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

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

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.

STP is a network protocol that prevents loops in Ethernet networks. VLANs divide a network into separate broadcast domains. DHCP assigns IP addresses, DNS resolves domain names. OSI model defines networking functions in layers.

• STP (Spanning Tree Protocol) prevents loops by blocking redundant paths in a network.

• VLAN (Virtual Local Area Network) divides a network into separate broadcast domains to improve network performance and security.

• DHCP (Dynamic Host Configuration Protoco...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 '.

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

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

Troubleshooting DHCP issues involves checking configurations, connectivity, and logs to ensure proper IP address assignment.

• Verify DHCP server is running and reachable. Example: Use 'ping' to check server connectivity.

• Check DHCP scope and ensure there are available IP addresses. Example: Use 'show ip dhcp binding' on Cisco devices.

• Inspect client configurations for correct DHCP settings. Example: Ensure clients are set to obtain IP automatically.

• Review DHCP logs for errors or ...read more

Routing involves forwarding data packets between networks, while switching involves forwarding data packets within a network.

• Routing is the process of determining the best path for data packets to travel from source to destination across different networks.

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

• OSPF (Open Shortest Path First) is a routing protocol used to find the best path for data packets in IP networks.

• BGP (Border Gatewa...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

Control plane manages routing decisions, data plane handles traffic, and management plane oversees network operations.

• Control Plane: Responsible for routing and signaling; e.g., OSPF, BGP protocols.

• Data Plane: Forwards user data packets; e.g., switches and routers processing traffic.

• Management Plane: Manages network devices and configurations; e.g., SNMP, network management systems.

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

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 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.

DNSB server stands for DNS-Based Blackhole server. It is used to block access to malicious websites.

• DNSB server is a type of DNS server that blocks access to websites based on their domain name or IP address.

• It is commonly used to prevent access to malicious websites that may contain malware or phishing scams.

• DNSB servers can also be used to block access to specific categories of websites, such as gambling or adult content.

• DNSB servers work by intercepting DNS requests and re...read more

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.

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

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

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

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