✅ What is Subnetting?
Subnetting means dividing a large network (IP network) into smaller networks (subnets).
It helps in better management, security, and efficient use of IP addresses.
⭐ 1. Basic Terms
🔹 IP Address
- A unique address given to every device in a network.
- Example: 192.168.10.5
🔹 IPv4 Format
- IPv4 is a 32-bit address.
- Written in 4 octets (each 0–255).
Example: 192.168.1.10
🔹 Network Part & Host Part
Every IP has two parts:
| Part | Meaning |
|---|---|
| Network Part | Identifies the network |
| Host Part | Identifies a device inside the network |
Subnetting helps us change how many bits belong to network and host.
⭐ 2. Why is Subnetting Needed?
Subnetting is required to:
✔ Avoid wastage of IP addresses
If a network needs only 20 devices but you have 254 available addresses → waste.
Subnetting solves this.
✔ Improve security
Different departments can have separate subnets.
✔ Reduce network congestion
Smaller networks → fewer broadcasts → faster network.
✔ Better control & organization
Banks use subnetting heavily in branches, ATMs, servers, LAN networks, etc.
⭐ 3. Subnet Mask
A Subnet Mask decides how many bits are for network and how many for host.
Example:
- 255.255.255.0 = /24
- 255.255.255.128 = /25
- 255.255.255.192 = /26
- 255.255.255.224 = /27
Meaning of /24
- Network bits: 24
- Host bits: 8
- Possible hosts: 2⁸ – 2 = 254
⭐ 4. CIDR Notation
CIDR = Classless Inter-Domain Routing
Example:
- 192.168.1.0/24
- 10.0.0.0/16
The number after / tells how many bits are network bits.
⭐ 5. Subnetting Formula
To calculate number of hosts:
👉 Hosts per subnet = 2^(host bits) – 2
(We subtract 2 for Network ID + Broadcast ID)
👉 Number of subnets = 2^(borrowed bits)
Borrowed bits = extra bits taken from host part to create subnets.
⭐ 6. Subnetting Example
✔ Example 1
Given: 192.168.1.0/24
You want 2 subnets
Step 1: Find number of bits to borrow
2 subnets → 1 bit not enough (2¹ = 2) → OK
Borrow 1 bit
Step 2: New mask
Old: /24
New: /25
Step 3: Subnets created
Block size = 256 – 128 = 128
| Subnet | Network ID | Range | Broadcast |
|---|---|---|---|
| 1 | 192.168.1.0 | 1–126 | 192.168.1.127 |
| 2 | 192.168.1.128 | 129–254 | 192.168.1.255 |
⭐ 7. Shortcut Table for Subnet Masks
| Subnet Mask | CIDR | Hosts per Subnet |
|---|---|---|
| 255.255.255.0 | /24 | 254 |
| 255.255.255.128 | /25 | 126 |
| 255.255.255.192 | /26 | 62 |
| 255.255.255.224 | /27 | 30 |
| 255.255.255.240 | /28 | 14 |
| 255.255.255.248 | /29 | 6 |
| 255.255.255.252 | /30 | 2 |
⭐ 8. Important IP Terms
🟦 Network ID
The first IP address of the subnet.
🟦 Broadcast Address
The last IP address used to send messages to all devices in the subnet.
🟦 Usable Host Range
All addresses between Network ID and Broadcast ID.
⭐ 9. Subnetting
Banks use subnetting for:
- Branch Networks
- ATM Networks
- Core Banking Servers
- LAN inside banks
- VPN and secure networks
- Firewall configurations
Example:
ATMs may be given a separate subnet like 10.10.10.0/28 (14 hosts).
⭐ 10. Supernetting (Opposite of Subnetting)
Supernetting = combining multiple small networks into one large network.
Used by ISPs for routing efficiency.
Example:
- Combine:
192.168.0.0/24
192.168.1.0/24
Supernet = 192.168.0.0/23
⭐ 11. Common Points
- IPv4 = 32-bit
- Subnetting divides a network into smaller networks
- Subnet mask /24 = 255.255.255.0
- Hosts formula = 2^h – 2
- Broadcast address = last address
- CIDR stands for Classless Inter-Domain Routing
- Supernetting = Aggregation of networks
⭐ 12. MCQ
1–10: Basic definitions & fundamentals
- What is Subnetting?
