Cognicel Consultancy Services Pvt Ltd, Interview Questions and Answers

Split horizon is a technique used in computer networking to prevent routing loops by not advertising routes back to the same interface they were learned from.

• Split horizon is used in distance-vector routing protocols like RIP to prevent routing loops.

• It works by not advertising routes back to the same interface they were learned from.

• Split horizon with poison reverse takes this a step further by advertising the route w...read more

BGP stands for Border Gateway Protocol, used to exchange routing information between different networks.

• BGP is an exterior gateway protocol used to make routing decisions on the internet.

• It operates by exchanging routing information between different autonomous systems (AS).

• BGP uses TCP port 179 for communication.

• BGP routers maintain a table of IP prefixes and their paths to reach them.

• BGP can be configured to influenc...read more

There are two types of BGP: eBGP and iBGP. eBGP has an AD value of 20, while iBGP has an AD value of 200.

• eBGP (External BGP) - AD value: 20

• iBGP (Internal BGP) - AD value: 200

Routing protocol is a set of rules used by routers to determine the best path for data packets to travel.

• Routing protocols help routers communicate with each other to dynamically update routing tables.

• Types of routing protocols include distance-vector (e.g. RIP), link-state (e.g. OSPF), and hybrid (e.g. EIGRP).

• Distance-vector protocols determine the best path based on hop count.

• Link-state protocols use a more complex a...read more

OSPF (Open Shortest Path First) is a routing protocol used to determine the best path for data packets in a network.

• OSPF is a link-state routing protocol

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

• OSPF routers exchange link-state advertisements (LSAs) to build a topology map

• It supports VLSM (Variable Length Subnet Masking) and CIDR (Classless Inter-Domain Routing)

• OSPF divides the network into areas to re

Preventing loop avoidance in BGP involves using loop prevention mechanisms like AS Path and Route Reflectors.

• Use AS Path attribute to prevent loops by tracking the path a route has taken through AS numbers.

• Implement Route Reflectors to avoid loops in BGP by controlling the route propagation within a cluster.

• Utilize BGP Confederations to divide the network into smaller autonomous systems to prevent loops.

• Regularly monit...read more

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

• The OSI model stands for Open Systems Interconnection model.

• It helps in understanding how data is transferred from one computer to another over a network.

• The seven layers of OSI model are: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has speci...read more

Traceroute is a network diagnostic tool used to track the path packets take from one networked device to another.

• Traceroute sends packets with increasing TTL values to determine the path to a destination.

• Each router along the path sends back an ICMP Time Exceeded message, allowing traceroute to map the route.

• The final destination sends an ICMP Port Unreachable message, indicating the end of the route.

• Traceroute helps i...read more

The presence of '*****' in a traceroute indicates that the router is blocking the ICMP packets used by traceroute.

• The '*****' indicates that the router is not responding to the ICMP packets sent by the traceroute tool.

• This could be due to the router being configured to block ICMP traffic for security reasons.

• It can also be caused by a firewall or network filtering rules blocking the ICMP packets.

• In some cases, the '***...read more

BGP states include Idle, Connect, Active, OpenSent, OpenConfirm, Established.

• Idle - Initial state when BGP is not yet established

• Connect - Attempting to establish a TCP connection

• Active - Waiting for a TCP connection to be completed

• OpenSent - Sent an Open message to peer

• OpenConfirm - Received an Open message and waiting for confirmation

• Established - BGP peers are fully established and can exchange routing information

The new router can be configured remotely using a laptop or mobile device with access to the network.

• Access the router's web interface by entering its IP address in a web browser

• Login using default credentials or credentials provided by the company

• Configure basic settings such as SSID, password, and security settings

• Update firmware if necessary

• Test the connection to ensure it is working properly

CE and PE routers are types of routers used in MPLS networks. CE routers connect to customer networks while PE routers connect to provider networks.

• CE routers (Customer Edge) connect to customer networks and are responsible for exchanging routes with customer devices.

• PE routers (Provider Edge) connect to provider networks and are responsible for exchanging routes with other PE routers in the MPLS network.

• CE routers are...read more

The command to assign an IP address on a Juniper router interface is 'set interface <interface_name> unit <unit_number> family inet address <ip_address/mask>'

• Use the 'set' command to configure the interface

• Specify the interface name and unit number

• Use the 'family inet' statement to configure an IPv4 address

• Specify the IP address and subnet mask

Parameters for BGP neighbourship include AS number, IP address, subnet mask, and BGP version.

• AS number must match on both neighbors

• IP address must be reachable between neighbors

• Subnet mask should be the same on both neighbors

• BGP version should be compatible between neighbors

tftp stands for Trivial File Transfer Protocol, a simple protocol used for transferring files over a network.

• tftp is a lightweight protocol used for transferring files between devices on a network.

• It operates on UDP port 69.

• tftp does not require user authentication, making it less secure compared to FTP.

• It is commonly used for booting devices over a network, such as in diskless workstations or routers.

• An example of tft...read more

Loop avoidance mechanism in BGP prevents routing loops by using loop prevention mechanisms like AS path attribute and route reflectors.

• BGP uses AS path attribute to prevent routing loops by not accepting routes with its own AS number in the path.

• Route reflectors are used in BGP to avoid loops in route propagation within a cluster of routers.

• BGP Confederations can also be used to prevent loops by dividing the AS into sm

Traceroute is a network diagnostic tool used to track the path packets take from source to destination IP.

• Traceroute sends packets with increasing TTL values to elicit ICMP Time Exceeded responses from routers along the path.

• The source IP is the IP address of the device initiating the traceroute, while the destination IP is the IP address of the target device.

• Traceroute displays the IP addresses of the routers in the p...read more

Public IP is the address assigned to a device that is directly accessible over the internet, while private IP is used within a private network.

• Public IP is unique and can be accessed from anywhere on the internet

• Private IP is used within a local network and is not directly accessible from the internet

• Public IP is assigned by the Internet Service Provider (ISP)

• Private IP addresses are typically in the ranges of 192.168.

To configure a router with support of a non tech guy onsite, provide step-by-step instructions and visual aids.

• Create a simple, easy-to-follow guide with step-by-step instructions.

• Use visual aids such as diagrams or videos to demonstrate the process.

• Provide clear explanations of each step and troubleshoot common issues.

• Offer remote support or a helpline for additional assistance if needed.

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

• Acts as a barrier between a trusted internal network and untrusted external network

• Filters network traffic based on rules set by the administrator

• Can be hardware-based or software-based

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

Routers connect multiple networks together while switches connect devices within a single network.

• Routers operate at the network layer (Layer 3) of the OSI model, while switches operate at the data link layer (Layer 2).

• Routers use IP addresses to forward data between networks, while switches use MAC addresses to forward data within a network.

• Routers can determine the best path for data to travel between networks, while...read more

MPLS stands for Multiprotocol Label Switching, a technique used in telecommunications networks to direct data packets along predefined paths.

• MPLS is used to improve network performance and efficiency by quickly routing data packets based on labels instead of IP addresses.

• It allows for traffic engineering, quality of service (QoS) prioritization, and virtual private network (VPN) services.

• MPLS operates at layer 2.5 of t...read more

FTP and TFTP are protocols used for transferring files over a network.

• FTP (File Transfer Protocol) is a standard network protocol used to transfer files from one host to another over a TCP-based network, such as the internet.

• TFTP (Trivial File Transfer Protocol) is a simpler version of FTP that uses UDP instead of TCP for file transfer.

• FTP requires authentication (username and password) for access, while TFTP does not ...read more