Top 50 Scenario-Based Questions on CCNA

  • By Gandhar Bodas
  • June 4, 2024
  • CCNA
Top 50 Scenario-Based Questions on CCNA

Top 50 Scenario-Based Questions on CCNA

Discover the Top 50 Scenario-Based Questions on CCNA. Prepare for your certification with practical challenges covering networking concepts and troubleshooting.

Q1) Which devices can be configured as a default gateway in a  LAN Network? 


In a home or small office environment, the default gateway is a device, such as a DSL router or cable router that connects the local network to the Internet. 


Q2) What is the function of ARP in LAN? 


ARP (Address Resolution Protocol) plays a crucial role in local area networks (LANs) by facilitating communication between devices on the same network. Its primary function is to map a known IP  address to a corresponding physical (MAC) address in a network. 


Here’s how ARP works: 

  1. IP to MAC Address Resolution: When a device in a LAN  wants to communicate with another device using its IP address,  it needs to know the corresponding MAC address. ARP is used  to resolve the IP address to the MAC address. 
  2. ARP Request: If a device (let’s call it Device A) wants to communicate with another device (Device B) on the same network but doesn’t know Device B’s MAC address, it sends out an ARP request broadcast packet to the entire local network.  This ARP request contains the IP address of Device B. 
  3. ARP Reply: The device with the matching IP address (Device  B) responds to the ARP request with its MAC address. This response is unicast, meaning it goes directly to the requesting device (Device A). 
  4. Address Resolution: Once Device A receives the ARP reply, it  now knows the MAC address corresponding to the IP address of  Device B. It can then use this information to frame Ethernet packets and communicate directly with Device B on the LAN.
  5. ARP Cache: To optimize future communications, devices maintain an ARP cache, which is a table that stores the mapping of IP addresses to MAC addresses. This helps in avoiding frequent ARP broadcasts for devices that have recently communicated. 

ARP is a fundamental protocol for communication within a LAN and is essential for the proper functioning of Ethernet-based networks. It operates at the data link layer (Layer 2) of the OSI model. 


Q3) A LAN Switch needs to be procured for terminating both IP  Phones and PCs on each of port. What are the basic considerations while selecting the Switch? 


When selecting a LAN switch to terminate both IP Phones and PCs on each port, there are several important considerations to ensure that the switch meets the requirements of your network. Here are some  basic considerations: 

  1. Port Density: 

Ensure the switch has enough ports to accommodate the total number of IP Phones and PCs you plan to connect.  Consider future growth to avoid outgrowing the switch too quickly. 

  1. Port Speed: 

Choose a switch with sufficient port speed. Gigabit  

Ethernet (1 Gbps) is common and suitable for most  

applications. If needed, consider switches with 10 Gigabit  Ethernet ports. 

  1. Power over Ethernet (PoE): 

If your IP Phones require power, select a switch with  Power over Ethernet (PoE) capability. PoE eliminates the need for separate power adapters for IP Phones,  

simplifying installation and maintenance.

  1. Quality of Service (QoS): 

QoS features are crucial for ensuring optimal voice and data traffic performance. Look for a switch that supports  QoS to prioritize voice traffic for IP Phones. 

  1. VLAN Support: 

Ensure that the switch supports VLANs if you plan to segregate voice and data traffic into different VLANs for security and performance reasons. 

  1. Managed vs. Unmanaged: 

Consider whether you need a managed or unmanaged switch. A managed switch provides more control over network configurations, VLANs, and monitoring. 

  1. Layer 2 vs. Layer 3: 

Determine if you need Layer 2 switching (basic switching)  or Layer 3 switching (routing capabilities). If you have multiple VLANs and need inter-VLAN routing, a Layer 3  switch may be necessary. 

  1. Stacking: 

Stacking allows you to combine multiple switches into a single logical unit, simplifying management and increasing capacity. Consider stacking options if scalability is  


  1. Redundancy and Reliability: 

Look for features like link aggregation (LACP) and  

redundant power supplies to enhance network reliability.  These features help prevent network downtime due to hardware failures. 

  1. Budget: 

Consider your budget constraints. While high-end switches with advanced features are beneficial, they may come at a higher cost. Balance your requirements with your budget.

  1. Vendor Support and Reputation: 

Choose a reputable vendor with good customer support.  This ensures that you can get assistance if issues arise and that firmware updates are available. 

  1. Security Features: 

Check for security features such as MAC address filtering,  port security, and support for network access control  (NAC) to enhance the overall security of your network. 


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Q4) A web server is installed inside the LAN environment to be accessed by local users. Generally which protocol and port number is used to access Web Server content? 


The protocol commonly used to access web server content is  HTTP (Hypertext Transfer Protocol).  

HTTP is the foundation of data communication on the World  Wide Web and is used for transferring hypertext (web pages)  between a web server and a web browser. 

The default port number for HTTP is 80.  

Therefore, when accessing web server content using HTTP,  local users typically connect to the server using a URL like  http://server_IP_address or http://hostname, where  server_IP_address is the IP address of the web server. 

It’s important to note that while HTTP is the standard protocol for unsecured communication, HTTPS (Hypertext Transfer  Protocol Secure) is commonly used for secure communication. 

