70+ Network Engineer L1 Interview Questions and Answers

Switches and routers are networking devices that help in data transmission. VLAN is a logical grouping of devices. OSI model and TCP/IP are networking protocols.

• Switches are used to connect devices within a network and forward data packets between them.

• Routers are used to connect different networks and forward data packets between them.

• VLAN is a logical grouping of devices that allows for better network management and security.

• OSI model is a conceptual model that describes ho...read more

DHCP is a network protocol that allows devices to obtain IP addresses and other network configuration settings automatically.

• DHCP stands for Dynamic Host Configuration Protocol.

• It is used to assign IP addresses dynamically to devices on a network.

• The DORA process in DHCP stands for Discover, Offer, Request, and Acknowledge.

• During the DORA process, a client sends a DHCP Discover message to find available DHCP servers.

• The DHCP server responds with a DHCP Offer message, providin...read more

To check uptime of Routers & Switches, use the show version command.

• Log in to the device using SSH or Telnet.

• Enter the show version command.

• Look for the line that starts with 'uptime'.

• The uptime will be displayed in the format of days, hours, minutes, and seconds.

• Alternatively, you can use network monitoring tools like Nagios, PRTG, or SolarWinds to monitor uptime.

• These tools can provide alerts when a device goes down or when uptime falls below a certain threshold.

Network protocols and port numbers are essential for communication between devices on a network.

• TCP/IP is the most commonly used protocol suite

• HTTP uses port 80, HTTPS uses port 443

• SMTP uses port 25, POP3 uses port 110, IMAP uses port 143

• FTP uses port 21, SFTP uses port 22

• DNS uses port 53

• SSH uses port 22

• Telnet uses port 23

Network classes are a way of dividing IP addresses into different ranges based on their first octet.

• There are five network classes: A, B, C, D, and E.

• Class A addresses range from 1.0.0.0 to 126.0.0.0.

• Class B addresses range from 128.0.0.0 to 191.255.0.0.

• Class C addresses range from 192.0.0.0 to 223.255.255.0.

• Class D addresses are used for multicast and range from 224.0.0.0 to 239.255.255.255.

• Class E addresses are reserved for future use and range from 240.0.0.0 to 255.255.255...read more

VLAN stands for Virtual Local Area Network. It is a logical grouping of devices on a network, allowing for better network management and security.

• VLANs divide a single physical network into multiple virtual networks.

• They help in reducing network congestion and improving network performance.

• VLANs can be configured on switches using commands like 'vlan database', 'vlan ', and 'interface switchport access vlan '.

OSI layers are a conceptual model for communication systems. There are 7 layers, each with a specific function.

• Layer 1 - Physical layer: deals with the physical aspects of data transmission

• Layer 2 - Data link layer: responsible for error-free transfer of data between nodes

• Layer 3 - Network layer: handles routing and forwarding of data packets

• Layer 4 - Transport layer: ensures reliable data transfer between end systems

• Layer 5 - Session layer: establishes, manages and terminate...read more

LAN/WAN refers to local area network and wide area network respectively. VLAN is a virtual LAN that allows for logical segmentation of a network.

• LAN is a network that covers a small geographical area, typically within a single building or campus.

• WAN is a network that spans a large geographical area, connecting multiple LANs or remote locations.

• VLAN is a virtual LAN that enables the creation of multiple logical networks within a single physical network infrastructure.

• VLANs pro...read more

DWDM stands for Dense Wavelength Division Multiplexing, OSPF is Open Shortest Path First, EIGRP is Enhanced Interior Gateway Routing Protocol, OLT is Optical Line Terminal, and ONU is Optical Network Unit.

• DWDM is a technology that multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths of laser light.

• OSPF is a routing protocol used for exchanging routing information between routers in an IP network.

• EIGRP is a Cisco proprietary rou...read more

Routing configuration is the process of setting up and managing the paths that network traffic takes between devices.

• Routing configuration involves configuring routing protocols, such as OSPF or BGP, on network devices.

• It also involves setting up static routes and defining network topologies.

• Routing configuration is important for ensuring efficient and reliable network communication.

• Examples of routing configuration tools include Cisco's IOS and Juniper's Junos OS.

