Basics of Multicast Addresses ( 224.0.0.0 to 239.255.255.255)

Today I am going to talk about basics of Multicast from the beginning. Before starting the concept of multicast you need to know about the unicast and the broadcast type of networks.

Unicast: Unicast is the traffic from from the single user to the single destination.
Broadcast: Broadcast is the traffic flow from the single user to everyone in the network.
Multicast: Multicast is the traffic flow from the single user to the specific group of the destinations in the network.

Fig 1.1- Multicast Vs Unicast

IP Multicast
IP multicast works as follows :
  • Multicast groups are identified by IP addresses in the range 224.0.0.0 - 239.255.255.255 (class D address) 
  • Every host (more precisely: interface) can join and leave a multicast group dynamically : no access control 
  • Every IP datagram sent to a multicast group is transmitted to all members of the group
  • IP multicast service is unreachable
  • IP multicast only supports UDP as higher Layer which means there is no multicast TCP.
  • All D class addresses are Multicast addresses. The addresses range are shown above from 224.0.0.0 to 239.255.255.255
  • These addresses are dynamically Continue reading

DNS- Domain Name Server

Today I am going to talk about the DNS server. I knew some of the you already knew about the DNS. DNS stands for Domain Name Server and is a service to translate hostname into IP address. DNS is a distributed database implemented in a hierarchy of name servers and DNS is an application level protocol for message exchange between clients and servers.

Now question is Why we required DNS service ?
  • It is easier to remember a host name than it is to remember an IP address. 
  • A name has more meaning to a user than a 4 byte number. 
  • Applications such as FTP, HTTP, email, etc., all require the user to input a destination 
  • The user generally enters a host name 
  • The application takes the host name supplied by the user and forwards it to DNS for translation to an IP address 
Fig 1.1- DNS 

How DNS- Domain Name Server Works ?

  • DNS works by exchanging messages between client and server machines. 
  • A client application will pass the destination host name to the DNS process (in Unix referred to as the get host by name() routine to get the IP address. 
  • The application then sits Continue reading

DHCP Message Types

Today I am going to talk about the DHCP message types and the meaning of all the requests sent by server and client in DHCP process. The messages are shown below

Messages Types
  • DHCPDISCOVER 
  • DHCPOFFER 
  • DHCPREQUEST 
  • DHCPDECLINE 
  • DHCPACK 
  • DHCPNAK 
  • DHCPRELEASE 
  • DHCPINFORM 
Fig 1.1- Sample DHCP request
Fig1.2 - Sample DHCP Response


DHCPDISCOVER: Broadcast by a client to find available DHCP servers. 

DHCPOFFER: Response from a server to a DHCPDISCOVER and offering IP address and other parameters. 

DHCPREQUEST: Message from a client to servers that does one of the following: 
  • Requests the parameters offered by one of the servers and declines all other offers. 
  • Verifies a previously allocated address after a system or network change (a reboot for example). 
  • Requests the extension of a lease on a particular address. 
DHCPACK: Acknowledgement from server to client with parameters, including IP address. 

DHCPNACK: Negative acknowledgement from server to client, indicating that the client's lease has expired or that a requested IP address is incorrect. 

DHCPDECLINE: Message from client to server indicating that the offered address is already in use. 

DHCPRELEASE: Message from client to server canceling Continue reading

IP CLOS – EBGP – Multipath Multiple-as

Hi,

We have seen how iBGP was used to do the IP Clos with a RR Setup, how about eBGP.

Configurations / EVE Topology – https://github.com/r2079/JDC

Two simple rules

  • All spines have connections to all leaves – eBGP
  • No leaf or No spine devices have interconnected BGP.

Here is the topology.

 

 

The picture says 1000 words here – How the physical links are connected that’s how the bgp flows.

 

Lets see the BGP Status on R1 and R2

 

Since the hurdles of multipath has been explained. The use ADD-Path is not required here, instead since the update comes from Different AS numbers (R4 and R5) giving out the same update, we have to use another knob called MULTIPLEAS. This has to be on all Spine and leaf devices so that proper Load Balancing can be done along with EXPORTLB policy in the forwarding table.

