IT Consultant Interview Questions and Answers by rafomac

Layers of the OSI model:

Physical

Data

Network

Transport

Session

Presentation

Application

Ports:

SMTP 25

LDAP 389

POP3 110

IMAP 143

RDP 3389

Class Ranges:

A 1 -126

B 128 -191

C 192 -223

D 224 -239

E 240 -255

Purpose of:

DNS  -Maps URL to IP

DHCP - Reservation system for IP

Can you write SQL queries?

-Answer is up to you

RAID 0 - Also known as Stripe Set. Data is split evenly across 2 or more disks without Parity Information

RAID 1 -Mirroring

RAID 5 - Uses block-level striping with parity data distributed across all member disks

Interviewer: What is a default Route?

-Well a default route is the route that a packet will take when no other routes are specified in the Routers route table.

Describe the 7 layers of the
OSI model 

Physical - The physical layer consists of the basic networking hardware transmission technologies of a network.
Data Link - MAC responsible for media access control, flow control and error checking

Network - (IP) The network layer is responsible for packet forwarding including routing through intermediate routers

Transport - (TCP/UDP) the Transport layer ensures the reliable arrival of messages and provides error checking mechanisms and data flow controls


Session - This layer establishes, manages and terminates connections between applications.


Presentation - This layer formats and encrypts data to be sent across a network. Works by transforming data into a format that can be accepted by the Application Layer.

Application This layer supports application and end-user processes. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely in the application level. Tiered application architectures are part of this layer.

Explain what an OSPF area.

- Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks.

-An OSPF network may be structured, or subdivided, into routing areas to simplify administration and optimize traffic and resource utilization.

Explain what happens when a device comes onto the network and requests a DHCP lease

-The clients request configuration settings using the DHCP protocol such as an IP address, a default route and one or more DNS server addresses. Once the client implements these settings, the host is able to communicate on that internet. DHCP provide IP address automatically.

Describe IP Sec

-Internet Protocol Security = IPSec is a technology protocol suite for securing Internet Protocol (IP) communications by authenticatingand/or encrypting each IP packet of a communication session.

Describe IKE phase 1 and phase 2

-Internet Key Exchange (IKE and IKEv2) Is the key to setup a Security Association (SA) which is a shared security attribute between two network entities to support secure communication, such as cryptographic alogorithm and mode, traffic encryption key, and parameters for the network data to be passed over the connection.

 Explain what a VLAN is

-Network architects set up VLANs to provide the segmentation services traditionally provided only by routers in LAN configurations. 

-VLANs address issues such as scalability, security, and network management

Explain a trunk port

-Trunks are used to interconnect switches to form networks, and to interconnect local area networks (LANs) to form wide area networks (WANs) or virtual LANs (VLANs). 

-These ports are capable of carrying traffic for any and ALL VLANs accessible by a switch 

Explain an access port

-In contrast to a trunk port which carries traffic to all VLANs an access port carries traffic to and from the specific VLAN assigned to it

Explain what a spanning tree protocol is

-So the Spanning Tree Protocol (STP) is a network protocol that ensures a loop-freetopology for any bridged Ethernet local area network.

What is the root bridge?

-The root bridge of the spanning tree is the bridge with the smallest (lowest) bridge ID. Determined by the Bridge ID and the MAC address

Describe how a switch determines how to send a packet to its destination

-Well a switch which exists at Layer 2 uses the media access control address (MAC address) from the host's network interface cards (NICs) to decide where to forward frames