A. Combining networks into one large network
B. Dividing a large network into smaller networks
C. Converting IPv4 to IPv6
D. Encrypting network data
Answer: B — Subnetting splits a network into smaller sub-networks. - IPv4 address length is:
A. 16 bits
B. 32 bits
C. 64 bits
D. 128 bits
Answer: B — IPv4 is 32 bits. - Which of the following is a correct classful default mask for Class C?
A. 255.0.0.0
B. 255.255.0.0
C. 255.255.255.0
D. 255.255.255.128
Answer: C — Class C default mask is 255.255.255.0 (/24). - CIDR notation 192.168.1.0/26 indicates how many host bits?
A. 6
B. 8
C. 26
D. 32
Answer: A — /26 means 26 network bits; host bits = 32 − 26 = 6. - Hosts per subnet formula is:
A. 2^(network bits) − 2
B. 2^(host bits) − 2
C. 2^(host bits) + 2
D. 2^(network bits) + 2
Answer: B — usable hosts = 2^(host bits) − 2 (network & broadcast excluded). - Subnet mask 255.255.255.192 corresponds to:
A. /24
B. /25
C. /26
D. /27
Answer: C — 255.255.255.192 = /26. - Which address in a subnet cannot be assigned to a host?
A. Any address ending with .1
B. Network ID and Broadcast address
C. Any address in the subnet
D. Gateway address only
Answer: B — first (network) and last (broadcast) addresses are reserved. - Broadcast address is used to:
A. Send to one host only
B. Send to all hosts in subnet
C. Encrypt network traffic
D. Replace subnet mask
Answer: B — broadcast sends to all hosts in the subnet. - Which one is a private IP address?
A. 8.8.8.8
B. 192.168.0.1
C. 203.0.113.1
D. 4.2.2.2
Answer: B — 192.168.0.0/16 is private. - What does CIDR stand for?
A. Classful Internet Domain Routing
B. Classless Inter-Domain Routing
C. Central Internet Data Routing
D. Classless Internal Domain Routing
Answer: B — CIDR = Classless Inter-Domain Routing.
11–20: Subnet mask & hosts calculations
- How many usable hosts are in a /29 subnet?
A. 2
B. 6
C. 14
D. 30
Answer: B — /29 ⇒ host bits 3 ⇒ 2^3 − 2 = 6. - A /30 subnet provides how many usable IP addresses?
A. 0
B. 1
C. 2
D. 4
Answer: C — /30 ⇒ host bits 2 ⇒ 2^2 − 2 = 2 (often used for point-to-point links). - Number of hosts in 255.255.255.128 subnet is:
A. 254
B. 126
C. 62
D. 30
Answer: B — 255.255.255.128 = /25 ⇒ 7 host bits ⇒ 2^7 − 2 = 126. - How many subnets are created if you borrow 3 bits from host portion?
A. 3
B. 6
C. 8
D. 16
Answer: C — borrowed bits = 3 ⇒ 2^3 = 8 subnets. - Given network 10.0.0.0/8, you need at least 1000 hosts per subnet. What is the smallest subnet mask you can use?
A. /22
B. /23
C. /24
D. /21
Answer: A — host bits needed: 2^10=1024 ⇒ host bits=10 ⇒ mask = 32−10 = /22. - Which mask gives 62 usable hosts?
A. /25
B. /26
C. /27
D. /28
Answer: B — /26 ⇒ host bits 6 ⇒ 2^6 − 2 = 62. - If network is 192.168.10.0/27, how many usable IPs?
A. 30
B. 62
C. 14
D. 254
Answer: A — /27 ⇒ host bits 5 ⇒ 2^5 − 2 = 30. - Block size (increment) for /26 subnet in last octet is:
A. 1
B. 2
C. 64
D. 192
Answer: C — /26 mask = 255.255.255.192 ⇒ increment = 256 − 192 = 64. - Network 172.16.0.0/20. What is the size (hosts per subnet)?