Lets see one of the routers

 

Verification from R6

 

Regards

Rakesh

 

8 Use Cases for Modernizing and Automating Workflows

Use Cases for Modernizing and Automating

Managing an organization’s many tools and business processes is becoming increasingly complicated as technology expands. Whether your teams are performing their weekly system reboot, or looking to configure instances to a desired state, it’s no secret that automation is critical to increase speed, efficiency, productivity, and accuracy. Listed below are several instances1 where automation can help across your enterprise.


  • Weekly system reboot: There’s nothing worse than doing the same thing for 8 hours a day! Eliminate repetitive, manual processes with automation.
  • Enforce security guidelines: Rules are rules. It’s best to automate in an effort to achieve strict security standards.
  • Monitor configuration drift: Use check mode with Ansible tasks to enforce desired settings and see if your configuration has drifted.
  • Disaster recovery: Disaster recovery can involve a wide range of components. Act across different variables of the technology stack to identify problems and eliminate cross team dependencies.
  • Command blaster: Remarkably easy to write, you can run commands across your environment for any number of servers.
  • Database binary patching: Several databases use outdated binary sets. Patch the binaries in accordance with the release of the latest patch.
  • Instance provisioning: Use modules for several cloud providers to create new instances and tailor Continue reading

Network Automation Engineer Persona: Part One

This is the first post of a series on the persona between “network engineer” and “developer”. This role does not exist in myth, but it is a natural evolutionary step forwards. This position inherits skills from both ends of the scale, but in itself is an emerging role in organisations globally.

Why describe personas? They are important because:

1. They provide a roadmap for a career
2. They provide a set of skill requirements to master for a role matching the persona
3. They provide a set of tool consumption and usage hints
4. They provide a viewing glass to defining thought processes

Some of the challenges both vendors and network technology consumers are facing today are related to the set of evolving personas in our field, therefore it’s crucial to understand them properly. Remember when you wanted to be a network engineer? You became the persona and worked your way through a set of learnings. Your thoughts and habits changed, along with your recognition and self awareness.

Evolution of Roles

Every industry evolves and some industries disappear. The need to move packets about on the Internet hasn’t evolved out of existence just yet; our current highly generalized reality is: Continue reading

Examining network connections on Linux systems

There are a lot of commands available on Linux for looking at network settings and connections. In today's post, we're going to run through some very handy commands and see how they work.One very useful command is the ifquery command. This command should give you a quick list of network interfaces. However, you might only see something like this -- showing only the loopback interface: $ ifquery --list lo If this is the case, your /etc/network/interfaces file doesn't include information on network interfaces except for the loopback interface. You can add lines like the last two in the example below -- assuming DHCP is used to assign addresses -- if you'd like it to be more useful.To read this article in full or to leave a comment, please click here

IT spending increases for software-defined storage, on-demand services

Two new spending reports paint a rosy picture for some IT vendors, but it isn’t looking so great for the traditional players.At Gartner’s Symposium & ITxpo last week, the firm released a report stating the global IT market is expected to reach $3.7 trillion next year, a 4.3 percent increase over the $3.5 billion expected for this year.Spending on traditional data center hardware and systems is expected to stay flat, continuing a trend we’ve seen for a while now as businesses ramp up spending on three on-demand services: infrastructure as a service (IaaS), platform as a service (PaaS), and communication as a service (CaaS).Also on Network World: Report confirms on-premises data center spending declined "The IT buying landscape is changing: Digital business transformation is an effort to create connected, platforms and new industry revenue streams," analyst John-David Lovelock wrote in the report. "Organizations that are not creating new digital business models or new ways to engage constituents or customers are falling behind. Those vendors that do not move more quickly than their clients will be left behind." To read this article in full or to leave a comment, please click here

