Interview Questions for CCNA Candidates with Answers- Basics II


After out Part-I, we are again with Part-II

CCNA Interview Questions

What command copies router configuration from NVRAM to a file server? 
copy startup-config tftp

What command assigns and enables IPX on an interface? 
ipx network 4a

How does TCP provide flow control and error checking? 
Acknowledgements and windowing.

Using Cisco IOS, what PPP data compression methods can be used?  
Stacker and Predictor.

What command can verify Application layer connectivity? 
Telnet.

What command switches from User to Privileged mode? 
enable

What command will deny all telnet traffic from subnet 2.1.3.0? 
deny all telnet traffic from 2.1.3.0

Which of the following exist at the Transport Layer?
LLC
IP
SQL
UDP*
ARP

What command line keyword matches Ethernet_SNAP? 
snap

Among the five classes of TCP/IP addresses, how many are available to the public? 
3.

After entering the command ‘router igrp 50,’ what command enables IGRP on the router for interace E1, with an address of 155.88.3.5 and a mask of 255.255.255.0? 
network 157.89.0.0

In what OSI layer do EBCDIC and ASCII exist? 
Presentation.

What command Continue reading

Are VXLAN-Based Large Layer-2 Domains Safer?

One of my readers was wondering about the stability and scalability of large layer-2 domains implemented with VXLAN. He wrote:

If common BUM traffic (e.g. ARP) is being handled/localized by the network (e.g. NSX or ACI), and if we are managing what traffic hosts can send with micro-segmentation style filtering blocking broadcast/multicast, are large layer-2 domains still a recipe for disaster?

There are three major (fundamental) problems with large L2 domains:

Read more ...

A short Story on vPC- Virtual Port Channel in Cisco Datacenter Environment

Today I am going to talk about vPC and vPC+. These two technologies are used in the datacenter environment over the Cisco Nexus Switches where you bundled the links.

vPC stands for Virtual Port Channel and is a virtualized technology, So it allows links that are physically connected to two different Cisco Nexus 7000 Series devices to appear as a single port channel to a third device. The third device can be a switch, server, or any other networking device that supports link aggregation technology. 

There are lot of benefits of vPC which can allow to work better in your datacenter environment

  • It actually eliminates Spanning Tree Protocol blocked ports
  • with the help of vPC, you can use all the uplink available bandwidths
  • Allows dual homed servers to operate in active-active mode
  • Providing Fast convergence on link failures
  • Providing dual active default gateways for servers
  • Simplify your network design and build high resilient and robust Layer 2 Network.
  • Excellent Scalability and seamless virtual machine mobility.
So now I will talk about the various components used in the vPC environment. I hope datacenter guys already heard and know about these components. I will just put the component and the meaning of Continue reading

Cisco Router as Terminal Server- Why and how to configure

Today I am going to talk about the Cisco Router as a Terminal server in the datacenter environment. So the question is why and where we are going to use the terminal server?

Let's talk about the Terminal server what exactly is and why we are using the Terminal server in the datacenter environment.

Terminal Server:
A terminal server commonly provides out-of-band access for multiple devices. A terminal server is a router with multiple, low speed, asynchronous ports that are connected to other serial devices, for example, modems or console ports on routers or switches.

Fig 1.1- Cisco Router as Terminal Server

A terminal server works via a reverse telnet operation. Next, connect the asynchronous octal cable(s) to the 2511's 68-pin SCSI interface(s). Then connect a rolled console cable from the COM1 port (serial) on your PC to the console port on the terminal server. Power the device on and use a terminal emulator such as HyperTerm to connect.

The terminal server allows you to use a single point to access the console ports of many devices. A terminal server eliminates the need to configure backup scenarios like modems on auxiliary ports for every device. You can also configure Continue reading

Flow Trend

The open source sflow-rt/flow-trend project displays a real-time trend chart of network traffic that updates every second. Defining Flows describes how to break out traffic by different traffic attributes, including: addresses, ports, VLANs, protocols, countries, DNS names, etc. 
docker run -p 6343:6343/udp -p 8008:8008 sflow/flow-trend
The simplest way to run the software is using the docker. Configure network devices to send standard sFlow telemetry to Flow Trend. Access the web user interface on port 8008.

Liveblog: Cloud Native Infrastructure

This is a liveblog of the HashiConf 2017 session titled “Cloud Native Infrastructure.” The speaker is Kris Nova, a Senior Developer Advocate at Microsoft. Kris, along with Justin Garrison, authored the O’Reilly Cloud Native Infrastructure book (more information here). As one of the last sessions (if not the last session) I’ll be able to attend, I’m looking forward to this session.

Kris is a self-confessed Linux lover, loves writing in Golang, is a Kubernetes maintainer, and works on Azure at Microsoft.