HTTPS operates over a secure, encrypted connection, and its default port number is 443.  

To access a web server using HTTPS, the URL would be specified as https://server_IP_address or https://hostname. HTTP: Port 80 and HTTPS: Port 443

When users access a web server inside a LAN environment,  they typically use a web browser to connect to the server using either HTTP or HTTPS, depending on the desired level of security. 


Q5) What is the role of a proxy server? 


Def: A proxy server acts as an intermediary between clients, like web browsers or other applications, and the internet. It serves several  functions: 

  1. a) Performance Enhancement: Proxy servers can cache frequently accessed resources, such as web pages, images, or files. When a client requests a resource, the proxy server checks if it has a local copy and serves it directly to the client,  eliminating the need to retrieve it from the internet. This caching feature can significantly reduce bandwidth usage and improve response times for clients. 
  2. b) Anonymity and Privacy: Proxy servers can obscure the IP  addresses of clients by acting as a middleman between clients and the internet. This can offer users a level of anonymity since the target server only sees the IP address of the proxy server, not the client’s IP address. It also helps protect privacy by preventing websites from directly tracking users’ browsing habits. 
  3. c) Content Filtering and Access Control: Proxy servers enforce access policies by filtering requests based on criteria like URL,  content type, or source IP address. This allows organizations to block access to specific websites or types of content deemed 

inappropriate or unrelated to work. Conversely, it can also restrict access to internal resources from external networks. 

  1. d) Security: Acting as a barrier between clients and the internet,  proxy servers provide an additional layer of security. They inspect incoming and outgoing traffic for malicious content, 

such as malware or phishing attempts, and block or sanitize it before reaching the client. Proxy servers can also implement encryption and decryption for secure communication, enhancing data security. 

  1. e) Load Balancing: In large-scale deployments, multiple proxy servers can distribute incoming requests across multiple backend servers. This load balancing ensures optimal performance and availability for clients accessing web services. 


Q6) What is the significance of 

The IP address 127.0. 0.1 is called the loopback address and is used by a computer to refer to itself. It is also known as localhost.  When a server is running on your local PC, it will be accessible at  127.0 


Q7) What is the maximum data transmission speed of Category 5,  Category 5e, and Category 6 UTP cables? 


  1. a) Category 5 (Cat5): Cat5 cables can transmit data at speeds of up to 1000 Mbps (1 Gbps) over a maximum distance of 100  meters (328 feet). However, Cat5 is now less commonly used due to its limited bandwidth compared to newer cable categories. 
  2. b) Category 5e (Cat5e): Cat5e cables also support speeds of up to  1000 Mbps (1 Gbps) but provide improved performance and reduced crosstalk compared to Cat5. Cat5e is widely adopted in modern installations and is backward compatible with Cat5. 
  3. c) Category 6 (Cat6): Cat6 cables support higher data transmission speeds, up to 10 Gbps, over a maximum distance of 55 meters (180 feet) for 10GBASE-T applications. For  1000BASE-T (Gigabit Ethernet) applications, Cat6 cables can cover the same maximum distance as Cat5e, up to 100 meters  (328 feet).


Q8) What are the 3 types of transmission modes in between 2  devices?  


Transmission modes define the direction of data flow between two communicating devices. Here are three types: 

  1. a) Simplex: In simplex mode, data flows in only one direction between the sender and the receiver. The communication is unidirectional, meaning one device can only send data, and the other can only receive. An example of simplex mode is a keyboard or a mouse sending data to a computer. 
  2. b) Half-duplex: Half-duplex mode allows data transmission in both directions, but not simultaneously. Devices can both send and receive data, but not at the same time. They take turns sending and receiving. Walkie-talkies use half-duplex mode,  where one person talks while the other listens, and then they  switch roles. 
  3. c) Full-duplex: Full-duplex mode enables simultaneous two-way communication between devices. Both devices can send and receive data simultaneously, allowing for faster and more efficient communication. Examples of full-duplex communication includes telephone conversations and most modern computer networks.


Q9) What is the default encapsulation type of Ethernet interfaces on Cisco Routers? 


  • The default encapsulation type of Ethernet interfaces on Cisco routers is Ethernet II, also known as Ethernet Version 2  (Ethernet II or Ethernet 802.3). 
  • This encapsulation method is widely used and is the default setting for Ethernet interfaces on Cisco routers unless explicitly configured otherwise.  
  • It’s used to frame Ethernet packets and is compatible with most  Ethernet networks and devices. 


Q10) How can communication across various VLANs be controlled in a LAN environment? 


Inter-VLAN Routing: Inter-VLAN routing allows communication between different VLANs by routing traffic between them through a router or a layer 3 switch. This can be achieved by configuring router interfaces or SVIs (Switched Virtual Interfaces) for each VLAN. 

Access Control Lists (ACLs): ACLs can be implemented on routers or layer 3 switches to control the flow of traffic between VLANs based on criteria such as source/destination IP addresses, port numbers, or protocols. ACLs can permit or deny specific types of traffic between VLANs. 

VLAN Access Control Lists (VACLs): VACLs are used to filter traffic within a VLAN, including traffic destined for other VLANs.  They are applied to VLANs on a layer 3 switch and can filter traffic based on IP addresses, MAC addresses, or protocols. 

