700+ Network Engineer Interview Questions and Answers

Questions related to TCP/IP layers, subnet mask, VLAN, ARP, port number, IP and MAC addresses.

• Transport layer is needed for reliable communication and error correction.

• Subnet mask is used to identify the network and host portions of an IP address.

• VLAN is needed for network segmentation and security.

• Switches and routers send packets or frames based on destination IP address.

• Types of ARP include ARP request and ARP reply.

• Port number is used to identify the application or servic...read more

MPLS is a protocol used to efficiently route network traffic by assigning labels to packets.

• MPLS stands for Multiprotocol Label Switching

• It is used to improve network performance and reduce congestion

• LDP (Label Distribution Protocol) is used to distribute labels to network devices

• CEF (Cisco Express Forwarding) is a fast switching technology used in MPLS networks

• MP-BGP (Multiprotocol Border Gateway Protocol) is used to exchange routing information between different autonomous ...read more

STP (Spanning Tree Protocol) is a network protocol that prevents loops in Ethernet networks. It elects a root bridge to manage the network.

• STP is a network protocol used to prevent loops in Ethernet networks.

• It works by creating a loop-free logical topology by blocking redundant paths.

• STP elects a root bridge, which becomes the central point of the network.

• The root bridge is the bridge with the lowest bridge ID.

• STP uses Bridge Protocol Data Units (BPDUs) to exchange informati...read more

BGP is a routing protocol used to exchange routing information between different autonomous systems. It uses path vector algorithm.

• Split horizon rule prevents a router from advertising a route back to the same interface from which it was learned.

• BGP route reflector is configured by defining a cluster ID and selecting reflector clients.

• BGP path selection algorithm selects the best path based on attributes like AS path length, origin code, MED, etc.

• EBGP multihop concept is used...read more

LAN stands for Local Area Network, which connects two or more devices in a limited area.

• LAN is a type of network that connects devices within a limited area such as a room, floor, or building.

• It allows devices to communicate with each other and share resources such as printers and files.

• LAN can be wired or wireless, and can be set up using Ethernet cables or Wi-Fi.

• Examples of LAN include home networks, office networks, and school networks.

The question covers various networking concepts and protocols such as STP, EIGRP, OSPF, TCP header, and IOS commands.

• STP (Spanning Tree Protocol) is used to prevent loops in a network.

• EIGRP (Enhanced Interior Gateway Routing Protocol) dual algorithm is a routing protocol used in Cisco networks.

• Static Routing is a type of routing where the network administrator manually configures the routes.

• Administrative Value is a numerical value assigned to different routing protocols to d...read more

Answers to questions related to Network Engineer job interview

• GSM module is a hardware device that enables communication between mobile devices and cellular networks

• The architecture of GSM module consists of a SIM card, a microcontroller, a power supply, and a radio transceiver

• GSM module uses digital signal

• ADC stands for Analog to Digital Converter and DAC stands for Digital to Analog Converter

• Python is a high-level programming language used for web development, data analysis...read more

NAT is a technique used to map private IP addresses to public IP addresses. Port numbers are used to identify specific applications.

• NAT stands for Network Address Translation

• It is used to allow devices with private IP addresses to access the internet using a public IP address

• Port numbers are used to identify specific applications or services

• Common port numbers include 80 for HTTP, 443 for HTTPS, and 22 for SSH

VTEP is a virtual tunnel endpoint and VXLAN is a network overlay technology used for scaling out virtualized data centers.

• VTEP is used to encapsulate and de-encapsulate VXLAN packets.

• VXLAN is used to extend Layer 2 segments over a Layer 3 network.

• VXLAN is used in ACI to provide a scalable and flexible network fabric for multi-tenant environments.

• VXLAN allows for up to 16 million unique network segments.

• VXLAN uses a 24-bit segment ID to identify the virtual network.

• VXLAN packe...read more

Leaf and Spine architecture is used in data center networks for scalability and redundancy. Fabric mode is used for efficient communication between them.

• Leaf and Spine architecture is a two-tier network design where leaf switches connect to spine switches.

• Leaf switches are connected to servers and storage devices while spine switches connect to other switches.

• This architecture provides high bandwidth, low latency, and redundancy.

• Fabric mode is used to create a single logical ...read more

Private IP addresses ranges are reserved for internal networks and not routable on the internet.