IT spending increases for software-defined storage, on-demand services

Two new spending reports paint a rosy picture for some IT vendors, but it isn’t looking so great for the traditional players.At Gartner’s Symposium & ITxpo last week, the firm released a report stating the global IT market is expected to reach $3.7 trillion next year, a 4.3 percent increase over the $3.5 billion expected for this year.Spending on traditional data center hardware and systems is expected to stay flat, continuing a trend we’ve seen for a while now as businesses ramp up spending on three on-demand services: infrastructure as a service (IaaS), platform as a service (PaaS), and communication as a service (CaaS).Also on Network World: Report confirms on-premises data center spending declined "The IT buying landscape is changing: Digital business transformation is an effort to create connected, platforms and new industry revenue streams," analyst John-David Lovelock wrote in the report. "Organizations that are not creating new digital business models or new ways to engage constituents or customers are falling behind. Those vendors that do not move more quickly than their clients will be left behind." To read this article in full or to leave a comment, please click here

A Community Network in the Remote Georgian Region of Tusheti

About a year ago, Internet Society partnered with its Georgian Chapter, Small and Medium Telecom Operators Association of Georgia, Freenet LTD Association, Internet Development Initiative and Tusheti Development Fund to help the remote and mountainous region of Tusheti to build access to the Internet. The network was recently completed as a true community effort and became fully operational in August.

Impact

When the Internet Society team visited the village of Omalo in Tusheti two weeks ago for an official launch ceremony, the Internet speeds measured at 4-5 Mbps. A dramatic change to a region, where many villages are not even covered by mobile signal!

During our brief stay in Omalo the impact of the newly established Internet connection was not evident at first glance. Apart from a couple of visible repeaters on the surrounding mountains, people were getting on with their usual daily chores while a group of tourists travelled past on horseback. The local community, however, was exuding a sense of achievement and optimism. The recently established Internet access opens new opportunities for tourism and cultural preservation, and provides an essential communication channel for healthcare and potential emergency situations.

Partnership

The engine behind this effort was a solid Continue reading

Microburst: Update on the HTML Home Network Diagram

Moving Packets - Microburst

 

Last week I published an article called Making a Clickable HTML Network Diagram using OmniGraffle. One of the questions I was asked was whether I’d tried doing the same in draw.io or Gliffy. I have not, although I do use Gliffy a fair amount, and I have dabbled with draw.io.

Thankfully, Keith Miller (@packetologist) is on hand to provide the answer! Keith has put together an article mirroring a similar process using the free (and platform-agnostic) draw.io. Definitely worth a read, and a great example of a free tool making our lives way easier.

Link: CLICKABLE HTML NETWORK DIAGRAMS WITH DRAW.IO

Thanks, Keith for the excellent demonstration!

If you liked this post, please do click through to the source at Microburst: Update on the HTML Home Network Diagram and give me a share/like. Thank you!

Adminstravia 20171009

Where’s Russ?

This is my second week of PhD seminars this fall—the only time in this program I intend to take two seminars back to back. One of the two was, in fact, very deep philosophy, so I was pretty taxed trying to pull the material together.

At the same time, the book has passed through technical review, and is now in author review. I hope it soon be in proofs. The combination of these two things, the book and the PhD work, along with multiple other things, is what caused me to call a pause in blogging for these two weeks. The date to watch is the 29th of December. It might be released earlier, but it is hard to tell right now. I will do a post a little later this week describing the book for those who are interested.

Tonight (Monday) I will be recording a new Network Collective show on the Intermediate System to Intermediate System (IS-IS) protocol, and we have a long list of History of Networking guests to bring on. The history material has turned out to be absolutely fascinating; I am thankful we have the connections available, and the recording venue, and someone Continue reading

What will programming look like in the future?

 

Maybe programming will look something like the above video. Humans and AIs working together to produce software better than either can separately.

The computer as a creative agent, working in tandem with a human partner, to produce software, in a beautiful act of co-creation.

The alternative vision—The Coming Software Apocalypse—is a dead end. Better requirements and better tools have already been tried and found wanting. Requirements are a trap. They don't work. Requirements are no less complex and undiscoverable than code. Tools are another trap. Tools are just code that encode an inflexible solution to a problem that's already been solved.

Admittedly, I'm cheating. I have no idea how any of this will work, but here are the seeds of how it has already started:

Here's what we do know: neither tools or requirements are a silver bullet, they are a method of incrementally improving software quality. Software production quantity is not increased at all.

What we need is a manufacturing process that puts software production on an exponential curve. The only conceivable tool we have at Continue reading

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