Private VLANs (PVLANs): PVLANs partition a single VLAN into multiple sub-VLANs, allowing finer control over communication between devices within the same VLAN. PVLANs can restrict communication between certain ports or groups of ports within the same VLAN while allowing communication with other VLANs. 

Firewalls: Firewalls can be deployed between VLANs to control and filter traffic based on security policies. They can inspect traffic at the network layer and apply rules to allow or deny traffic between  VLANs based on various criteria such as source/destination IP  addresses, port numbers, or application protocols.

Virtual Routing and Forwarding (VRF): VRF allows multiple routing instances to coexist within the same physical infrastructure,  enabling separate routing tables for each VLAN. This provides isolation and control over communication between VLANs by routing traffic through separate virtual routing instances. 


Q11) How can communication across various VLANs be controlled in a LAN environment? 


In a switch without VLANs, all connected devices are part of the same broadcast domain but separate collision domains. 

Broadcast Domain: A broadcast domain is a logical division of a network where all devices can receive each other’s broadcast messages. Since there are no VLANs, all devices connected to the switch are in the same broadcast domain. Therefore, there is only one broadcast domain in this scenario. 

Collision Domain: A collision domain is a network segment where collisions can occur. In a switch, each port is its own collision domain. With 4 computers connected to the switch, each computer is connected to a separate port. Therefore, there are 4 collision domains. 

So, in this scenario: 

  1. a) Number of broadcast domains: 1 
  2. b) Number of collision domains: 4 


Q12) When the administrator issues the command “arp –a” on one of the PC, the Physical address entry against is B: B: B:  B. What could be the cause of the Internet not working? 


It seems there might be an issue with ARP (Address Resolution  Protocol) cache poisoning or an incorrect ARP entry. When a device on a network needs to communicate with another device, it typically uses ARP to resolve the MAC address of the target IP address.

In this scenario, the administrator issues the “arp -a” command on a  PC and finds the physical address entry against to be  different from what’s expected (B:B:B 

instead of A:A:A) suggests a potential ARP spoofing or cache poisoning attack. 

Here’s what could be happening: 

  • ARP Cache Poisoning: An attacker could be sending false  ARP messages to the LAN, mapping the IP address of the  gateway ( to a different MAC address (B:B:B) that belongs to the attacker’s machine instead of the DSL router  (A:A:A). 
  • Misconfiguration: There might be a misconfiguration either on the router or on the switch, causing the ARP entries to become corrupted or incorrect. 
  • Malware: A malware-infected device on the network could be deliberately poisoning the ARP cache to intercept traffic or  disrupt connectivity. 

To resolve the issue: 

  • Flush ARP Cache: Flush the ARP cache on the affected devices to remove the incorrect entry. On Windows, this can be done with the command “arp -d”. 
  • Investigate Network Traffic: Use network monitoring tools to analyze traffic on the LAN for any signs of ARP spoofing or unusual activity. 
  • Security Measures: Implement measures to prevent ARP  spoofing attacks, such as ARP inspection or port security features on the switch. 
  • Update Security: Ensure all devices on the network have up-to-date security software to detect and prevent malware infections. Verify Configuration: Double-check the configuration of the  router and switch to ensure there are no misconfigurations  causing the ARP cache inconsistency.


Q13) How many hosts IPs can be given from subnet 


The subnet falls within the Class B private IP address range. With a subnet mask of /21, it means that 21 bits are reserved for the network portion of the address, leaving 11 bits for the host portion. 

The formula to calculate the number of host IPs in a subnet is 2n−22^n – 22n−2, where nnn is the number of host bits. 

In this case, n=11n = 11n=11,  

So: 211−2=2048−2=20462^{11} – 2 = 2048 – 2 =  


So, there can be 2046 usable host IP addresses in the subnet 


Q14) What is the maximum length of an Ethernet packet? 


  • The maximum length of an Ethernet packet, also known as the  Maximum Transmission Unit (MTU), depends on the Ethernet standard being used. 
  • For Ethernet II (Ethernet Version 2) commonly used in modern networks, the maximum length of an Ethernet packet is 1518  bytes, including 14 bytes for the Ethernet header, 4 bytes for the  Frame Check Sequence (FCS), and up to 1500 bytes of data. 
  • For IEEE 802.3 Ethernet, which includes variants like 10BASE T, 100BASE-TX, and 1000BASE-T, the maximum length of an  Ethernet packet is 1522 bytes, including 18 bytes for the  Ethernet header, 4 bytes for the Frame Check Sequence (FCS),  and up to 1500 bytes of data.


Q15) What is the difference between DOT1q and ISL encapsulation?


The IEEE 802.1Q (Dot1Q) and Inter-Switch Link (ISL) are two different methods used for VLAN (Virtual Local Area Network)  tagging and encapsulation in Ethernet networks. Here’s a breakdown  of the key differences between them: 


  • IEEE 802.1Q (Dot1Q): This is an open industry standard developed by the Institute of Electrical and Electronics  Engineers (IEEE). 
  • ISL: This was a proprietary VLAN encapsulation protocol developed by Cisco Systems. 

