Which of the following statements best describes where a border router is normally placed?

A border router, also known as an edge router, functions as the primary gateway between an organization's internal network (an autonomous system) and an external network, such as the internet. In a standard, security-conscious network architecture, its logical placement is at the network perimeter. It receives traffic directly from the Internet Service Provider (ISP) and forwards it to the external firewall. The firewall then inspects and filters this traffic before it is allowed to proceed to the internal network or a Demilitarized Zone (DMZ). This layered approach establishes a critical security boundary.

A. This describes the placement of an internal firewall or a core network device, not the router at the network's edge.

B. A DNS server is an internal resource that should be protected behind the firewall, not placed in front of it.

C. This is incorrect because the firewall is a critical security component that must be placed between the border router and internal assets like a DNS server.

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1. National Institute of Standards and Technology (NIST). (2009). Special Publication 800-41 Revision 1: Guidelines on Firewalls and Firewall Policy.

In Section 3.2

"Firewall Topologies

" Figure 3-1 ("Simple Firewall with One DMZ") explicitly shows the network architecture where the external router is positioned between the Internet (i.e.

the ISP connection) and the firewall.

2. Cisco. (2015). SAFE Reference Guide.

The "Internet Edge Design" section and its associated diagrams (e.g.

Figure 10

"Internet Edge Design

" page 20) consistently depict the edge router as the device connecting to the ISP/WAN

which then connects to the Internet edge firewall. This architecture is presented as a best practice for securing the network perimeter.

3. Kurose

J. F.

& Ross

K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson.

This foundational textbook

widely used in university computer science programs

describes network architecture in Chapter 5. Section 5.6.3

"The Border Gateway Protocol (BGP)

" discusses the role of gateway routers (border routers) in connecting an organization's network (an Autonomous System) to the ISP's network

placing it at the very edge before other internal infrastructure like firewalls.