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Router Security Configuration Guide
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Version 1.0g
3.4. Security Policy for Routers
Routers are an important part of a network, and their security is a vital part of the
overall security for the networks they serve. What does it mean for a router to be
secure? One simple way to define the security of a router is this: do the operation,
configuration, and management of the router satisfy a good security policy?
3.4.1. A Conceptual Basis for Router Security Policy
Figure 3, below, shows a layered view of the security of a router. The security of
each layer depends on the security of the layers inside it.
Figure 3-4: Layered View of Router Security
The innermost zone is the physical security of the router. Any router can be
compromised by an attacker with full physical access; therefore, physical access must
be limited to provide a solid foundation for the overall security of the router. Most
routers offer one or more direct connections, usually called Console or Control
ports; these ports usually provide special mechanisms for controlling the router.
Router security policy should define rules for where and how these ports may be
used.
The next innermost zone of the diagram is the stored software and configuration state
of the router itself. If an attacker can compromise either of these, particularly the
stored configuration, then they will also gain control of the outer two layers. Some
important aspects of the stored configuration are the interface addresses, the user
names and passwords, and the access controls for direct access to the routers
command interface. Security policy usually includes strict rules about access to this
layer, in terms of both administrative roles and network mechanisms.
The next outermost zone of the diagram is the dynamic configuration of the router.
The route tables themselves are the most obvious part of this. Other pieces of
Network Traffic through the Router
Dynamic Configuration
and Status of the Router
Core Static Configuration
of the Router
Physical Integrity
of the Router
Router Security
Layers
Corresponding Access
Physical access
Electrical access
Administrative access
Software updates
Routing protocols
Access to the network that
the router serves