A. 4094
B. 2046
C. 1022
D. 254
Answer: B — /20 ⇒ host bits =12 ⇒ 2^12 − 2 = 4094. Wait check: 32−20=12 → 4096 −2 = 4094. Correct answer A.
Correction: Answer: A — 4094 usable hosts (2^12 − 2). - Which of the following masks is equal to /28?
A. 255.255.255.0
B. 255.255.255.240
C. 255.255.255.252
D. 255.255.255.128
Answer: B — 255.255.255.240 = /28.
21–30: Subnet identification & ranges
- What is the broadcast address of 192.168.1.64/26?
A. 192.168.1.127
B. 192.168.1.63
C. 192.168.1.191
D. 192.168.1.255
Answer: A — /26 block size 64; subnet 64–127 → broadcast = .127. - Network ID of IP 10.10.5.25 with mask 255.255.255.0 is:
A. 10.10.5.0
B. 10.10.0.0
C. 10.10.5.255
D. 10.10.5.1
Answer: A — /24 mask → network is 10.10.5.0. - Given IP 192.168.1.70/26, the subnet range is:
A. .0–.63
B. .64–.127
C. .128–.191
D. .192–.255
Answer: B — .64–.127 is the /26 range containing .70. - If an IP is 192.168.100.130 with /25 mask, which subnet does it belong to?
A. 192.168.100.0/25
B. 192.168.100.128/25
C. 192.168.100.64/25
D. 192.168.100.192/25
Answer: B — /25 splits at 0 and 128; 130 is in 128–255 subnet. - For 172.16.10.45/28, usable host range is:
A. .32–.47 (usable .33–.46)
B. .16–.31 (usable .17–.30)
C. .48–.63 (usable .49–.62)
D. .0–.15 (usable .1–.14)
Answer: A — /28 blocks of 16; 32–47 is correct range; usable .33–.46. - Which increment (subnet jump) is used for /27?
A. 8
B. 16
C. 32
D. 64
Answer: C — /27 mask = 255.255.255.224 ⇒ increment = 32. - Network 10.0.0.0/30: how many hosts and usable addresses?
A. 4 hosts, 2 usable
B. 2 hosts, 0 usable
C. 256 hosts, 254 usable
D. 8 hosts, 6 usable
Answer: A — /30 gives 4 addresses total; usable = 2. - Which of these is the correct network ID for 192.168.0.10/29?
A. 192.168.0.8
B. 192.168.0.0
C. 192.168.0.16
D. 192.168.0.32
Answer: A — /29 block size 8; 8–15 contains .10 → network ID .8. - IP 203.0.113.5 with mask 255.255.255.252 → network ID is:
A. .0
B. .4
C. .8
D. .252
Answer: B — /30 (mask .252) block size 4; .4–.7 contains .5 → network ID .4. - For 192.168.5.200/26, which is network ID?
A. 192.168.5.192
B. 192.168.5.128
C. 192.168.5.64
D. 192.168.5.0
Answer: A — /26 blocks: 0,64,128,192; .200 lies in 192–255 → network .192.
31–40: Concepts, special topics & best practices
- What is VLSM?
A. Very Large Subnet Mask
B. Variable Length Subnet Masking
C. Virtual LAN Standard Model
D. Versioned Local Subnetting Mechanism
Answer: B — VLSM allows different subnet mask sizes within the same network. - Which technique allows summarizing multiple networks into one route?
A. Subnetting
B. Supernetting (Route aggregation)
C. NAT
D. DHCP
Answer: B — Supernetting (route summarization) aggregates prefixes. - Which is true about subnet-zero?
A. It is always unusable
B. It is the first subnet (all zeroes) and is usable in modern networks
C. It is the broadcast address
D. It is only for IPv6
Answer: B — Historically discouraged; now subnet-zero is allowed. - Why do banks use subnetting?