Tagging Method: 

  • Dot1Q: Dot1Q encapsulates Ethernet frames by adding a 4-byte  VLAN tag to the Ethernet frame header. This tag contains  VLAN information such as VLAN ID (VID), priority information, and type. 
  • ISL: ISL encapsulates entire Ethernet frames within a new frame, adding a 26-byte header and a 4-byte trailer. This means that ISL encapsulates the entire original Ethernet frame,  including the original Ethernet header, payload, and FCS (Frame  Check Sequence), and adds its own header and trailer. 


  • Dot1Q: Because it’s an open standard, Dot1Q is widely supported by various networking devices from different vendors. 
  • ISL: ISL is a Cisco proprietary protocol, so it’s mainly supported on Cisco devices. Non-Cisco devices may not support  ISL encapsulation.


  • Dot1Q: Dot1Q adds a 4-byte VLAN tag to the original Ethernet frame, resulting in minimal overhead. 
  • ISL: ISL adds a significant amount of overhead by encapsulating the entire Ethernet frame within another frame.  This additional overhead can reduce the available bandwidth on the network. 


  • Dot1Q: Dot1Q VLAN tags are readable by any device on the network, making it easier to implement VLANs across heterogeneous network environments. 
  • ISL: ISL encapsulation can provide a level of security by encapsulating the original Ethernet frame, making it less susceptible to sniffing or tampering by devices outside the  VLAN. However, since ISL is proprietary, it limits interoperability and flexibility in network design.


Q16) How many wires does the UTP cable have? 


  • Unshielded Twisted Pair (UTP) cable typically contains four pairs of twisted wires, totaling eight individual wires.  Each pair consists of two insulated copper wires twisted around each other.  
  • These pairs are color-coded for identification purposes, usually with colors such as blue, orange, green, and brown.  
  • UTP cables are commonly used in Ethernet networks for data transmission.


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Q17) In a Campus LAN setup where multiple buildings are being connected, a Ring topology is used across Switches (in Layer 2) in buildings. How many maximum switches (Buildings) can be connected in a ring and why? 


  • In a Campus LAN setup where multiple buildings are being connected using a Ring topology across switches in Layer 2, the maximum number of switches that can be connected depends on several factors including the network equipment, the type of switches, and the specific network requirements. 
  • One of the main reasons for this limitation is the propagation delay inherent in a ring topology.  
  • As data travels around the ring, each switch introduces a certain amount of delay, and this delay accumulates as the data packet circulates the ring.  
  • This can result in increased latency, which can negatively  impact network performance, especially in real-time  


  • Additionally, the more switches there are in the ring, the greater the likelihood of network failures or disruptions.  
  • If a single switch fails or experiences a problem, it can disrupt communication for all the switches downstream from it in the ring.  
  • As the number of switches increases, so does the complexity of troubleshooting and maintaining the network. 
  • Therefore, while there is no fixed maximum number of switches that can be connected in a ring, it’s generally recommended to limit the size of the ring to a manageable number of switches to ensure optimal network performance and reliability.  
  • Depending on the specific requirements and constraints of the campus LAN setup, alternative topologies such as a hierarchical or mesh topology may be more suitable for larger networks.


Q18) In a network with 10 switches, how many root switches will  be there? 


  • In a network with 10 switches, there will typically be only one root switch.  
  • The root switch is the bridge with the lowest Bridge ID (BID)  value, which is usually determined by the switch with the lowest  MAC address.  
  • All other switches in the network will have paths leading back to this root switch, forming a tree-like structure. 


Q19) Some new VLANs need to be configured in a switched network of multiple switches. This will consume a lot of manhours and management has called for a solution to reduce time in creation and propagation of VLAN information across all switches. What would be the solution? 

What are the prerequisites to form an EtherChannel? ➔ 

To reduce the time and effort required for configuring and propagating VLAN information across multiple switches,  implementing VLAN Trunking Protocol (VTP) can be a beneficial solution. 

VTP enables the automatic propagation of VLAN configuration information between switches in a network.  

When a new VLAN is created on one switch, VTP ensures that this  VLAN information is distributed to all other switches within the same  VTP domain.  

This significantly reduces the manual effort and time required to configure VLANs across multiple switches.

To implement VTP effectively, consider the following  prerequisites and recommendations: 

1) VTP Domain: All switches participating in VTP must be configured with the same VTP domain name. This ensures that they can communicate and synchronize VLAN information. 

2) VTP Modes: Switches can operate in one of three VTP modes:  Server, Client, or Transparent. 

  • Server mode: Allows the switch to create, modify, and  delete VLANs and share this information with other  

switches in the same VTP domain. 

  • Client mode: Receives and synchronizes VLAN  

information from VTP servers but cannot create or modify  VLANs. 

  • Transparent mode: Forwards VTP advertisements but does not participate in VLAN information synchronization. It’s useful when connecting switches with different VTP  domains or when you want to locally configure VLANs without affecting the VTP domain. 

3) VTP Version: Ensure that all switches are configured to use the same version of VTP. Cisco switches typically support versions  1, 2, and 3. Choose the appropriate version based on  

compatibility and feature requirements. 

4) VTP Password: Setting a VTP password adds a layer of security to the VTP domain, preventing unauthorized switches from joining and affecting VLAN configurations. 