• Private IP addresses are used within a local network and are not accessible from the internet

• There are three ranges of private IP addresses: 10.0.0.0 - 10.255.255.255, 172.16.0.0 - 172.31.255.255, and 192.168.0.0 - 192.168.255.255

• Private IP addresses are commonly used in home and office networks to allow devices to communicate with each other

A ticket can be managed by following a systematic approach.

• Acknowledge the ticket and assign it to the appropriate team member

• Set a priority level based on the severity of the issue

• Communicate with the customer and provide regular updates

• Resolve the issue and close the ticket

• Document the entire process for future reference

ACI stands for Application Centric Infrastructure. It is a software-defined networking solution by Cisco.

• ACI provides centralized automation and policy-driven application profiles.

• It enables network administrators to manage the entire infrastructure as a single entity.

• ACI supports multi-tenancy, security, and integration with third-party tools.

• It uses a declarative model to define application requirements and automatically configures the network accordingly.

• ACI includes a har...read more

Multiplexer is a device that combines multiple signals into one signal. Demultiplexer is a device that separates one signal into multiple signals.

• Multiplexer is also known as MUX.

• It is used to increase the capacity of a communication channel.

• Demultiplexer is also known as DEMUX.

• It is used to route a single input signal to multiple output signals.

• Multiplexer and demultiplexer are commonly used in digital communication systems.

• Example: A 4:1 MUX can combine four input signals i...read more

Trunk is used to carry multiple VLANs between switches, while access is used to connect end devices to the network.

• Trunk is used to connect switches together and carry multiple VLANs

• Access is used to connect end devices like computers, printers, etc. to the network

• Trunk ports are configured with VLAN tagging, while access ports are not

• Examples of trunk ports are inter-switch links, while examples of access ports are ports connected to end devices

VDC is Virtual Device Context. One supervisor can create up to 4 VDCs.

• VDC allows multiple virtual switches to be created on a single physical switch

• Each VDC has its own set of interfaces, VLANs, routing tables, and management interfaces

• VDCs provide better resource utilization and isolation between different network services

The IP phone boot up process involves several steps to initialize the device and connect to the network.

• The phone powers on and performs a self-test

• It obtains an IP address from the DHCP server

• It downloads the firmware and configuration files from the TFTP server

• It registers with the call manager or PBX

• It is ready to make and receive calls

The show interface command displays the status and statistics of a network interface.

• Displays the interface type, member, module, and number

• Shows the current status of the interface (up or down)

• Displays the number of packets transmitted and received

• Shows the number of errors and discards

• Displays the speed and duplex settings of the interface

Questions related to networking concepts and technologies.

• TCP/IP model is a conceptual model used to describe the communication protocols used on the internet.

• STP (Spanning Tree Protocol) is used to prevent loops in a network by blocking redundant paths.

• Routing is the process of finding the best path for data to travel from one network to another, while switching is the process of forwarding data within a network.

• OSPF (Open Shortest Path First) is a routing protocol used to d...read more

Identifying OSPF cost, BGP attributes, and STP working

• OSPF cost is calculated based on the bandwidth of the link

• BGP attributes include AS path, next hop, local preference, etc.

• STP works by selecting a root bridge and blocking redundant paths

• OSPF cost can be manually configured using the 'ip ospf cost' command

• BGP attributes are used to determine the best path for routing

• STP uses BPDU messages to exchange information and build a loop-free topology

NSSA area is a type of OSPF area that allows external routes to be injected into the OSPF domain.

• NSSA stands for Not-So-Stubby-Area.

• It is used when an area needs to import external routes but still wants to maintain some level of stubbiness.

• NSSA area has an ABR (Area Border Router) that translates Type 7 LSAs (Link State Advertisements) into Type 5 LSAs.

• Type 7 LSAs are generated by ASBR (Autonomous System Boundary Router) in the NSSA area.

• NSSA area can be used in scenarios wh...read more

BGP (Border Gateway Protocol) is a routing protocol used in internet networks. It provides scalability, redundancy, and policy control.

• BGP is used to exchange routing information between different autonomous systems (AS)

• It allows for efficient routing decisions based on policies and network conditions

• BGP states represent the different stages of establishing and maintaining BGP peering sessions

• Examples of BGP states include Idle, Connect, Active, OpenSent, OpenConfirm, Establi...read more

Traffic forwarding between EPGs on the same leaf is achieved through VXLAN encapsulation and routing protocols.

• VXLAN encapsulation is used to create a virtual overlay network that spans multiple physical leaf switches.

• Routing protocols such as OSPF or BGP are used to exchange routing information between the leaf switches.