A. To use single IP for entire bank
B. For security, management, and efficient IP usage
C. To encrypt data automatically
D. To avoid using routers
Answer: B — subnetting provides security, organization, and IP savings. - What is a wildcard mask?
A. Inverse of subnet mask used in ACLs (access-lists)
B. Another name for subnet mask
C. A mask for broadcast addresses
D. Only used in IPv6
Answer: A — wildcard mask = inverse of subnet mask (used in Cisco ACLs). - Which is NOT a reserved/private IP block?
A. 10.0.0.0/8
B. 172.16.0.0/12
C. 192.168.0.0/16
D. 198.51.100.0/24
Answer: D — 198.51.100.0/24 is TEST-NET-2 (public test range), not private. - When summarizing 192.168.0.0/24 and 192.168.1.0/24, supernet mask becomes:
A. /24
B. /23
C. /22
D. /25
Answer: B — combining two /24 → /23 (192.168.0.0/23). - What does subnetting reduce on a network?
A. Security
B. Broadcast domain size
C. Number of routers required
D. IP address consumption always
Answer: B — subnetting reduces broadcast domain size. - Which mechanism translates private IPs to public IPs?
A. VLSM
B. NAT
C. CIDR
D. Subnetting
Answer: B — NAT (Network Address Translation) maps private to public. - All-ones subnet historically meant:
A. Broadcast subnet only
B. It was discouraged (but allowed today)
C. Same as subnet-zero
D. No relation to subnets
Answer: B — all-ones subnets were historically discouraged; now allowed.
41–50: Advanced & exam-style applied questions
- You have 200 hosts required in a subnet. Which mask is minimal that supports this?
A. /24
B. /25
C. /26
D. /27
Answer: A — /24 gives 254 usable hosts which covers 200. - Company has network 192.168.0.0/24 and needs 4 equal subnets. What is the new mask?
A. /23
B. /25
C. /26
D. /27
Answer: C — 4 subnets ⇒ borrow 2 bits ⇒ /24 + 2 = /26. - Given network 10.0.0.0/16, you need subnets each with 500 hosts. What prefix length is appropriate?
A. /23 (510 hosts)
B. /24 (254 hosts)
C. /22 (1022 hosts)
D. /25 (126 hosts)
Answer: A — /23 ⇒ host bits 9 ⇒ 2^9 − 2 = 510 usable. - What is the wildcard mask for 255.255.255.0?
A. 0.0.0.255
B. 255.255.255.0
C. 0.0.0.0
D. 255.255.255.255
Answer: A — wildcard = inverse = 0.0.0.255. - If you supernet 10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/24, 10.0.3.0/24 you get:
A. 10.0.0.0/22
B. 10.0.0.0/21
C. 10.0.0.0/20
D. 10.0.0.0/23
Answer: A — combining four /24 → /22. - Which is the loopback address range for IPv4?
A. 127.0.0.0/8
B. 10.0.0.0/8
C. 192.168.0.0/16
D. 169.254.0.0/16
Answer: A — 127.0.0.0/8 reserved for loopback. - Automatic Private IP Addressing (APIPA) uses which range?
A. 10.0.0.0/8
B. 169.254.0.0/16
C. 192.168.0.0/16
D. 172.16.0.0/12
Answer: B — APIPA uses 169.254.0.0/16 when DHCP fails. - Which mask is used to create 8 subnets from a /24 network?
A. /27
B. /26
C. /25
D. /28
Answer: A — need 3 borrowed bits (2^3=8) → /24 + 3 = /27. - How many /28 subnets can be created from a /24 network?
A. 4
B. 8
C. 16
D. 32
Answer: C — /28 uses 4 host bits (16 subnets): (2^(28−24)=2^4=16). - Design question (choose best): You need subnets for departments requiring 100, 50, 12 hosts. Which approach is best?
A. Use fixed /24 for all
B. Use VLSM to allocate /25, /26, /28 respectively
C. Use /16 and assign hosts randomly
D. Use NAT only
Answer: B — VLSM lets you allocate appropriate masks (/25 →126 hosts, /26→62, /28→14).