5) Trunk Configuration: VLAN information is exchanged between switches over trunk links. Ensure that trunk links are properly configured and operational between all switches participating in VTP.


Q20) What is the smallest IPv4 subnet mask that can be applied to a network containing up to 30 devices? 


1) To determine the smallest IPv4 subnet mask that can accommodate up to 30 devices, you need to find the smallest subnet size that can provide at least 30 host addresses. 

2) IPv4 subnet masks are typically represented in CIDR (Classless  Inter-Domain Routing) notation, which uses a slash followed by the number of significant bits in the subnet mask. For example,  a /24 subnet mask means the first 24 bits are the network portion, and the remaining 8 bits are available for hosts. 

3) To accommodate at least 30 devices, you need a subnet that  provides at least 30 usable host addresses. In binary, the number of host addresses needed is greater than or equal to 30 but less  than the next power of 2 (which is 32 in this case). 

4) The formula to calculate the number of hosts in a subnet with n  significant bits is 2^(32-n) – 2 (subtracting 2 for the network and broadcast addresses). 

Let’s find the smallest subnet mask: 

  • Start with 2^(32-n) = 30+2 = 32 
  • Solve for n: 2^(32-n) = 32 
  • Take the log base 2 of both sides: 32-n = log2(32) = 5 Solve for n: n = 32 – 5 = 27 

So, the smallest subnet mask that can accommodate at least 30  devices is a /27 subnet mask, which provides 30 usable host addresses.



Q21) An access point without any external power source is connected to a LAN switch but does not power up. What could be the probable cause? 


There could be several potential reasons why the access point isn’t  powering up despite being connected to a LAN switch without an  external power source: 

1) PoE (Power over Ethernet) Issue: If the access point relies on  PoE to receive power from the LAN switch, there might be an issue with either the PoE injector or the switch itself. Ensure that  the switch supports PoE and is configured to provide power on the correct ports. 

2) Faulty Cable: The Ethernet cable connecting the access point to the LAN switch might be faulty or damaged. Try using a different cable to rule out this possibility. 

3) Incorrect Port Configuration: Make sure the access point is connected to a port on the LAN switch that is configured to provide power over Ethernet. Some switches require specific configurations to enable PoE on certain ports. 

4) Hardware Failure: The access point itself might be defective or experiencing hardware failure. Try connecting a different device to the same port on the switch to see if it powers up, or  try connecting the access point to a different PoE-enabled switch to determine if the issue lies with the access point. 

5) Power Budget Exceeded: If the LAN switch has a limited power budget for PoE devices, it’s possible that the total power  required by all connected devices exceeds the switch’s capacity.  Check the specifications of the switch to ensure it can provide enough power for the access point. 

6) Software Configuration Issue: In some cases, the access point may require specific software configurations to power up properly when connected to a LAN switch. Review the documentation for the access point to ensure it is configured correctly.


Q22) A new Trunk Link Is Configured On a catalyst Switch. Do we need to allow VLANs over the trunk link? 


1) Yes, when configuring a trunk link on a Catalyst switch, you typically need to allow specific VLANs to pass over the trunk link.  

2) By default, a trunk link carries traffic for all VLANs that exist on the switch.  

3) However, for security and efficiency reasons, it’s common practice to manually specify which VLANs are allowed to traverse the trunk link. 

4) This is achieved using the “switchport trunk allowed vlan”  command in Cisco IOS.  

5) By default, all VLANs are allowed to traverse the trunk, but you can restrict this by specifying only the VLANs you want to allow.  

6) This helps in controlling which VLANs can communicate over the trunk link, reducing unnecessary broadcast traffic and improving network security. 

Here’s an example of how you would configure a trunk link on a  Catalyst switch and allow specific VLANs: 

interface GigabitEthernet0/1 (or whichever interface you are  configuring) 

switchport mode trunk 

switchport trunk allowed vlan 10 


Q23) Which VTP mode allows the change of VLAN information on the switch? 


In VTP, switches can operate in one of three modes: 

1) Server Mode: In this mode, switches can create, modify, and delete VLANs, and these changes are propagated to other switches in the same VTP domain.

2) Client Mode: Switches in this mode cannot create, modify, or delete VLANs. They receive VLAN information from VTP  server switches and synchronize their VLAN databases accordingly. 

3) Transparent Mode: Switches in this mode don’t participate in  VTP domain-wide VLAN management. They simply pass VTP  messages through without processing them. They can create,  modify, and delete VLANs locally, but these changes are not advertised to other switches via VTP. 


Q24) What is meant by VLSM? 


1) VLSM stands for Variable Length Subnet Masking. It’s a technique used in network design to allocate IP addresses efficiently by allowing different subnets to have subnet masks of varying lengths, rather than all subnets within a network having the same subnet mask. 

2) With VLSM, larger subnets can be divided into smaller subnets,  each with its own unique subnet mask, based on the specific number of hosts required in each subnet. This allows for more efficient utilization of IP address space, as it reduces IP address wastage by allocating smaller subnets where needed and larger subnets where more hosts are anticipated. 

3) VLSM is especially useful in hierarchical network designs, such as in large enterprise networks, where different departments or  sections may require different numbers of hosts. It enables the  

network administrator to tailor the subnet sizes to the requirements of each subnet, optimizing address space usage and conserving IP addresses.

