Networking

If you’ve got a home lab to play around in, it’s great to have remote access so that you can try things out from the road. This might mean purchasing an expensive firewall or VPN appliance but openvpn has a nice 2 user appliance that can be downloaded as an OVF file, right into your vSphere environment. Installation I mentioned that this is an OVF file, so you know the installation is going to be a snap. Download the bits from OpenVPN.net and deploy into your vSphere cluster. I’m not going to go through the entire OVF deployment, I think you’ll find it very simple even if you haven’t done it before. ...

This is a series of posts designed to help readers understand how the Internet works. This specific post looks directly at how devices know what machines are on their network segment. In previous posts, we looked at how machines communicate on the same network by utilizing frames, and how machines on different network segments use packets. The next logical question is, “How do machines know if these machines are on the same network or not?” The answer to this question is subnetting. ...

This is a series of posts designed to help readers understand how the Internet works. This specific post looks directly at collision domains. Ethernet uses a process called “Carrier Sense Multiple Access with Collision Detection” or CSMA/CD for short. This is a very long way of explaining the process of how network adapters can share the same media to communicate. Think about it if you have 10 machines on a network that are all sharing the same wires or devices, how can any of the devices understand anything with all those frames? ...

This is a series of posts designed to help readers understand how the Internet works. This specific post looks directly at how machines on different network segments communicate. In my previous post, we looked at how two machines on the same network segment exchange information by using frames. So what happens when two machines on different segments need to communicate? Encapsulation Before we get too involved in the discussion, we should take a peak at what an IP packet looks like. IP Packets relate to Ethernet frames much like one nesting doll relates to the rest in the set. ...

This is a series of posts designed to help readers understand how the Internet works. This specific post looks directly at how machines on the same network segment communicate with each other. We’ll look at the concept of a network segment in a future post, but for now all you need to think about is how two computers communicate on a Local Area Network. MAC Addresses Before we discuss how machines on the same LAN segment communicate, we need to understand what Media Access Control (MAC) addresses are. A MAC address is the physical address of a network adapter. These are 48 bit addresses that are expressed as 12 digit hexadecimal notation and are unique to each network adapter. Each manufacturer has an assigned range that they are to use for their first 24 bits, this is known as the Organizationally Unique Identifier (OUI). The second 24 bits are known as the Network Interface Controller (NIC) specific and must be unique within that vendor’s range. Keeping these ID’s unique is imperative for successful LAN communication. ...

This post was a direct result of a request from one of my readers. I hope that this post will explain VMware networks a bit more and how they fit into a production network. To begin I’d like to review how a VMware ESXi server might have its virtual switches and port groups setup to connect to a physical switch. Here is a list of networks that we’ll be working with. ...

I want to address a concern that many HP Virtual Connect customers have had about monitoring their Blade Chassis. A question I’ve received was “How do I know if I have sufficient uplinks for my traffic?” Depending on the size of the organization and their familiarity with their networking equipment, they could be monitoring the available metrics on their switches. If they are not necessarily that network savvy or don’t have the proper monitoring tools in place, they can use the throughput statistics tools within Virtual Connect. These tools only give a simplistic view to the amount of traffic that is going across your uplinks, and doesn’t show the traffic going out each blade but it does get you some great high level information. ...

If you find yourself in an unfamiliar network and want to understand how the networks are connected, it would certainly be nice to be able to tell what is connected to each other. Luckily there are a couple of protocols that are responsible for just that. Cisco Discovery Protocol (CDP) As you can probably guess from the name, the Cisco Discovery Protocol is a proprietary protocol from Cisco Systems. ...

Until recently, I never paid too much attention to flow control. I knew that it was used in networking, and that it was a setting that sometimes needed modified when I would puttyhyperterminal into a device, but that pretty much ended my knowledge of the matter. As the name suggests, “Flow Control” will limit the amount of data across a network interface. It’s a pretty simple concept but typically we’re not trying to slow down our network, but rather speed it up. Flow control can be used to slow traffic down rather than dropping frames. ...

I’ve recently had to label more network cables than I care to discuss, but found my mind wondering over the best method to label these cables. I’ve come up with three different ways to label networking cables and wanted to get some thoughts from other Engineers about how they go about this. Method 1: Same label on both sides This method creates 2 labels that are identical and puts one label on each side of the cable. This give the advantage that if you’re running multiple batches of cables all at once, you can determine exactly which cable you’re working with. ...