🎯 Final Summary for Quick Revision
- Subnetting = dividing networks
- Helps in security, IP saving, management
- Subnet mask decides network/host bits
- CIDR notation = /24, /25, /28 etc
- Hosts formula = 2^(host bits) − 2
- Important masks:
- /24 → 254 hosts
- /25 → 126
- /26 → 62
- /27 → 30
- Banks use subnetting for branch LANs, ATMs, server networks, security zones.
⭐ SUPERnetting – Full Easy Explanation for Banking Exams
Supernetting is an important networking topic, often asked in competitive exams.
It is the opposite of subnetting, so understanding both is important for scoring well.
🌟 1. What is Supernetting?
✔ Supernetting means combining multiple smaller networks into one larger network.
✔ It is also called Route Aggregation, Route Summarization, or Prefix Aggregation.
✔ It reduces the number of routing table entries in routers.
✔ Commonly used by ISPs (Internet Service Providers) and large organizations.
🌟 2. Why do we need Supernetting?
Supernetting is needed for:
✔ 1. Reducing routing table size
Fewer entries → faster routing → better performance.
✔ 2. Simple and efficient routing
Instead of advertising many small routes, one big route is announced.
✔ 3. Saving bandwidth
Less routing information → less overhead.
✔ 4. Improves internet stability
Avoids router overloads.
🌟 3. Difference: Subnetting vs Supernetting
| Feature | Subnetting | Supernetting |
|---|---|---|
| Purpose | Divide a big network into small networks | Combine small networks into one big network |
| Mask | Mask becomes longer (e.g., /24 → /26) | Mask becomes shorter (e.g., /24 → /23) |
| Used By | LANs, banks, offices | ISPs, large networks |
| Hosts | Hosts per network ↓ | Hosts per network ↑ |
| Concept | Borrow bits from host | Give bits back to host |
Supernetting = opposite of Subnetting.
🌟 4. Important Term: CIDR (Classless Inter-Domain Routing)
Supernetting works only in CIDR format.
Example:
- 192.168.0.0/24
- 192.168.1.0/24
CIDR allows routers to combine these into 192.168.0.0/23.
🌟 5. How Supernetting Works (Very Simple Explanation)
To combine two or more networks:
✔ Step 1: All networks must be continuous
Example:
- 192.168.4.0
- 192.168.5.0
- 192.168.6.0
- 192.168.7.0
These are continuous networks.
✔ Step 2: Subnet masks must be same
Example: All must be /24.
✔ Step 3: Addresses must be aligned (on correct boundary)
For combining 4 networks:
Boundary size = 4 × block size
= 4 × 256
= 1024
(we use binary to verify alignment)
✔ Step 4: New prefix length becomes shorter
Example:
4 networks of /24 → supernet mask = /22
Why /22?
Because:
- /24 combined with 4 networks → reduce mask by 2 bits → /22
🌟 6. Supernetting Examples
⭐ Example 1: Combine two Class C networks
Given:
- 192.168.0.0/24
- 192.168.1.0/24
Combined result:
👉 192.168.0.0/23
Why /23?
- Combining 2 networks = 2 × 256 = 512 addresses
- /23 gives 512 addresses
- /23 is one bit shorter than /24
⭐ Example 2: Combine four networks
Given:
- 10.10.0.0/24
- 10.10.1.0/24
- 10.10.2.0/24
- 10.10.3.0/24
Combined result:
👉 10.10.0.0/22
Because:
- 4 networks require 2 bits (2² = 4)
- So prefix is shortened by 2 bits: /24 → /22
⭐ Example 3: Combine 8 networks
Given:
- 192.168.16.0/24 to 192.168.23.0/24 (eight networks)
Combined result:
👉 192.168.16.0/21
Because:
- 8 = 2³ → reduce mask by 3 bits
- /24 → /21
🌟 7. How to Know if Supernetting is Possible?
You must check 3 rules:
✔ Rule 1: Networks must be consecutive
Not allowed: 192.168.0.0, 192.168.2.0, 192.168.3.0 (gap exists)
✔ Rule 2: Networks must have same subnet mask
All must be /24 or /22 etc.
