IP/PS Engineer Entry Level Technical Interview Questions & Answers
Sometime back, the company I worked for asked me to help and prepare a technical assessment to be used by HR in headhunting for an entry level IP/PS Core network engineer. In most telecom companies, the IP and PS roles are combined especially if the company is small or mid-sized. Having so far spent about 10 years working in IP/PS operations, I thought these questions were fair and relevant, please let me know what you think by commenting on this article.
[Note: Answers are in italic format]
Section A: IP Questions & Answers
What is the difference between a private IP address and a public IP address? Give examples of where these two categories are applicable.
- Private IP address – These are addresses which are NOT routable on the internet.
- Public IP address – These are addresses which are routable on the internet.
With reference to the OSI model, at what layer would you place the following devices?
- A Switch – Layer 2 (Data Link)
- A Router – Layer 3 (Network Layer)
- A Firewall – Layer 3 and Layer 4
What do you understand by the term VLSM? And why is it so important in IP address planning and management?
VLSM – Variable Length Subnet Masking
VLSM is a technique used by network planners to effectively manage and save IP space. Using VLSM technique you can be able to use a subnet mask of varying length to break down a network address into different subnets of different sizes. This allows a planner to assign just enough addresses as required by different network sizes.
What is OSPF? And briefly explain why it is important do divide your OSPF network into multiple areas?
OSPF – Open Shortest Path First
Areas in OSPF help in reducing the routing table size and the LSDB (Link State DataBase) size hence reducing the time required for network convergence and also saving on system resources like the router CPU which is used to run the SPF algorithm.
Define MPLS and tell us the main difference between MPLS and the usual interior routing protocols like OSPF?
MPLS – Multi Protocol Label Switching
OSPF – Open Shortest Path First
MPLS uses labels to switch/route packets as opposed to OSPF which uses the IP address in the packet header to route packets to the destination. When a packet enters an MPLS domain, a label is added, this label is what is used to guide the packet through the MPLS domain. When a packet enters an IP routing domain say (OSPF), the routers use the IP address information contained in the packet header to guide the packet to the next hop/destination.
What is a VLAN? And what protocol standard is used for VLAN encapsulation?
VLAN – Virtual Local Area Network
VLAN uses protocol standard 802.1Q for encapsulation
What do you understand by the technique NAT? and why is NAT so important in IP networks?
NAT – Network Address Translation
NAT is a technique that allows multiple private addresses to use one or a few public addresses to access the internet.
This technique was developed to save on the scarce public IP space.
What are some of the parameters that you can use to effectively measure performance of an IP transmission PATH?
- Latency – Also known as packet delay is measured in milliseconds and it’s the time it takes for a packet to move from a source to a destination and back to the source (round trip)
- Jitter – this is the delta in packet delay
- Packet Loss – This a percentage of the number of packets received on an IP Path (round-trip) to the total number of packets transmitted on that IP Path.
Cyber Security Researcher
5 年Good refresher for the CCNA R&S.
Energy Access and Productive use of energy | PRINCE2? Foundation and Practitioner
6 年I think these questions are too theoretical and anyone who has read for the ccna cert would memorize and pass them. Instead of asking what a VLAN is, I'd instead describe a scenario where a vlan is required and expect the candidate to tell me this in there answer. Try to keep the questions practical to a real network