Saturday, October 6, 2018

What you should know before interviewing for a Network Administrator position

1. What is the difference between layer 2 and layer 3 in the OSI model?

Layer 2, the data link layer is responsible for moving frames from one(node) to the next. Whereas in layer 3 network layer is responsible for the delivery of individual packets from a source host to a destination host

2. What is a VLAN?

VLAN (Virtual Local Area Network) is a logical local area network (or LAN) that extends beyond a single traditional LAN to a group of LAN segments, given specific configurations. Since a VLAN is a logical entity, its creation and configuration are done completely in software.

3. What is the difference between TCP and UDP?

TCP is a reliable protocol. There is an acknowledgment for each TCP packet.
In UDP there are no acknowledgments. That means the sender does not know if a packet is received by the receiver.

4. How do you distinguish a DNS problem from a network problem?

if you are able to ping to a router or switch connected to DNS server but not able to ping DNS server..this is surely a problem with DNS....else its problem in the network.

5. Description of the OSI model?

Layer Name Description
Any application using the network, examples include
FTP and your web browser. HTTP.FTP.SMTP.DNS.RIP.SNMP

How the data sent is presented, examples
include JPG graphics, ASCII, and XML

For applications that keep track of sessions, examples
are applications that use Remote Procedure Calls (RPC)
like SQL and Exchange

Provides reliable communication over the network to make
sure that your data actually "gets there" with TCP being
the most common transport layer protocol. TCP. UDP

Takes care of addressing on the network that helps to
route the packets with IP being the most common
network layer protocol. Routers function at Layer 3.

Data Link
Transfers frames over the network using protocols
like Ethernet and PPP. Switches function at layer 2.

Controls the actual electrical signals sent over the
network and includes cables, hubs, and actual network links.

6. What is a runt, Giant, and a collision?

A runt is a packet in a network that is too small. For example, the Ethernet protocol requires that each packet be at least 64 bytes long. In Ethernet, which operates on the idea that two parties can attempt to get used of the line at the same time and sometimes do, runts are usually the fragments of packet collisions. Runts can also be the result of bad wiring or electrical interference. Runts are recorded by programs that use the Remote Network Monitoring (RNM) standard information base for network administration

A giant is a packet, frame, cell, or other transmission units that is too large. Network protocols specify maximum and minimum sizes (and sometimes a single uniform size) for any transmission unit. For example, ATM packages all data into 53-byte cells. Any cell larger than that is discarded and recorded as a giant by network monitoring tools

A collision is a result when the two devices on the same Ethernet network attempting to send their data exactly at the same time

7. What is a broadcast storm?

A broadcast storm occurs when a network system is overwhelmed by continuous multicast or broadcast traffic. When different nodes are sending/broadcasting data over a network link, and the other network devices are rebroadcasting the data back to the network link in response, this will eventually cause the whole network to meltdown and lead to the failure of network communication.

8. What is the purpose of VRRP?

Virtual Router Redundancy Protocol (VRRP) is a non- proprietary redundancy protocol described in RFC 3768 designed to increase the availability of the default gateway servicing hosts on the same subnet.

9. What is a VPN?

10. What is a default route?

A default route, also known as the gateway of last resort, is the network route used by a router when no other known route exists for a.

11. How do you set a default route on an IOS Cisco router?



ROUTER#conf t 

ROUTER(config)# ip route insert gateway address here 



11. What is a metric?

12. What is a MAC address?

A Media Access Control address (MAC address) is a unique identifier assigned to network interfaces for communications on the physical

13. What is ARP/RARP?

What is it for:  Arp translates IP numbers into hardware addresses.

How ARP works:  Send a packet from the querying host with an Ethernet broadcast address asking the target host with the given IP address to respond.  All hosts on the physical network receive this packet, and the one with the given IP number responds.  Then the original querying host knows the physical address of the target host.   Does not use IP; uses's physical frames.

RARP - Reverse Address Resolution Protocol

What is it for:  Diskless clients don't have a place to store their IP number.  Rarp translates machines addresses into IP numbers.

How RARP works:  The client broadcasts a RARP packet with an ethernet broadcast address, and it's own physical address in the data portion.  The server responds by telling the client it's IP address.  Note there is no name sent.  Also, note there is no security.  Does not use IP; uses's physical frames.

14. Describe a TCP connection sequence

The connection establishment process actually accomplishes several things as it creates a connection suitable for data exchange: Contact and Communication: The client and server make contact with each other and establish communication by sending each other messages. The server usually doesn't even know what client it will be talking to before this point, so it discovers this during connection establishment. o Sequence Number Synchronization: Each device lets the other know what initial sequence number it wants to use for its first transmission.

15. What is IPv6?

Internet Protocol Version 6 (IPv6) is a version of the Internet Protocol that is designed to succeed Internet Protocol version 4 (IPv4),...In comparison, IPv6 addresses are 128 bits, which allow for approximately three hundred and forty trillion, trillion unique IP addresses. An example IPv6 address is:

16. What is a server exchange?

Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure products. Exchange's major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage.

17. What is MTU?

In computer networking, the maximum transmission unit (MTU) of a communications protocol of a layer is the size (in bytes) of the largest protocol data unit that the layer can pass onwards.
What other TCP setting can you modify besides MTU to shorten packets?


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