All posts by nlogician

Fiber Factoids, Part 1 – A primer on common fiber optic cable types

If you’ve been in the IT industry for any amount of time you are likely to have ran across fiber optic patch cables in use in various different installations. Typically, you will most often see fiber optic cables used for an uplink to an internet service provider, in between network devices between buildings in a campus network, or in a datacenter where large amounts of bandwidth and high speeds are required.

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What is a null route and why do I need one?

Definition

There are several names for a null route, such as a “bit bucket”, a “black hole”, or just a null0 route. They all refer to the same basic mechanism that points traffic to a virtual interface on a router. That in turn is used for managing unwanted traffic to prevent loops or entering routes into the RIB (routing information base) of a router.

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FIREPOWER DNS Sinkhole

Many admins inadvertently design a sinkhole by null routing unused ranges within their core in order to limit unnecessary traffic. Some may even advertise these ranges from a Linux server running zebra or quagga for advanced alerting while monitoring for the propagation of worms or enumeration scans. In this post, we will discuss a similar idea for DNS using Firepower.

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Basic DHCP Setup

Introduction

When it comes to efficiently assigning IP addresses to multiple clients, DHCP is the de facto standard in most networks. In this post, we’ll explore DHCP configuration on Red Hat Enterprise Linux 7 and give an example of how to install it, as well as a few configuration options for dhcpd. With a basic understanding of DHCP, you can get your network up and running almost immediately.

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Unboxing and initial setup of a Meraki MX Security Appliance

Meraki is a pretty well known company, and has been a part of Cisco since 2012. There are a multitude of cloud based managed Wi-Fi solutions, but Meraki is one of the most prolific and has a variety of cloud managed products to suit most any size company’s needs. Several of their devices have similar setup steps, but today we will cover the initial out of the box setup of a Meraki MX64 security appliance that will have your MX appliance online and configured in your dashboard in no time.

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Add a Swap File to RHEL/CentOS

Sometimes, due to some new specific server requirements, you will find it necessary to increase your swap space. Even if your swap partition is setup as a Logical Volume, your requirements may exceed what is available. This is where creating a new swap file is the best option. In this example, we are going to add a new 12GB swap file.

Check Current Swap Space

Verify the total amount of used and free physical and swap memory with the free command and the -h human-readable flag

# free -ht
              total        used        free      shared  buff/cache   available
Mem:           755G        321G        3.0G         62G        430G        670G
Swap:            4G          1G          3G
Total:         771G        322G          6G

Display the swap usage summary by device using swapon. Same as cat /proc/swaps

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