CompTIA N10-009 - CompTIA Network+ Certification Exam

Understanding the Requirements

Network Address: 192.168.1.0/24

The /24 notation means a subnet mask of 255.255.255.0, providing 256 total addresses (192.168.1.0–192.168.1.255).

Usable hosts: 256 – 2 (network and broadcast) = 254.

Goal: Create 3 subnets, each with 30 hosts.

Each subnet needs enough addresses to accommodate 30 hosts, plus 2 reserved addresses (network and broadcast) per subnet.

Total addresses per subnet = 30 (hosts) + 2 (network/broadcast) = 32 addresses.

Subnetting Basics (Networking Fundamentals)

Subnet Mask: Determines how many bits are borrowed from the host portion to create subnets.

Original Mask: /24 (255.255.255.0) = 24 network bits, 8 host bits.

Formulae:

Number of subnets = 2^(number of borrowed bits).

Number of addresses per subnet = 2^(remaining host bits).

Usable hosts per subnet = 2^(remaining host bits) – 2.

We need:

At least 3 subnets.

At least 32 addresses per subnet (to fit 30 hosts + 2 reserved).

Step-by-Step Analysis

Determine Addresses Needed per Subnet:

32 addresses is a power of 2 (2^5 = 32).

This means each subnet requires 5 host bits (since 2^5 = 32 total addresses, and 32 – 2 = 30 usable hosts).

Calculate Remaining Bits:

Original network has 8 host bits (/24).

If 5 bits are left for hosts, we borrow: 8 – 5 = 3 bits for subnetting.

New Subnet Mask:

Original mask: /24 (24 network bits).

Borrow 3 bits: 24 + 3 = /27.

/27 = 255.255.255.224 (binary: 11111111.11111111.11111111.11100000).

Verify Requirements:

Number of Subnets: 2^3 = 8 subnets (meets the requirement of at least 3).

Addresses per Subnet: 2^5 = 32 addresses.

Usable Hosts per Subnet: 32 – 2 = 30 hosts (exactly meets the requirement).

Subnet Breakdown:

Increment: 256 – 224 = 32 (each subnet increments by 32 in the fourth octet).

Subnets:

192.168.1.0–192.168.1.31 (Network: .0, Broadcast: .31, Hosts: .1–.30)

192.168.1.32–192.168.1.63 (Network: .32, Broadcast: .63, Hosts: .33–.62)

192.168.1.64–192.168.1.95 (Network: .64, Broadcast: .95, Hosts: .65–.94)

(And 5 more subnets up to 192.168.1.255.)

Three subnets fit perfectly with 30 hosts each.

Evaluating the Options

A. 255.255.255.128 (/25):

Borrow 1 bit: 24 + 1 = /25.

Subnets: 2^1 = 2 (not enough, need 3).

Host bits: 7 (2^7 = 128 addresses, 126 hosts).

Why Not: Only 2 subnets, fails the requirement.

B. 255.255.255.192 (/26):

Borrow 2 bits: 24 + 2 = /26.

Subnets: 2^2 = 4 (meets 3).

Host bits: 6 (2^6 = 64 addresses, 62 hosts).

Why Not: 62 hosts exceeds 30, but it’s overkill; /27 is more efficient and still valid.

C. 255.255.255.224 (/27):

Borrow 3 bits: 24 + 3 = /27.

Subnets: 2^3 = 8 (meets 3).

Host bits: 5 (2^5 = 32 addresses, 30 hosts).

Why Yes: Perfectly fits 3 subnets with exactly 30 hosts each.

D. 255.255.255.240 (/28):

Borrow 4 bits: 24 + 4 = /28.

Subnets: 2^4 = 16 (meets 3).

Host bits: 4 (2^4 = 16 addresses, 14 hosts).

Why Not: Only 14 hosts per subnet, fails the 30-host requirement.

Why /27 (255.255.255.224) is Best

It provides exactly 30 usable hosts per subnet, avoiding waste while meeting the minimum requirement.

It allows 8 subnets, exceeding the need for 3, ensuring flexibility.

The study guide emphasizes efficient subnet design, and /27 balances host count and subnet availability.

CompTIA Network+ Context

Networking Fundamentals: Subnetting is a core skill, requiring understanding of CIDR, binary conversion, and address allocation.