• The end point user's traffic is encapsulated in a VXLAN packet and forwarded to the destination leaf switch, where it is decapsulated and forwarded to the de...read more

VPC stands for Virtual Private Cloud. It is a virtual network that provides a secure and isolated environment within the public cloud.

• VPC domain is a logical boundary within which resources are created and managed.

• VPC allows multiple virtual machines to communicate with each other as if they were on the same physical network.

• VPC provides high availability and fault tolerance by allowing multiple instances to be deployed across multiple availability zones.

• VPC also allows for t...read more

Network topology is created by designing the layout of network devices and connections. Types include star, bus, ring, mesh, and hybrid.

• Identify network requirements and goals

• Select appropriate topology based on needs (e.g. star for centralized control, mesh for redundancy)

• Design layout of network devices and connections

• Implement network topology using physical or virtual components

• Test and optimize network performance

BGP is a routing protocol used to exchange routing information between different networks.

• BGP stands for Border Gateway Protocol.

• It is used to connect different autonomous systems (AS) on the internet.

• BGP uses path vector routing to determine the best path for data to travel.

• BGP attributes include AS path, next hop, local preference, and origin.

• AS path is a list of AS numbers that the route has passed through.

• Next hop is the IP address of the next router in the path.

• Local pre...read more

Cisco 920 series routers are designed for small to medium-sized businesses, while Cisco 903 series routers are designed for enterprise-level networks.

• Cisco 920 series routers are more cost-effective for smaller businesses with fewer network requirements.

• Cisco 903 series routers offer higher performance and scalability for larger, more complex networks.

• Cisco 920 series routers may have fewer ports and features compared to Cisco 903 series routers.

• Cisco 903 series routers are t...read more

Fiber media connectivity uses optical fibers for data transmission, while MW media connectivity uses microwave signals.

• Fiber media connectivity uses optical fibers to transmit data through light signals

• MW media connectivity uses microwave signals to transmit data through the air

• Fiber connectivity offers higher bandwidth and longer distance transmission compared to MW connectivity

• Fiber connectivity is more secure and immune to electromagnetic interference compared to MW connec...read more

Network protocols are rules and conventions for communication between devices on a network.

• Network protocols define how data is formatted, transmitted, received, and acknowledged in a network.

• Commonly known protocols include TCP/IP, HTTP, FTP, and DNS.

• TCP/IP is a suite of protocols that governs how data is transmitted over the internet.

• HTTP is used for transferring hypertext documents on the World Wide Web.

• FTP is used for transferring files between a client and a server.

• DNS r...read more

BGP routing tables store information about routes to different networks and the best path to reach them.

• BGP uses a path-vector routing protocol to determine the best path for a packet to reach its destination.

• BGP routing tables contain information about the network prefixes, the next hop to reach them, and the path attributes that determine the best path.

• BGP routers exchange routing information with their neighbors to build and maintain their routing tables.

• BGP routing tables...read more

The service that needs to run to connect to other unified communication applications is the Session Initiation Protocol (SIP).

• Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, modifying, and terminating real-time sessions involving video, voice, messaging, and other communications applications.

• SIP is commonly used in Voice over IP (VoIP) systems and allows for the establishment and control of multimedia communication sessions.

• By runni...read more

A network is a group of interconnected devices that communicate with each other to share resources and information.

• A network can be wired or wireless

• Devices on a network can include computers, printers, routers, and switches

• Networks can be local (LAN) or wide area (WAN)

• Switches are devices that connect devices on a network and direct traffic between them

ARP is a protocol used to map an IP address to a MAC address. It detects different networks by comparing the IP address and subnet mask.

• ARP stands for Address Resolution Protocol

• It maps an IP address to a MAC address

• It works by broadcasting an ARP request to all devices on the network

• The device with the matching IP address responds with its MAC address

• If the destination device is in a different network, ARP compares the IP address and subnet mask to determine this

The range of private IP addresses is defined by three blocks: 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255.

• Private IP addresses are used within private networks and are not routable on the internet.

• The three blocks of private IP addresses are reserved for use in local area networks (LANs) and are not unique globally.

• Private IP addresses allow organizations to have multiple devices with the same IP addresses within their private ...read more

A network engineer interview question covering topics like DDOS, VLAN, VTP, access and trunk ports, Intervlan routing, and traceroute/MTR.

• DDOS stands for Distributed Denial of Service, which is a type of cyber attack that floods a network or server with traffic to make it unavailable to users.

• TCPDUMP is a command-line packet analyzer that can capture and display network traffic. It can be used to identify the source and type of traffic during a DDOS attack.