Q25) What is FTP and what is it used for? 



1) FTP, or File Transfer Protocol, is a standard network protocol used for transferring files between a client and a server on a computer network. 

2) It operates on the application layer of the TCP/IP protocol suite and is commonly used for uploading and downloading files  from a remote server over a TCP-based network, such as the  Internet. 

FTP is widely used for various purposes, including: 

  • Website Management: FTP is commonly used by web developers and administrators to upload files (such as HTML,  CSS, JavaScript, and media files) from their local machines to a web server. This allows them to update and maintain websites remotely. 
  • File Sharing: FTP facilitates the sharing of files between users on a network. Users can upload files to an FTP server for others to download, or they can download files from the server shared  by others. 
  • Software Distribution: Many software developers use FTP to distribute software updates, patches, and other files to users.  Users can download these files from FTP servers maintained by software companies. 
  • Backup and Archiving: FTP can be used for backing up files to a remote server, providing a secure offsite storage solution.  Organizations often use FTP for automated backups of critical data. 
  • Large File Transfers: FTP is suitable for transferring large files or batches of files that may be too large to send via email.  It offers a reliable method for transferring files over a network,  even over long distances. 
  • Anonymous FTP: Some FTP servers allow anonymous access,  where users can connect to the server without providing a username and password. This is often used for distributing publicly available files, such as software updates or public domain content.


Q26) While configuring NAT on the Router, which command would you place on the interface connected to the Internet? 

  1. a) ip nat inside 
  2. b) ip nat outside 
  3. c) ip outside global 
  4. d) ip inside local 


When configuring NAT (Network Address Translation) on a router,  the command you would typically use on the interface connected to  the internet is: 

Command: ip nat outside 


Q27) Which command will show us all the translations active on your router? 


To view all active NAT translations on a router, you can use the  following command: 

Command: show ip nat translations 

This command will display a list of all active NAT translations,  including the inside local address, inside global address, outside local address, and outside global address for each translation. 


Q28) Which command would we place on the interface on a private/inside/LAN network? 


To configure an interface on a private/inside/LAN network, you  typically use the following commands:

1) Assign an IP address and subnet mask to the interface: Command: ip address <IP_address> <subnet_mask> 

2) Enable the interface: 

Command: no shutdown 

3) Optionally, configure a description for the interface: Command: description <description> 

For example: Let’s say we want to configure the interface GigabitEthernet0/1 with an IP address of and a subnet  mask of for a LAN network: 

Router(config)# interface GigabitEthernet0/1 

Router(config-if)# ip address Router(config-if)# no shutdown 

Router(config-if)# description LAN Interface 


Router(config)#: This prompt indicates global configuration mode. 

Router(config-if)#: This prompt indicates the interface configuration mode for GigabitEthernet0/1. 

ip address Assigns the IP address and subnet mask to the interface. 

no shutdown: Enables the interface. 

description LAN Interface: Optional command to add a description to the interface.


Q29) When creating a pool of global addresses, which keyword can be used instead of the netmask command? 


1) Instead of using the term “netmask,” you can utilize the  “prefix-length” command when configuring a pool of global addresses. 

2) This command specifies the length of the prefix for the addresses in the pool, indicating the number of bits that are used for the network portion of the address.  

3) This approach ensures clarity and originality in your networking configurations. 


Q30) What is the maximum number of configurable NAT IP  pools? 


  • The maximum number of configurable NAT IP pools varies depending on the specific networking hardware and software being used.  
  • In general, the maximum number of configurable NAT IP pools can range from a few to hundreds or even thousands, depending on the capabilities of the device and the requirements of the  network.  
  • It’s essential to consult the documentation or specifications of the networking equipment or software being used to determine the exact limits in any given scenario. 


Q31) Which command will show you the summary of the NAT  configuration? 


Network Address Translation (NAT) provides several benefits in  networking: 

1) IP Address Conservation: NAT allows multiple devices within a private network to share a single public IP address. This 

conserves the limited pool of available public IP addresses,  which is particularly important as IPv4 addresses become increasingly scarce. 

2) Enhanced Security: NAT acts as a barrier between the internal network and the external internet by hiding the actual IP  addresses of devices within the network. This provides a level of security by obfuscating the internal network structure, making it harder for external entities to directly access devices within the  network. 


Q32) Explain the term – 

  • Inside Local 
  • Inside Global 
  • Outside Local 
  • Outside Global 


1) Inside Local: Inside Local refers to the local IP addresses of devices within a private network. These addresses are typically assigned by the network administrator and are used for communication within the internal network. Inside Local addresses are not routable on the public internet. 

2) Inside Global: Inside Global addresses are the public IP  addresses assigned to devices within the private network when they communicate with the outside world, such as accessing websites or sending emails. These addresses are used as the source address in outgoing packets from the internal network and are globally routable on the internet. 

3) Outside Local: Outside Local refers to the local IP addresses of devices outside the private network, typically on the internet.  These addresses are seen from the perspective of the internal network and are used for communication with external devices.

4) Outside Global: Outside Global addresses are the public IP  addresses of devices outside the private network, such as servers or routers on the internet. These addresses are globally routable and are used as the destination address for incoming packets from the internet to devices within the internal network. 


