Sunday, July 13, 2008

TECHNICAL QUESTIONS FOR INTERVIEW

These questions are not intended to grill a person, they are to find out how much someone knows and how they deal with answering questions to which they may have no idea as to the answer. They provide a means to see how a person reacts and if they don't know the answer how they deal with being told the answer. Usually nasty interview type stuff.

To some questions there is no wrong answer, just degrees of being right.

Networking Questions:

What are the 3 major classes of IP network? A, B, C, D, E

What is a Class D IP address Multicast Addresses?

What addresses do multicast start with? 224.0.0.0

What is OSPF?
Open Shortest Path First. A routing protocol which supports the concept of a "core" area to which everything attach├ęs. Enforces a structure to the routed network.

What is BGP?
Border Gateway Protocol. Currently version 4. BGP is used for routing between networks on the Internet core, it supports many advanced routing features.

Define an autonomous system?
An autonomous system is a community of interest. Used in conjunction with routing protocols it breaks up parts of the network into manageable chunks.

What does the Ether type code do?
It differentiates which protocol the ethernet frame is carrying.

How would you configure a three-router network with an Internet connection? Default routes, ip classless, ISDN or Frame Relay, no wrong answers.

Dial on demand
Dial on demand is a "technology" which only activates network connection when "interesting" packets are to be sent across the infrastructure.

How many bytes in an IPX network address?
An IPX address is made up of 4 bytes of Network address and 6 bytes of node address and takes the form of ABABABAB.FFFF.FFFF.FFFF. The address is in hexadecimal. The network address is allocated by the network (usually the servers or routers) and the node address is the MAC address of the device.
What mask would you use to super net two class C addresses 255.255.254.0,
the first address must be even, i.e. 203.14.2.0 with the mask of 255.255.254.0 makes a network of 203.14.2.0 - 203.14.2.255.

What is LANE? Why is it necessary?
LAN Emulation used to run normal networking over ATM, it emulates the broadcast nature of a LAN over connection oriented ATM.

What is VLANing?
Virtual LAN is used on large LANs to break up the network into smaller Broadcast Domains. This creates communities of interest. These communities can be based around organizational structures or

How do you spell FDDI?

What is CIDR?
Classless Internet Domain Routing, used in conjunction with Classless routing protocols to summarize the Internet into smaller routing tables.

What is VLSM?
Variable Length Subnet Mask, used to allocate the amount of address space required by the end network.

What IP protocol does DLSW use?
TCP. Connection oriented and reliable.

What IP port number does DLSW use?
It uses a series of port numbers to allow priotisation. The primary port is 2065. Others are:
high 2065
medium 1981
normal 1982
low 1983

Questions from Andrew Latta:

1. Please outline your practical experience in terms of the:

- design,

- installation,

- maintenance,

- performance monitoring, and

- fault detection and resolution

Of telecommunications hardware in a LAN/WAN environment.

2. What factors do you believe are important in managing an Australia wide telecommunications network on a day-to-day basis?

- appropriate staffing levels and budget

- appropriately trained staff

- clear corporate plan

- clear strategies to meet the plan

- proper reporting lines (both up and down)

- KPI's (Key Performance Indicators) to measure effectiveness by

- adequate system monitoring and alarms

- adequate diagnostic tools (possibly operated remotely)

- adequate support staff in remote sites

- be responsive to the needs and wishes of the user base

- collect performance statistics

- maintain a fault log

- document every change

- be familiar with emerging technologies

- capacity planning

3. What sort of factors should you consider when developing an Australia wide telecommunications network?

- open systems philosophy

- non-proprietary standards based architecture

- development of engineering standards to be applied throughout

- development of standard performance reports (e.g. for use in capacity planning)

- development of a fault recording and reporting system

- development of procedures and policies for dealing with fault identification and service restoration

- development of documentation standards and periodic reviews

- adherence to development methodology when enhancing or developing services (eg. SDM)

- adherence to current purchasing policy

- appropriate training schedule for staff

4. User(s) are complaining of delays when using the network. What would you do?

- get the user(s) to demonstrate the problem

- determine how many other users are affected

- ensure desktop hardware and configuration is OK

- trace all connections (they may be on another subnet)

- commence some monitoring or diagnostics

- determine problem (if there is one)

- provide solution

5. What are some of the problems associated with operating a switched LAN?

- It segments a LAN into separate collision domains, but not broadcast domains.

- performance monitoring is difficult, as a monitoring agent is required in each segment, or on the switch, but must be capable of monitoring each segment individually. In practice, the overhead required in the switch to provide all 9 groups of RMON is prohibitive, so manufacturers offer a subset of RMON groups only. The other means of obtaining full RMON information is to have a dedicated probe, and use "port steering" or "port mirroring" to obtain data for each port.

- Incorrect deployment of a switch can lead to response time problems (e.g. if switches are put in the place of hubs in a collapsed backbone topology).



6. Name some of the ways of combining TCP/IP traffic and SNA traffic over the same link.

-DLSw (Data Link Switching)(aka RFC1434)

-RFC1490 (frame relay carrier)

- Serial Tunneling (STUN)

- BAN or BNN (Boundary Access Node, Boundary Network Node)

7. Your staff is all working on several problems affecting several users, and you receive a call that there is a problem affecting many users at a remote site. What would you do?

- attend to the problem yourself

- redeploys one of your staff from their current task (thus servicing the problem affecting the most number of users first, as it is typically more serious)

8. What are the differences between a meshed and a star topology? Describe some of the advantages and disadvantages of each in a WAN context.

meshed - redundant paths, links to all sites in matrix from all sites in matrix, more complex, more fault tolerant, harder to configure

star - individual link from core to each site, response time better, straightforward, no redundancy, easy to configure

9. What sort of factors would you take into account in calculating utilization levels on a link?

- the calculation is ultimately dependant on the available bandwidth of the link in question

- the total number of packets sent and received over the link (usually derived from packets in/out of a router port)

- the time span involved

10. What is the essential difference between primary rate (Macro link) and basic rate (Micro link) interfaces on an ISDN service?

PRI - 30 B + 1 D channel

BRI - 2 B + 1 D channel



11. What advantages does Fame Relay have over ISDN as a carrier service?

- ability to have PVC's connected anywhere in the cloud

- ability to burst over usual rate (CIR)

- cheaper than ISDN, provided CIR appropriately sized

- resizing of CIR's and changing PVC's can be done immediately

- only pay for the capacity you use

12. What sort of cabling is suitable for Fast Ethernet protocols?

cat 5 UTP

Optic Fibre

13. What are the minimum and maximum sizes of packets in an 802.3 Ethernet protocol?

minimum - 64bytes

maximum - approx1500 bytes (actually 1518 bytes)

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