Enterasys Networks 9034385 - Manual (Page 60)

Survey the Network
4-8 Design Planning
authenticated to the network and interact with Enterasys NAC for authentication, assessment,
authorization, and remediation. Note however, that this configuration may not be possible if
trusted users are also being MAC authenticated to the network in the same Security Domain.
In this case, MAC or user overrides would need to be configured for the trusted users, and the
default NAC configuration of the Security Domain would specify the NAC implementation
for guest users.
• If guest access is implemented with web‐based authentication using the guest networking
feature on Enterasys policy‐capable switches (supplying default credentials in the web login
page for guest users), the guest networking feature must be configured to send the default
credentials to a backend RADIUS server and not locally authenticate them. This is because in
the out‐of‐band NAC configuration, the NAC Gateway must receive the authentication
attempt via RADIUS in order to detect the connecting end‐systems. A RADIUS server with the
guest networking credentials must be deployed on the network so the NAC Gateway can
proxy the RADIUS requests to the upstream RADIUS server. If a RADIUS Filter‐ID or VLAN
Tunnel attribute is not configured for the guest networking credentials on the upstream
RADIUS server, Enterasys NAC can be configured to include a Filter‐ID or VLAN Tunnel
attribute in the RADIUS Access‐Accept packet returned to the switch by implementing a user
override for the guest networking username.
3. Identify the Strategic Point for End-System Authorization
In this step, you will identify the strategic point in the network where end‐system authorization
should be implemented.
The most secure place for implementing authorization is directly at the point of connection at the
edge of the network, as supported by Enterasys policy‐capable switches. In this configuration, the
implementation of out‐of‐band NAC using the NAC Gateway appliance leverages policy on
Enterasys switches to securely authorize connecting end‐systems.
RFC 3580‐capable switches can be used for authentication and authorization by assigning end‐
systems to particular VLANs based on the authentication and assessment results. However, this is
not as secure as using Enterasys policy‐capable switches, for the two following reasons:
• VLANs authorize end‐systems by placing them into the same container, with the traffic
enforcement point implemented at the ingress/egress point to the VLAN on the VLANʹs
routed interface. Because authorization is not implemented between end‐systems within the
same VLAN, an end‐system in a VLAN is open to launch attacks or be attacked by other
devices within the same VLAN. For example, if end‐system A with virus X and end‐system B
with virus Y are quarantined into the same VLAN, then end‐system A and B may become
infected with virus X and Y. Enterasys policy uniquely authorizes connecting end‐systems
independent of their VLAN assignment by permitting, denying, and prioritizing traffic on
ingress to the network at the port level.
• Because RFC 3580‐capable switches implement the traffic enforcement point for a VLAN at
the VLAN’s routed interface, malicious traffic is allowed onto the network and may consume
bandwidth, memory, and CPU cycles on infrastructure devices before being discarded
possibly several hops deep within the network. This is especially detrimental to the operation
of the network if a single inter‐switch link connecting the access layer to distribution layer is
used to transmit traffic from both the quarantine VLAN and the production VLAN (such as an
802.1Q VLAN trunked link). Traffic from quarantined end‐systems (for example, worms
scanning for vulnerable hosts) can consume the entire bandwidth available on the inter‐switch
link and affect network connectivity for end‐systems on the production VLAN. In contrast,
since the traffic enforcement point for Enterasys policy is at the port of connection, malicious
traffic never ingresses the network to cause any disruption to network connectivity.