Q33) Which NAT command would you place on the interface on a  private (Inside LAN) network? 


On the interface facing the private (inside LAN) network, you would  typically configure NAT using the following command: 

Command = ip nat inside 

This command tells the router or firewall that traffic coming from the inside network should undergo NAT translation when going out to the internet-facing interface. It marks the interface as the “inside”  interface where private IP addresses reside, and NAT translation should occur for outbound traffic from this interface. 


Q34) What is the Difference between RIP v1 and RIP v2? ➔ 

RIP (Routing Information Protocol) versions 1 and 2 are both distance  vector routing protocols used in computer networks, but they differ in  several key aspects: 

1) Classless vs. Classful: RIP v1 is a classful routing protocol,  which means it doesn’t support the use of subnet masks in routing updates. This limitation makes it less flexible in handling modern, variable-length subnet masking (VLSM) and classless inter-domain routing (CIDR). On the other hand, RIP  v2 is a classless protocol, allowing for the transmission of subnet mask information along with routing updates, making it more efficient and flexible.

2) Authentication: RIP v2 supports authentication, which adds a layer of security to the routing updates exchanged between routers. This feature helps prevent unauthorized devices from injecting false routing information into the network. RIP  v1 lacks authentication support, making it more vulnerable to  various types of attacks such as spoofing and injection of false routing information. 

3) Multicast vs. Broadcast: RIP v2 uses multicast addresses  ( for RIP version 2) to send routing updates, which is more efficient in terms of bandwidth usage and scalability compared to the broadcast method used by RIP v1. Broadcasting routing updates can cause unnecessary traffic on the network,  especially in large networks. 

4) Route Tagging: RIP v2 introduces the concept of route tagging,  which allows routers to include additional information about routes in their updates. This information can be useful for implementing policies, filtering routes, and prioritizing certain routes over others. RIP v1 does not support route tagging. 

5) Support for IPv6: While both RIP v1 and v2 are primarily  designed for IPv4 networks, RIP v2 has the capability to support  IPv6 through extensions, making it more adaptable to evolving network technologies. RIP v1 lacks support for IPv6. 


Q35) What is the multicast address that RIP v2 uses?

The multicast addresses that RIP v2 uses is 


Q36) What does RIP v2 use to prevent routing loops? 

RIP v2 uses several mechanisms to prevent routing loops: 

Maximum Hop Count: RIP v2 sets a maximum hop count limit of  15 for a route. If a route’s hop count exceeds this limit, the route is considered unreachable and is not included in routing updates. This prevents packets from being endlessly forwarded in loops.

Split Horizon: Split Horizon is a technique used in distance vector routing protocols like RIP v2 to prevent routing information from being sent back in the direction it came from. This prevents loops by ensuring that a router does not advertise a route back to the router from which it learned about that route. 

Route Poisoning: In RIP v2, when a route becomes unreachable, the router advertises it with an infinite metric (hop count of 16), signaling to other routers that the route is no longer valid. This helps prevent loops by immediately informing other routers to avoid using that route. 

Hold-down Timer: RIP v2 employs a hold-down timer mechanism to prevent the routing table from being updated with potentially incorrect routing information. When a route goes down, the router sets a hold-down timer, during which it ignores any updates about that route. This prevents rapid, potentially unstable changes in the routing table. 


Q37) Is a subnet mask field available in an RIP v2 packet? ➔ 

  • Yes, a subnet mask field is indeed available in a RIP v2  (Routing Information Protocol version 2) packet.  
  • This field allows the router to convey subnet mask information along with the routing updates, enabling more precise routing decisions. 
  • RIP v2 is an enhancement over RIP v1 and includes additional features like support for Variable Length Subnet Masking  (VLSM) and CIDR (Classless Inter-Domain Routing), which require the inclusion of subnet mask information in the packet.  
  • This enhancement improves the efficiency and flexibility of routing in RIP networks.


Q38) What is the major benefit of dynamic routing protocol like  RIP over Static route? 


  • One significant benefit of dynamic routing protocols like RIP  (Routing Information Protocol) over static routes is their ability to adapt to network changes automatically.  
  • With RIP, routers can exchange routing information  dynamically, allowing them to update their routing tables in real time based on changes in network topology or link status.  
  • This dynamic nature enables RIP to respond quickly to network failures, congestion, or the addition/removal of network devices,  ensuring efficient and reliable packet forwarding.  
  • In contrast, static routes require manual configuration and do not adjust automatically to network changes, making them less flexible and more prone to errors, especially in large or dynamic networks. 

Q39) What route entry will be assigned to a dead or invalid route in case of RIP? 


  • In the Routing Information Protocol (RIP), when a route  becomes invalid or unreachable (often due to a link failure or  network topology change), the route entry is marked as  “unusable” or “invalid.”  
  • Instead of immediately removing the route from the routing table, RIP routers retain the route entry and mark it with a metric value of 16. 
  • This metric value indicates that the route is considered unreachable. 
  • However, routers continue to advertise these unreachable routes to neighboring routers, allowing them to inform the rest of the network about the change in topology.  
  • This process helps in convergence, where routers collectively update their routing tables to reflect the new network state. 
  • Eventually, after a certain period (usually around 180 seconds),  if the router still hasn’t received any updates confirming the route’s validity, it will remove the entry from its routing table altogether. 
  • This mechanism ensures that network routers are aware of changes in network topology and can adapt their routing tables accordingly, maintaining efficient packet forwarding even in the presence of network failures. 


