network admission control

© 2007 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1

Defense-in-Depth using Network Virtualization and Network Admission Control

Steven Carter – [email protected] Stewart – [email protected]


Agenda

Background/Overview

Network Virtualization Techniques

Network Access Control

Securing the Wild, Wild, West Q&A


Background

The term “Defense-in-Depth” refers to leveraging the defensive capability of every device in the network from the border of the network through the core, distribution, and access portions of the network and into the host itself.

This can be done by combining the following capabilities:– Firewall/IDS at the border to ward of threats before they enter the network

– Network virtualization to segregate the physical network into multiple virtual networks to support multiple security levels and services

– Network Access Control to authenticate user/hosts onto the network, check their security posture, and place them into the network that matches their requirements


Agenda

Background/Overview





Virtual Network

Internal

Network Virtualization Provide several networks to support varying security postures,

applications, etc.

One physical network supports many virtual networks

End-user perspective is that of being connected to a dedicated network (independent security policies, routing decisions, etc.)

Actual Physical Infrastructure

Visitor

Virtual Network Virtual Network

Voice


Network Device Virtualization

Switch Virtualization:– Data Plane – 802.1q VLANs– Control Plane – Per VLAN Spanning Tree


Network Device Virtualization (Cont.)

Router Virtualization:– Data Plane - Virtual Routing/Forwarding (VRFs)– Control Plane – Multiple instances of routing protocols (OSPF, EIGRP, etc) per routed plane.

802.1q, GRE, LSP,Physical Int, Others 802.1q or Others

Global

VRF

VRF


Data Path Virtualization

Tags:802.1q

Tunnels (connection oriented)GRE/mGRELabel Switched Paths—LSP (MPLS)

Multi-Hop Data Path Virtualization

IP

Single Hop Data Path Virtualization

802.1qTags Tags


Putting it Together

dsr02

Edge Network

Core Network

Distribution Network

VRF VRF

VRF VRF

Policy Enforcement Layer: Color Networks

Access/Building Network


Agenda

Background/Overview





Network Access Control (NAC)

NAC can mean different things to different people, but for the purposes of this presentation, it should provide three important functions:

– User/Host Authentication – The network should be able to authenticate the user (or at least the host) onto the network.

– Host Posture Verification – The ability to make sure that the host posture (virus definitions, patches, firewalls, etc.) match the policy of the network for which it is destined.

– Host Remediation – The placement of the host into the correct network

NAC provides that connection between Network Security and Host Security


Network Access Control (NAC) (Cont.)

Authenticate & Authorize Enforces authorization

policies and privileges

Supports multiple user roles

Update & Remediate Network-based tools

for vulnerability and threat remediation

Help-desk integration

Quarantine & Enforce Isolate non-compliant devices

from rest of network

MAC and IP-based quarantine effective at a per-user level

Scan & Evaluate Agent scan for required

versions of hotfixes, AV, etc

Network scan for virus and worm infections and port vulnerabilities

First, establish ACCESS POLICIES. Then:

LIMITED COMPLIANCE = LIMITED NETWORK ACCESS


What about the exceptions?

Hosts that do not support the mechanisms can be dealt with in various ways (external scanning, web authentication, etc.), but in general garner a lower level of trust and can be segregated from the general population

Because of their very nature, Research and Education networks have a number of hosts (upwards of 25%) that do not fit a supported configuration

There must be a credible option for these hosts, otherwise, you diminish much of the effect of implementing NAC in the first place


Addressing the Outliers

One option is to put a firewall in front of each and every host that cannot comply. This can be done with physical firewalls (i.e. a small firewall in front of every host):

– Pros - Straight-forward and easy for the policy people to understand and buy into; Depending on the situation, could be more cost-effective

– Cons – Logistically difficult and hard to administer; not scalable to large number


Addressing the Outliers (Cont.)

You can also do it (yes, you guessed it) VIRTUALLY

Difficult to do with a standard 802.1q VLANs because it is not scalable and difficult to avoid needing proper subset addresses per VLAN

Difficult to do with ACLs because of the shear number needed. Also not scalable and is difficult to maintain

Solution: Use sufficient security techniques to obviate the need for real firewalls


Agenda

Background/Overview





Securing the Wild, Wild, West

Overview:– Private VLANs to separate broadcast domains

– Port Security prevents MAC spoofing

– DHCP snooping prevents client attack on the switch and server

– Dynamic ARP Inspection adds security to ARP using DHCP snooping table

– IP Source Guard adds security to IP source address using DHCP snooping table


Securing the Wild, Wild, West (Cont.)

Private VLANs– PVLANs allow segregating broadcast segment into a non-broadcast multi-access-like segment.– Traffic that comes to a switch from a promiscuous port is able to go out on all the ports that belong to the same primary VLAN. – Traffic that comes to a switch from a port mapped to a secondary VLAN (it can be either an isolated, a community, or a two-way community VLAN) can be forwarded to a promiscuous port or a port belonging to the same community VLAN.

Distribution

Access

Secondary VLAN (isolated) Secondary VLAN (community)

Primary VLAN

Secondary VLANs


Securing the Wild, Wild, West (Cont.)

Port Security– Restrict a port's ingress traffic by limiting the MAC addresses that are allowed to send traffic into the port

– Number of address on the port is configurable

– Dynamically learned MAC address cuts down on administrative overhead

– “sticky” and non-”sticky” variants give the option of retaining learned address across port-down events

Only 1 MAC Only 1 MAC Address Address

Allowed on Allowed on the Port: the Port:

ShutdownShutdown


Securing the Wild, Wild, West (Cont.) DHCP Snooping

– Acts like a firewall between untrusted hosts and trusted DHCP servers– Validates and Rate-Limits DHCP messages received from untrusted sources and filters out invalid messages. – Builds and maintains the DHCP snooping binding database, which contains information about untrusted hosts with leased IP addresses to validate subsequent requests from untrusted hosts

DHCPServer

DHCP Responses

TrustedUntrusted

DHCP Snooping

Unauthorized DHCP Response

DHCP Requests


Securing the Wild, Wild, West (Cont.) Dynamic Arp Inspection

– Intercepts, logs, and discards ARP packets with invalid IP-to-MAC address bindings

– Valid ARP packets based upon DHCP snooping binding database or from user-configured ARP access control lists (ACLs)

– Configurable to drop ARP packets when either the IP address or the the MAC address in the body does not match the Ethernet header

DHCPServer

DHCP Responses

TrustedUntrusted

DHCP Snooping


DHCP Requests

I’m your GW: 10.1.1.1

Not by my binding

table


Securing the Wild, Wild, West (Cont.) IP Source Guard

– IP source guard prevents IP spoofing by allowing only the IP addresses that are obtained through DHCP snooping on a particular port.

–This process restricts the client IP traffic to those source IP addresses that are obtained from the DHCP server; any IP traffic with a source IP address other than that in the PACLs permit list is filtered out

DHCPServer

DHCP Responses

TrustedUntrusted

DHCP Snooping


DHCP Requests

I’m your GW: 10.1.1.1

Not by my Port ACL


The End

Questions? Comments? Criticisms?

For more information:

Steven Carter – [email protected] Stewart – [email protected]

defense-in-depth using network virtualization and network admission control

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