Subnetting and Configuration Speed Drills

0s15★ 35 XP

Lesson 167Interactive lesson

Subnetting and Configuration Speed Drills

A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.

Lesson format7 sections1 code block2 practice itemsUpdated Oct 2, 2026

bash

# Time yourself — 30 seconds per subnetting question

# 1. 10.10.10.75/26 — subnet and broadcast?
# Subnet: 10.10.10.64, Broadcast: 10.10.10.127

# 2. 172.16.20.150/25 — subnet and broadcast?
# Subnet: 172.16.20.128, Broadcast: 172.16.20.255

# 3. 192.168.10.200/29 — subnet and broadcast?
# Subnet: 192.168.10.200, Broadcast: 192.168.10.207

# 4. Subnet 10.0.0.0/8 into 500 subnets. What prefix?
# 2^9 = 512 subnets, so prefix = 8 + 9 = /17

# 5. What mask allows 200 hosts per subnet?
# 2^8 - 2 = 254 >= 200, so 8 host bits = /24 mask

# 6. 2001:db8::1/64 — network address?
# 2001:db8::/64

# 7. What is the CIDR notation for mask 255.255.254.0?
# /23

The exam doesn't give you a calculator. Every subnetting question happens in your head or on scratch paper. If you can't do these in under 30 seconds each, you'll lose time on the exam — time you need for the more complex questions. Build speed through repetition.

#The Fastest Mental Math#link

▪Memorize the CIDR-to-mask table: /24 = 255.255.255.0, /25 = .128, /26 = .192, /27 = .224, /28 = .240, /29 = .248, /30 = .252
▪Block size = 256 - last octet of mask. For /27, block = 256 - 224 = 32
▪Subnet boundaries: multiples of block size in the relevant octet
▪Broadcast = next subnet boundary - 1
▪Usable hosts = 2^(32-prefix) - 2
▪For subnetting questions, ask: what's the smallest block that fits the requirement?

★ 15 XPmedium

SYNTAX VALIDATION (★ 15 XP)

What is the broadcast address for 172.16.50.150/27?

root@vulnarex:~#

Press Enter to submit

★ 20 XPeasy

challenge BLOCK (★ 20 XP)

You need to assign IP 10.10.20.1/24 to Gi0/1 on a router and bring it up. Which sequence of commands is correct?

Select your proof vectors above

callout

Speed drills build the reflexes you need on the exam. Practice subnetting daily in the week before your exam — even 10 minutes a day. For CLI, run through the configs from Section 20's labs. By exam day, both should be automatic.

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The Fastest Mental Math

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October 2, 2026

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curl -H "Accept: text/markdown" "https://vulnarex.com/api/content/lessons?courseSlug=complete-ccna-200-301&lessonSlug=8-subnetting-configuration-speed-drills&lang=en&format=markdown"

MCP Server Config (mcp.json)

{
  "mcpServers": {
    "vulnarex": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-fetch"],
      "env": { "MCP_FETCH_URL": "https://vulnarex.com" }
    }
  }
}

MCP Server Card/.well-known/mcp.json A2A Agent Card/.well-known/agent-card.json API Catalog/.well-known/api-catalog robots.txt/robots.txt

Laboratory sanity code

Isolate active probes on matched virtual networks and keep execution streams sandboxed.

# Time yourself — 30 seconds per subnetting question

# 1. 10.10.10.75/26 — subnet and broadcast?

# Subnet: 10.10.10.64, Broadcast: 10.10.10.127

# 2. 172.16.20.150/25 — subnet and broadcast?

# Subnet: 172.16.20.128, Broadcast: 172.16.20.255

# 3. 192.168.10.200/29 — subnet and broadcast?

# Subnet: 192.168.10.200, Broadcast: 192.168.10.207

# 4. Subnet 10.0.0.0/8 into 500 subnets. What prefix?

# 2^9 = 512 subnets, so prefix = 8 + 9 = /17

# 5. What mask allows 200 hosts per subnet?

# 2^8 - 2 = 254 >= 200, so 8 host bits = /24 mask

# 6. 2001:db8::1/64 — network address?

# 2001:db8::/64

# 7. What is the CIDR notation for mask 255.255.254.0?

# /23