✔ Rule 3: First network address must be aligned
Example: For 4 networks (/24 each) the first must be
- 0
- 4
- 8
- 12
etc.
Binary alignment ensures proper summarization.
🌟 8. Advantages of Supernetting
- ✔ Reduces routing table size
- ✔ Reduces CPU load on routers
- ✔ Saves bandwidth
- ✔ Improves network performance
- ✔ Makes routing more efficient
- ✔ Helps in ISP-level route advertisement
- ✔ Improves scalability of large networks
🌟 9. Supernetting in Banking Sector (Exam-Oriented)
Banks do not usually perform supernetting inside branches.
But it is used by:
- Bank Data Centers
- WAN Network Teams
- ISP connections for bank WAN
- Core banking network aggregation
- MPLS / VPN routes
- Network security appliances
Supernetting helps banks aggregate multiple branch routes into a single route.
Example:
Instead of advertising 50 branch routes:
- 10.10.1.0/24
- 10.10.2.0/24
…
Router advertises: 10.10.0.0/20
🌟 10. CIDR Aggregation Table (Very Useful for Exams)
| Number of /24 Networks | Supernet Mask |
|---|---|
| 2 | /23 |
| 4 | /22 |
| 8 | /21 |
| 16 | /20 |
| 32 | /19 |
| 64 | /18 |
Use this table for quick exam answers.
🌟 11. Common MCQ Points (Most Asked in Exams)
- Supernetting = opposite of subnetting
- Mask gets shorter (e.g., /24 → /22)
- Used for route summarization
- Reduces routing table entries
- Works with CIDR, not classful addressing
- Networks must be continuous + same mask
- /23 combines two /24 networks
- /22 combines four /24 networks
- Used mainly by ISPs & large networks
🌟 12. Quick Summary (Easy to Memorize)
- Supernetting = merging networks
- Uses shorter prefix
- Reduces routing table size
- Supports efficient routing
- Needs continuous networks
- Needs same subnet mask
- Used by ISPs and large organizations
- Opposite of subnetting
- Very important for competitive exams
⭐ MCQs on Supernetting (Most Important)
(Answers with explanations included)
1. Supernetting is also known as:
A. Subnetting
B. Route Aggregation
C. IP Spoofing
D. NAT
Answer: B
Explanation: Supernetting = Route Aggregation / Route Summarization.
2. Supernetting does the opposite of:
A. NAT
B. VLAN
C. Subnetting
D. Routing
Answer: C
Explanation: Subnetting divides networks; supernetting combines them.
3. Supernetting uses a ___ subnet mask.
A. Longer
B. Shorter
C. Same
D. Dynamic
Answer: B
Explanation: Mask becomes shorter (e.g., /24 → /23 → /22).
4. Supernetting is mostly used by:
A. End users
B. LAN administrators
C. ISPs
D. Bluetooth networks
Answer: C
Explanation: Supernetting is common in ISP routing & large networks.
5. Combining two /24 networks results in:
A. /25
B. /26
C. /23
D. /28
Answer: C
Explanation: Two /24 → /23 (512 IPs).
6. What is the supernet of 192.168.0.0/24 and 192.168.1.0/24?
A. 192.168.0.0/25
B. 192.168.0.0/23
C. 192.168.0.0/22
D. 192.168.0.0/24
Answer: B
Explanation: 0.0 + 1.0 = 2 networks → reduce mask by 1 bit → /23.
7. Which of these is a requirement for supernetting?
A. Networks must be random
B. Different subnet masks
C. Networks must be continuous
D. IPs must be private only
Answer: C
Explanation: Supernetting requires consecutive networks.
8. What is the supernet of 10.10.0.0/24 – 10.10.3.0/24?
A. 10.10.0.0/24
B. 10.10.0.0/25
C. 10.10.0.0/22
D. 10.10.0.0/19
Answer: C
Explanation: Four /24 → /22.
9. Supernetting is performed in:
A. CIDR
B. Classful addressing
C. ARP
D. SMTP
Answer: A
Explanation: CIDR (Classless Inter-Domain Routing) supports supernetting.