Q40) Which command displays RIP routing updates ?


To display Routing Information Protocol (RIP) routing updates on a  Cisco router, you can use the following command: 

Command: show ip rip database 

This command provides information about the RIP routing table,  including routes learned from RIP updates, their metric values, and the next-hop routers.  

It allows network administrators to inspect the RIP routing database and verify the routes being advertised and learned through RIP  updates. 


Q41) What command is used to stop RIP routing updates from exiting out an interface but still allow the interface to receive RIP  route updates? 


In Cisco routers, you can use the “passive-interface” command in RIP  configuration mode to stop sending RIP updates out of an interface while still allowing the router to receive RIP updates on that interface.  Syntax: 

Router(config)# router rip 

Router(config-router)# passive-interface <interface>

Replace <interface> with the interface name where you want to stop sending RIP updates. This command will suppress outgoing RIP  updates on that interface while still allowing the router to receive updates. 


Q42) Which metric does RIP use? 


  • The Routing Information Protocol (RIP) uses several metrics to determine the best path to a destination network.  
  • The primary metric used in RIP is hop count, which represents the number of routers a packet must traverse to reach the destination network.  
  • RIP selects the route with the fewest hops as the best path. 

Q43) How does RIP v1 send Routing updates? 


  • RIP version 1 (RIPv1) sends routing updates as broadcast messages, using User Datagram Protocol (UDP) on port 520.  It broadcasts the entire routing table every 30 seconds to all routers in the network.  
  • Each router receiving the update then updates its own routing table accordingly.  
  • RIP v1 does not support authentication or subnet information in its updates. 


Q44) How does the switch perform the forwarding function? ➔ 

  • Switches perform the forwarding function by using a forwarding table, also known as a MAC address table.  
  • When a switch receives a frame, it examines the destination  MAC address of the frame. 
  • It then checks its forwarding table to determine which port the destination MAC address is associated with.  
  • If the MAC address is found in the table, the switch forwards the frame only to the port associated with that MAC address.  If the MAC address is not in the table, the switch floods the frame out of all ports except the one it was received on.  As frames are forwarded, the switch learns and updates its forwarding table with the source MAC address and the corresponding port.  
  • This process allows switches to efficiently forward frames to their intended destinations within a local area network. 


Q46) Which command will show directly connected neighbors? ➔ 

  • To view directly connected neighbors in a network, you can typically use the arp command on Unix-based systems or the arp  -a command on Windows.  
  • This command displays the ARP (Address Resolution Protocol)  cache, which contains information about IP addresses and their corresponding MAC (Media Access Control) addresses of devices on the local network.  
  • This information can help identify directly connected neighbors. 

Q47) A layer 2 switch has 5 PC’s connected to it’s ports. After restarting the switch, what would happen to the Mac address table of the switch? 


  • After restarting a Layer 2 switch, the MAC address table, also known as the MAC address forwarding table or CAM (Content  Addressable Memory) table, is typically cleared.  
  • This is because the switch loses all its learned MAC addresses in its memory. 
  • When the switch is restarted, it has to re-learn the MAC  addresses of the devices connected to its ports. 
  • As network traffic flows through the switch after the restart, it starts populating the MAC address table again by learning the source MAC addresses of incoming frames on its ports.  
  • This process is achieved through MAC address learning, where the switch records the source MAC address of each frame it  receives, associating it with the port from which it received the frame.  
  • Over time, the MAC address table repopulates with the MAC  addresses of the connected devices as they communicate with each other and with devices outside the local network. 


Q48) Your internet work consists entirely of Cisco devices. You have given a command “show cdp neighbours”. In the response,  you get “S” under the head “Capability”. What does the letter  “S” mean? 


The “S” under the “Capability” column in the output of the “show cdp  neighbours” command stands for “Switch.” This indicates that the neighboring device has been identified as a switch. CDP (Cisco  Discovery Protocol) is a Cisco proprietary protocol used to discover information about directly connected Cisco devices. 


Q49) Which LAN switch type waits for the collision window to pass before looking up the destination hardware address in the  MAC filter table and forwarding the frame? 


  • The LAN switch type that waits for the collision window to pass before looking up the destination hardware address in the MAC  filter table and forwarding the frame is known as a “store-and-forward” switch.  
  • In store-and-forward switching, the switch receives the entire frame before forwarding it. 
  • This allows the switch to check the frame for errors and collisions before forwarding it to the appropriate destination. 


Q50) If a switch receives a frame and the source MAC address is  not in the MAC address table but the destination address is, what will the switch do with the frame? 


  • If a switch receives a frame where the source MAC address is not in its MAC address table but the destination address is, the  switch will update its MAC address table with the source MAC  address and forward the frame out of the port associated with  the destination MAC address.  
  • This behaviour ensures that future frames destined for the  source MAC address can be correctly forwarded without  flooding the network unnecessarily. 


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