An ISP provided a company with a pre-configured modem and five public static IP addresses. Which of the following does the company's firewall require…

For a firewall, or any network device, to communicate with the internet, it requires two fundamental pieces of information for its external-facing (WAN) interface. First, it needs a unique public IP address to be identifiable on the internet; the scenario specifies the ISP provided static IPs for this purpose. Second, it needs a Default Gateway, which is the IP address of the next-hop router on the ISP's network. The firewall sends all traffic destined for non-local networks (i.e., the internet) to this gateway. These two components are the minimum requirements for establishing basic IP routing and internet access.

A. NTP server: An NTP server is used for time synchronization. While important for logging and security, it is not a prerequisite for establishing basic internet connectivity.

C. The modem's IP address: The firewall needs the IP address of the default gateway. While this might be the modem's IP in some configurations, "default gateway" is the correct and universally required configuration parameter.

E. DNS servers: DNS is required to resolve domain names to IP addresses. Basic internet access (e.g., connecting to a public IP) works without DNS; it is a service used over the internet, not a requirement for it.

F. DHCP server: DHCP is used for automatic IP address assignment. The scenario explicitly states the company was given static IP addresses, which require manual configuration.

1. Kurose

J. F.

& Ross

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

Section 4.4.2

"The Internet Control Message Protocol (ICMP)" and Section 5.2

"Routing Algorithms": These sections explain the core mechanics of IP routing. A host (or firewall) must have an IP address to be a source/destination and must know the address of its first-hop router (default gateway) to forward datagrams off its local subnet. The configuration of a default route is fundamental to this process.

2. Cisco. (2022). Configure a Static WAN IP Address on RV34x Series Routers. Cisco Technical Assistance Center (TAC).

"Configure Static IP" section

Step 4: The official configuration guide explicitly lists the mandatory fields for establishing a static WAN connection as "IP Address

" "Subnet Mask

" and "Default Gateway." This demonstrates the essential parameters required from a vendor's perspective.

3. Braden

R. (Ed.). (1989). Requirements for Internet Hosts -- Communication Layers. RFC 1122. Internet Engineering Task Force (IETF).

Section 3.3.1.1

"Simple-Minded Gateway Selection": This foundational document specifies the IP protocol stack requirements. It states

"When a host sends a datagram

it must make a routing decision... This decision is based upon a 'routing table'... There may be a 'default' route..." This establishes the default gateway as a core component of IP forwarding logic. (DOI: https://doi.org/10.17487/RFC1122)