10. Supernetting reduces:
A. Bandwidth
B. Broadcasts
C. Routing table entries
D. DHCP leases
Answer: C
Explanation: Goal = fewer routing entries.
11. What is the supernet mask for combining 8 class C networks?
A. /24
B. /21
C. /25
D. /20
Answer: B
Explanation: 8 networks → reduce mask by 3 bits → /21.
12. Supernetting helps in:
A. Increasing ARP requests
B. Summarizing routes
C. Increasing number of routers
D. Decreasing speed
Answer: B
Explanation: Supernetting = route summarization.
13. Requirement for supernetting:
A. IP addresses must begin on correct boundary
B. Broadcast addresses must match
C. Gateway must be same
D. Subnet ID must be 0
Answer: A
Explanation: Alignment boundary (e.g., multiples of 2 or 4) is required.
14. Combining 16 networks of /24 results in:
A. /20
B. /21
C. /23
D. /18
Answer: A
Explanation: 16 = 2⁴ → /24 − 4 = /20.
15. Which mask aggregates four Class C networks?
A. 255.255.252.0
B. 255.255.254.0
C. 255.255.240.0
D. 255.255.248.0
Answer: A
Explanation: 255.255.252.0 = /22 = 4 networks combined.
16. Supernetting decreases which type of overhead?
A. Transmission overhead
B. Routing overhead
C. DHCP overhead
D. DNS overhead
Answer: B
Explanation: Fewer routes → less overhead.
17. Combining 192.168.4.0/24 – 192.168.7.0/24 results in:
A. /23
B. /22
C. /21
D. /25
Answer: B
Explanation: 4 networks → /22.
18. Supernetting is used for:
A. Classful networks only
B. Reducing broadcast domains
C. Providing route summarization
D. Creating VLANs
Answer: C
19. The combined network of 172.16.0.0/16 and 172.17.0.0/16 is:
A. 172.16.0.0/15
B. 172.16.0.0/17
C. 172.16.0.0/18
D. Not possible
Answer: A
Explanation: Two /16 → /15.
20. A shorter prefix means:
A. More hosts
B. Fewer hosts
C. Same number of hosts
D. No hosts
Answer: A
Explanation: Shorter prefix → larger network.
21. Supernetting is commonly used for:
A. LAN segmentation
B. MPLS routing
C. Wi-Fi expansion
D. Antivirus updates
Answer: B
Explanation: MPLS & WAN routers use route summarization.
22. Supernetting helps in:
A. Reducing collisions
B. Reducing ARP replies
C. Reducing routing entries
D. Reducing MAC addresses
Answer: C
23. Combining 192.168.10.0/24 & 192.168.11.0/24 requires checking:
A. Both are even numbers
B. Both are continuous networks
C. Both are private networks
D. Both are same class
Answer: B
24. “Prefix aggregation” refers to:
A. DNS caching
B. Port forwarding
C. Supernetting
D. Subnetting
Answer: C
25. Boundary for combining 4 networks (/24 each) is:
A. Multiple of 2
B. Multiple of 4
C. Multiple of 8
D. Multiple of 16
Answer: B
Explanation: 4 networks = must start at 0, 4, 8, 12 etc.
26. Supernetting is NOT possible when:
A. Networks are consecutive
B. Subnet masks are equal
C. Networks are unrelated or non-adjacent
D. Using CIDR
Answer: C
27. Combining 2 networks reduces prefix by:
A. 1 bit
B. 2 bits
C. 3 bits
D. 4 bits
Answer: A
28. Supernet mask for 32 networks of /24 is:
A. /21
B. /20
C. /19
D. /18
Answer: C
Explanation: 32 = 2⁵ → /24 − 5 = /19.
29. Supernetting improves:
A. Throughput of switches
B. Routing efficiency
C. Email delivery
D. NAT performance
Answer: B
30. When 192.168.0.0/24 → 192.168.3.0/24 are combined → mask is:
A. /22
B. /21
C. /23
D. /25
Answer: A
Explanation: 4 networks → /22.