TCP/IP, DNS, and DHCP are fundamental protocols used in computer networking.

• TCP/IP is a suite of communication protocols used to connect devices on the internet.

• DNS translates domain names into IP addresses.

• DHCP assigns IP addresses to devices on a network.

• TCP/IP is used for communication between devices, while DNS and DHCP are used for addressing and management.

• Examples of TCP/IP applications include web browsing, email, and file sharing.

OSPF, RIP, IGRP, and EIGRP are routing protocols used in networking to determine the best path for data packets to travel.

• OSPF (Open Shortest Path First) is a link-state routing protocol that uses Dijkstra's algorithm to calculate the shortest path.

• RIP (Routing Information Protocol) is a distance-vector routing protocol that uses hop count as a metric to determine the best path.

• IGRP (Interior Gateway Routing Protocol) is a distance-vector routing protocol developed by Cisco.

• E...read more

Root bridge election in a network is determined by the bridge ID and the lowest path cost to the root bridge.

• Root bridge is the bridge with the lowest bridge ID in the network.

• Bridge ID consists of a priority value and a MAC address.

• If two bridges have the same priority, the bridge with the lowest MAC address will become the root bridge.

• Each bridge calculates the path cost to the root bridge based on the cumulative cost of all links between them.

• The bridge with the lowest pat...read more

To configure 802.1x protocol, you need to set up authentication servers, configure network devices, and define access policies.

• Set up authentication servers such as RADIUS or TACACS+

• Configure network devices (switches, routers, wireless access points) to support 802.1x

• Define access policies for different user roles and devices

• Enable 802.1x on network ports and specify authentication methods (EAP-TLS, PEAP, etc.)

I will troubleshoot network issues by following a systematic approach to identify and resolve the root cause.

• Start by gathering information about the issue reported

• Check physical connections and cables

• Verify network configurations and settings

• Use network monitoring tools to identify any anomalies

• Isolate the issue by testing connectivity between devices

• Check for any network congestion or bandwidth issues

• Consult network documentation and seek help from colleagues if needed

Subnetting is the process of dividing a network into smaller subnetworks to improve performance and security.

• Subnetting helps in optimizing network performance by reducing network congestion.

• It allows for better organization and management of IP addresses.

• Subnetting enhances network security by isolating different parts of the network.

• Example: Dividing a large network into smaller subnets based on departments or locations.

Routing and switching are fundamental concepts in computer networking that involve directing and forwarding data packets.

• Routing is the process of determining the best path for data packets to travel from one network to another.

• Switching is the process of forwarding data packets within a network based on their destination MAC addresses.

• Routing protocols like OSPF and BGP are used to exchange routing information between routers.

• Switches use MAC address tables to determine the ...read more

Access ports are used to connect end devices, while trunk ports are used to carry traffic between switches.

• Access ports are assigned to a single VLAN and carry traffic for that VLAN only.

• Trunk ports can carry traffic for multiple VLANs using VLAN tagging.

• Access ports are typically used for devices like computers, printers, and IP phones.

• Trunk ports are used to interconnect switches or connect to network devices like routers or servers.

• An example of an access port configuratio...read more

MD5 hash is a cryptographic hash function used to verify data integrity and authenticity.

• MD5 hash generates a fixed 128-bit hash value from the input data

• It is commonly used to verify the integrity of files and messages

• MD5 hash is irreversible, meaning it cannot be decrypted back to the original data

• To use MD5 hash, a user can use a command-line tool or an online hash generator

Routing protocols determine how data packets are forwarded across a network, while routed protocols define the format of the packets.

• Routing protocols are used by routers to determine the best path for forwarding data packets.

• Examples of routing protocols include RIP, OSPF, and BGP.

• Routed protocols are used to format the data packets themselves, such as IP or IPv6.

• Examples of routed protocols include TCP/IP, UDP, and ICMP.

BGP stands for Border Gateway Protocol, used for routing between different autonomous systems on the internet.

• BGP is a standardized exterior gateway protocol used to exchange routing information between different autonomous systems (AS).

• It helps in determining the best path for data packets to travel between networks.

• BGP is crucial for ensuring efficient and reliable internet connectivity.