• VLAN stands for Vir...read more

Technical skills often require specific education, such as programming languages, technical writing, or data analysis.

• Programming languages: Examples include Java, Python, C++, etc.

• Technical writing: Ability to write technical documentation, manuals, and reports.

• Data analysis: Skills in analyzing and interpreting data using tools like Excel, SQL, or R.

Bridge domain is a layer 2 construct that separates broadcast domains. VNI is a VXLAN Network Identifier used for overlay networking.

• Bridge domain is used to isolate traffic within a specific VLAN or subnet.

• VNI is a 24-bit identifier used to identify VXLAN segments in an overlay network.

• Both bridge domain and VNI are layer 2 constructs used in network virtualization.

• Bridge domain is not a protocol, but VNI is a protocol used in VXLAN.

• Bridge domain and VNI are commonly used in...read more

BGP, EIGRP, and ISIS are routing protocols used in networking.

• BGP (Border Gateway Protocol) is used for routing between different autonomous systems.

• EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary protocol used for routing within a single autonomous system.

• ISIS (Intermediate System to Intermediate System) is a protocol used for routing within a single autonomous system, similar to EIGRP.

• BGP uses a path-vector algorithm to determine the best path for ...read more

Logs should be taken from the network devices involved in the call flow.

• Check logs on the caller's iPhone

• Check logs on the recipient's iPhone

• Check logs on the network devices (routers, switches) involved in the call flow

• Look for any error messages or anomalies in the logs

• Analyze the logs to identify any network issues or misconfigurations

ACI provides connectivity to the internet through external Layer 3 networks.

• ACI uses external Layer 3 networks to connect traffic to the internet.

• This is achieved through the use of Border Gateway Protocol (BGP) and External Routing Policies (ERPs).

• ACI also supports the use of Network Address Translation (NAT) to translate internal IP addresses to external IP addresses.

• ACI can be configured to use multiple external Layer 3 networks for redundancy and load balancing.

• ACI also p...read more

The subnet mask for CIDR /29 is 255.255.255.248.

• CIDR /29 means 29 bits are used for the network portion and 3 bits for the host portion.

• To calculate the subnet mask, convert the 29 network bits to 1s and add 3 0s for the host bits.

• The result is 255.255.255.248 in dotted decimal notation.

To check port and duplex setting, MSS and MTU, and link utilization in network engineering.

• Use command 'show interface' to check port and duplex setting.

• Use command 'ping -f -l ' to check MTU.

• Use command 'netstat -s' to check MSS.

• Use command 'show interface' or 'show interfaces utilization' to check link utilization.

DNS is a system that translates domain names into IP addresses. DHCP is a protocol for assigning IP addresses. IP address is a unique identifier for devices. RJ-45 is a type of connector used for Ethernet cables.

• DNS translates domain names (e.g., www.example.com) into IP addresses (e.g., 192.168.1.1).

• DHCP is a protocol that automatically assigns IP addresses to devices on a network.

• An IP address is a numerical label assigned to each device connected to a computer network.

• RJ-4...read more

IPG refers to Interface Profile Group which is used to group interface profiles. Interface policies define the behavior of interfaces.

• IPG is used to group interface profiles together for easier management.

• Interface policies define the behavior of interfaces such as QoS, security, and VLAN settings.

• IPG can be used to apply interface policies to multiple interfaces at once.

• For example, you can create an IPG for all access ports and apply an interface policy for VLAN settings to...read more

OSPF is a routing protocol used to exchange routing information between routers in a network.

• OSPF stands for Open Shortest Path First

• It is a link-state routing protocol

• OSPF uses LSAs (Link State Advertisements) to exchange routing information

• There are 5 types of LSAs: Router LSA, Network LSA, Summary LSA, ASBR Summary LSA, and External LSA

• Each LSA type serves a different purpose in the OSPF network

• OSPF is commonly used in large enterprise networks

Overlay is a network virtualization technique that adds a layer of abstraction over the physical network, while underlay refers to the physical network infrastructure.

• Overlay is used to create virtual networks on top of the physical network infrastructure.

• Underlay refers to the physical network infrastructure that provides connectivity between devices.

• Overlay networks are used to provide network virtualization, multi-tenancy, and network segmentation.

• Underlay networks are res...read more

Check for alternate path, isolate the failed link, replace the link or switch.

• Check for alternate path in the ring topology

• Isolate the failed link by disabling it

• Replace the failed link or switch

• Verify connectivity and network stability