Example from Study Guide: Similar problems calculate subnet masks for specific host counts, reinforcing /27 as a common solution for ~30 hosts.

Port 587 is used for secure email submission. This port is designated for message submission by mail clients to mail servers using the SMTP protocol, typically with STARTTLS for encryption.

Port 25: Traditionally used for SMTP relay, but not secure and often blocked by ISPs for outgoing mail due to spam concerns.

Port 110: Used for POP3 (Post Office Protocol version 3), not typically secured.

Port 143: Used for IMAP (Internet Message Access Protocol), which can be secured with STARTTLS or SSL/TLS.

Port 587: Specifically used for authenticated email submission (SMTP) with encryption, ensuring secure transmission of email from clients to servers.

Network References:

CompTIA Network+ N10-007 Official Certification Guide: Discusses email protocols and ports, including secure email transmission.

Cisco Networking Academy: Provides training on securing email communications and the use of appropriate ports.

Network+ Certification All-in-One Exam Guide: Explains email protocols, ports, and security considerations for email transmission.

In a mesh topology, every node is directly connected to every other node. This provides high redundancy and reliability, as there are multiple paths for data to travel between nodes. This topology is often used in networks where high availability is crucial.References: CompTIA Network+ study materials.

BGP (Border Gateway Protocol) is the only dynamic routing protocol used across the internet. It's classified as an Exterior Gateway Protocol (EGP), responsible for routing between different autonomous systems (ASes).

A. EIGRP and D. OSPF are Interior Gateway Protocols (IGPs), used within organizations.

C. RIP is an outdated IGP with limited use, unsuitable for internet-scale routing.

📘 Reference:

CompTIA Network+ N10-009 Official Objectives: 3.1 – Compare and contrast various routing technologies.

SSH (Secure Shell) is a cryptographic network protocol that enables secure remote management and operation of network devices, including routers and switches. SSH encrypts traffic, making it more secure than alternatives like Telnet, which sends data in plaintext. The document states:

“SSH (Secure Shell) is the recommended protocol for secure, interactive remote management of network devices. It provides a secure channel over an unsecured network by encrypting the traffic between the administrator’s workstation and the managed device.”

Understanding End-of-Support:

End-of-Support Status: When a vendor declares a device as end-of-support, it means the device will no longer receive updates, patches, or technical support. This poses a security risk as new vulnerabilities will not be addressed.

Risks of Keeping an End-of-Support Device:

Security Vulnerabilities: Without updates, the switch becomes susceptible to new security threats.

Compliance Issues: Many regulatory frameworks require that critical infrastructure be maintained with supported and secure hardware.

Best Next Step - Replacement:

Decommission and Replace: The most secure approach is to replace the end-of-support switch with a new, supported model. This ensures the infrastructure remains secure and compliant with current standards.

Planning and Execution: Plan for the replacement by evaluating the network's needs, selecting a suitable replacement switch, and scheduling downtime for the hardware swap.

Comparison with Other Options:

Apply the Latest Patches: While helpful, this does not address future vulnerabilities since no further patches will be provided.

Ensure the Current Firmware Has No Issues: This is only a temporary measure and does not mitigate future risks.

Isolate the Switch from the Network: Isolating the switch may disrupt network operations and is not a viable long-term solution.

To access the internet using static IPs, the firewall (or router) must be configured correctly:

B. Default gateway: This is essential because it tells the firewall where to send outbound traffic destined for outside the local network.

D. One static IP address: The firewall must be assigned one of the static IPs to communicate over the public internet.

The other options are not essential for basic internet connectivity in this context:

A. NTP server: Useful for time synchronization but not required for internet access.

C. The modem’s IP address: Irrelevant unless doing modem-level configuration.

E. DNS servers: Important for name resolution but not for basic layer 3 connectivity.

F. DHCP server: Not used when static IPs are assigned.

📘 Reference:

CompTIA Network+ N10-009 Official Objectives: 2.2 – Compare and contrast addressing technologies.

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A mesh network is the best solution for providing reliable wireless service to public safety vehicles. In a mesh network, each node (vehicle) can connect to multiple other nodes, providing multiple paths for data to travel. This enhances reliability and redundancy, ensuring continuous connectivity even if one or more nodes fail. Mesh networks are highly resilient and are well-suited for dynamic and mobile environments such as public safety operations.References: CompTIA Network+ study materials.