• It allows network administrators to control the flow of traffic and optimize network per...read more

Subnet mask is a 32-bit number used to divide an IP address into network and host portions.

• Subnet mask is used to determine which part of an IP address is the network portion and which part is the host portion.

• There are different types of subnet masks such as Classful subnet masks, Classless subnet masks, and Variable Length Subnet Masks (VLSM).

• Examples of subnet masks include 255.255.255.0 (Class C), 255.255.0.0 (Class B), and 255.0.0.0 (Class A).

OSPF is a link-state routing protocol used to exchange routing information within a single autonomous system. EIGRP is a Cisco proprietary routing protocol.

• OSPF stands for Open Shortest Path First

• It is a type of Interior Gateway Protocol (IGP)

• It uses Dijkstra's algorithm to calculate the shortest path

• EIGRP stands for Enhanced Interior Gateway Routing Protocol

• It is a Cisco proprietary protocol

• It uses a hybrid routing protocol that combines distance-vector and link-state routin...read more

BGP protocol is used for exchanging routing information between different autonomous systems on the internet.

• BGP stands for Border Gateway Protocol.

• It is an exterior gateway protocol used for inter-domain routing.

• BGP allows routers in different autonomous systems to exchange routing information.

• It helps in determining the best path for data packets to reach their destination.

• BGP is used by internet service providers (ISPs) to connect their networks and exchange routing inform...read more

Protocols are a set of rules that govern the communication between devices in a network.

• Protocols define the format and order of messages exchanged between devices.

• They ensure reliable and efficient communication by specifying how data is transmitted and received.

• Examples of protocols include TCP/IP, HTTP, FTP, DNS, and SMTP.

Yes, CCNA certified. EtherChannel is a technology used to combine multiple physical links into a single logical link for increased bandwidth and redundancy.

• EtherChannel is a Cisco proprietary technology used to bundle multiple physical links into a single logical link.

• It provides increased bandwidth and redundancy by load balancing traffic across the links.

• EtherChannel can be configured in different modes such as on, auto, desirable, or passive.

• It is commonly used in network ...read more

DORA process is the acronym for Discover, Offer, Request, and Acknowledge. It is a DHCP process used to assign IP addresses to devices on a network.

• Discover: The client sends a broadcast message to find available DHCP servers.

• Offer: The DHCP server responds with an IP address offer to the client.

• Request: The client requests the offered IP address from the DHCP server.

• Acknowledge: The DHCP server acknowledges the client's request and assigns the IP address.

A Network Engineer is responsible for designing, implementing, and maintaining computer networks.

• They configure and troubleshoot network hardware and software.

• They ensure network security and performance.

• They collaborate with other IT professionals to ensure network compatibility.

• They may specialize in areas such as wireless networking or network architecture.

• Examples of network engineer certifications include CCNA, CCNP, and JNCIA.

Switch operates at layer 2 of OSI model, forwarding data based on MAC addresses. Router operates at layer 3, forwarding data based on IP addresses.

• Switch operates at layer 2 of OSI model

• Switch forwards data based on MAC addresses

• Router operates at layer 3 of OSI model

• Router forwards data based on IP addresses

The ISO model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven layers.

• The ISO model stands for International Organization for Standardization model.

• It consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has specific functions and communicates with the adjacent layers for data transmission.

• For example, the Physical layer deals with the physical connec...read more

DHCP process involves four steps: Discover, Offer, Request, Acknowledge (DORA).

• Discover: Client broadcasts a DHCP Discover message to find available DHCP servers.

• Offer: DHCP server responds with a DHCP Offer message containing IP address lease information.

• Request: Client sends a DHCP Request message to request the offered IP address.

• Acknowledge: DHCP server sends a DHCP Ack message confirming the IP address lease to the client.

To configure SSID, access the wireless router's settings and enter the desired network name, security type, and password.

• Access the wireless router's settings through a web browser

• Locate the wireless settings section

• Enter the desired SSID (network name)

• Select the appropriate security type (WPA2, WEP, etc.)

• Set a strong password for the network

• Save the changes and restart the router if necessary

To upgrade firmware, you need to download the latest firmware version from the manufacturer's website and follow the specific instructions provided.