So, what is “cloud-native infrastructure”? To answer that, Nova first tries to answer “what is a cloud?” Nova breezes by that definition without going into any real detail (or any real definition), and proceeds to talk about what infrastructure is. Again, Nova breezes by that without providing any real definition or depth, and proceeds to ask “Why is infrastructure better in the cloud?” According to Nova, infrastructure is better in the cloud because management can be as simple as an HTTP request. The next few slides in Nova’s presentation compare the “traditional” ways of managing infrastructure (provisioning switches, patching cables, troubleshooting problems) are now, when infrastructure is in the cloud, as simple as a series Continue reading

HashiConf 2017 Wrap Up

HashiConf 2017 is a wrap for me, and as I’m sitting here at the airport lounge in Austin I’d thought I’d post links back to the liveblogs I published as well as a few thoughts on the conference overall.

Liveblogs

First, here are links to the liveblogs published during the event:

Closing Thoughts

I think it was a pretty good event. The venue (JW Marriott in Austin) seemed roughly appropriate for the number of attendees (around 800, I believe), although some additional seating during meal times would have been a good idea. The conference Wi-Fi was mostly OK, though it had its moments.

The quality of sessions varied; some sessions were very good; others, not so much (unfortunately). It would have been good to see a clearer breakdown of the sessions according to area/theme. They had 3 content tracks, but it wasn’t really clear to me if the tracks had any central theme. I, personally, bounced around all three tracks.

I did like the inclusion of high-top tables at the Continue reading

China Arms Upgraded Tianhe-2A Hybrid Supercomputer

As an economic powerhouse and with a rising military and political presence around the world, you would expect, given the inherent political nature of supercomputing, that China would have multiple and massive supercomputing centers as well as a desire to spread its risk and demonstrate its technical breadth by investing in many different kinds of capability class supercomputers.

And this is precisely what China is doing, including creating its own offload accelerator, based on digital signal processors. This Matrix2000 DSP accelerator, which was unveiled at the ISC16 supercomputing event last year and which is being created by the National University …

China Arms Upgraded Tianhe-2A Hybrid Supercomputer was written by Timothy Prickett Morgan at The Next Platform.

Worth Reading: Docbook

Computers were first invented to do math, and they do it really well. But it didn’t take long for users to repurpose their futuristic calculators into fancy, dynamic typewriters. Now human-readable text drives computing, so it’s important to choose the right format for the text you write. DocBook is an XML schema. XML is an extensible markup language a lot like HTML. It’s truly ubiquitous, but you may know it by RSS or Atom, the Open Document formats of LibreOffice and Apache OpenOffice, Inkscape and the SVG file format, and much more. In fact, it’s safe to say that if you own a computer or mobile device, there’s XML on it. —Seth Kenlon @ Opensource

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Data and power could run over the same wireless network

Combining power to operate equipment, as well as delivering substantial data rates that are good enough for video — in the same piece of radio kit — is now obtainable, scientists say.The developing system works similar to how charging pads provide power to a toothbrush or a mobile phone without having to be connected through wires. However, in this case, the apparatus doesn’t need any physical contact with the device and data can be sent at the same time.Magnetic fields are being used to transmit power through the air, North Carolina State University researchers say in a press release.To read this article in full or to leave a comment, please click here

Data and power could run over the same wireless network

Combining power to operate equipment, as well as delivering substantial data rates that are good enough for video — in the same piece of radio kit — is now obtainable, scientists say.The developing system works similar to how charging pads provide power to a toothbrush or a mobile phone without having to be connected through wires. However, in this case, the apparatus doesn’t need any physical contact with the device and data can be sent at the same time.Magnetic fields are being used to transmit power through the air, North Carolina State University researchers say in a press release.To read this article in full or to leave a comment, please click here

Reaction: Networks are not cars or cell phones

The network engineering world has long emphasized the longevity of the hardware we buy; I have sat through many vendor presentations where the salesman says “this feature set makes our product future proof! You can buy with confidence knowing this product will not need to be replaced for another ten years…” Over at the Networking Nerd, Tom has an article posted supporting this view of networking equipment, entitled Network Longevity: Think Car, not iPhone.

It seems, to me, that these concepts of longevity have the entire situation precisely backwards. These ideas of “car length longevity” and “future proof hardware” are looking at the network from the perspective of an appliance, rather than from the perspective as a set of services. Let me put this in a little bit of context by considering two specific examples.

In terms of cars, I have owned four in the last 31 years. I owned a Jeep Wrangler for 13 years, a second Jeep Wrangler for 8 years, and a third Jeep Wrangler for 9 years. I have recently switched to a Jeep Cherokee, which I’ve just about reached my first year driving.

What if I bought network equipment like I buy cars? What sort Continue reading

Worth Reading: WeChat spying revelations

It has long been known that due to WeChat keeping its servers inside China, the lack of legal protection of privacy data, and the control over companies by police, that WeChat data is not safe, and can, without protection, be accessed by police or other state actors more or less at will. This has naturally made people shy away from using WeChat for any more serious or political discussions. More and more court cases of people being prosecuted simply based on private chat messages to friends have further illustration this. At the same time, at the time of the Occupy Central movement in Hong Kong, it was shown that a ‘Trojan’ virus was being employed to surveil users remotely. —Safeguard Defenders @ China Change

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