• Download the latest firmware version from the manufacturer's website

• Backup current configuration before upgrading

• Follow specific instructions provided by the manufacturer

• Test the new firmware in a controlled environment before deploying it in production

ACL stands for Access Control List and is used to control network traffic by allowing or denying packets based on defined rules.

• ACLs can be used to filter traffic based on source or destination IP address, protocol, port number, etc.

• They can be applied on routers, switches, and firewalls to control access to network resources.

• ACLs can improve network security by restricting unauthorized access to sensitive data.

• Example: An ACL can be configured on a router to block all incomi...read more

A firewall is a network security device that monitors and controls incoming and outgoing network traffic based on predetermined security rules.

• Firewall acts as a barrier between a trusted internal network and an untrusted external network.

• It examines network packets and filters them based on rules to allow or block traffic.

• Firewalls can be hardware-based or software-based.

• Examples of firewalls include Cisco ASA, Palo Alto Networks, and Windows Firewall.

A network is a group of interconnected devices that can communicate with each other. OSI model is a conceptual framework for network communication.

• Network is a collection of devices connected together to share resources and information.

• OSI model is a layered approach to network communication.

• It has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has a specific function and communicates with adjacent layers.

• Example: HTTP (Ap...read more

A router is a networking device that forwards data packets between computer networks.

• Routers operate at the network layer (Layer 3) of the OSI model.

• They use routing tables to determine the best path for data packets to reach their destination.

• Routers can connect multiple networks together, such as LANs and WANs.

• They provide network address translation (NAT) to allow multiple devices to share a single public IP address.

• Examples of routers include Cisco routers, Juniper router...read more

A VLAN (Virtual Local Area Network) is a logical grouping of devices on the same physical network, allowing for segmentation and improved network performance.

• VLANs are used to separate broadcast domains in a network.

• They can improve network security by isolating traffic between different VLANs.

• VLANs can be configured based on port, MAC address, or protocol.

• Example: VLAN 10 for finance department, VLAN 20 for marketing department.

BGP stands for Border Gateway Protocol, a routing protocol used to exchange routing information between different autonomous systems on the internet.

• BGP is used to make routing decisions based on network policies, rules, and paths.

• It is a path vector protocol that allows routers to share information about the best path to reach a certain destination.

• BGP operates on TCP port 179 and uses TCP connections to exchange routing information.

• BGP is classified into two types: eBGP (Ex...read more

Switching is the process of forwarding data packets between devices on the same network, while routing is the process of forwarding data packets between different networks.

• Switching operates at Layer 2 of the OSI model, using MAC addresses to forward packets within a network.

• Routing operates at Layer 3 of the OSI model, using IP addresses to forward packets between networks.

• Switches create broadcast domains, while routers create collision domains.

• Examples of switches include ...read more

NAT (Network Address Translation) is a process that allows multiple devices to share a single public IP address.

• NAT translates private IP addresses to public IP addresses and vice versa.

• It helps conserve public IP addresses and provides security by hiding internal network details.

• NAT can be implemented using different methods such as Static NAT, Dynamic NAT, and PAT (Port Address Translation).

• Example: When a user with a private IP address accesses the internet, NAT translates...read more

Router commands are used to configure and manage routers in a network.

• show ip interface brief - displays a summary of the router's interfaces and their IP addresses

• show running-config - displays the current configuration of the router

• interface [interface name] - enters interface configuration mode for a specific interface

• ip route [destination network] [subnet mask] [next hop IP] - adds a static route to the routing table

VLAN types include default, data, voice, management, and native VLANs.

• Default VLAN: VLAN 1 is the default VLAN on Cisco switches.

• Data VLAN: Used for data traffic.

• Voice VLAN: Used for voice traffic.

• Management VLAN: Used for managing network devices.

• Native VLAN: Untagged VLAN used for trunking.

Proxy is an intermediary server that separates end users from the websites they browse. DHCP is a network protocol that assigns IP addresses to devices.

• Proxy server acts as a middleman between a user and the internet, providing anonymity and security.

• DHCP dynamically assigns IP addresses to devices on a network, simplifying network administration.

• Proxy servers can be used to bypass content restrictions or improve network performance.

• DHCP servers can also provide additional ne...read more