Tag Archives: networking

How To Configure Network Teaming In Linux

Configure Network Teaming

In Linux it is possible to aggregate multiple network links together into a single logical link which can either increase network throughput or redundancy. For example we can assign an IP address to a group of two network interfaces to double our throughput, or reserve one interface for backup purposes so if the first one fails we can fail over.

Here we’re going to cover how to create and configure a network team with two different network interfaces.

Read more »

Configure IPv6 Addresses And Basic Troubleshooting In Linux

How To Configure And Troubleshoot IPv6 Addresses In Linux

In the past many system administrators have simply resorted to disabling IPv6 rather than properly configuring it, continuing to rely on the older IPv4 which has worked just fine for a very long time. As the IPv4 address space has since become exhausted, administrators are starting to slowly take up IPv6 out of necessity.

Here we’re going to cover how to configure IPv6 addressing in Linux and provide some basic tips and advice for troubleshooting IPv6 network issues.

Read more »

Use SELinux Port Labeling To Allow Services To Use Non-Standard Ports

SELinux Ports

By default SELinux policy defines the ports that a particular service is allowed bind to and make use of with port labeling. This increases system security by preventing random services or malicious code from being able to bind to a well known defined port that may otherwise be used by a legitimate service.

In order to change a service to use a non standard port we must change SELinux policy and specify the SELinux port types that are allowed to use specific ports.

Read more »

How To Create Static Routes to Route IP Traffic

Static Route

By default all network traffic will normally be configured to route via the default gateway, that is the router attached to the network interface. It may not always be the case that you want all traffic to take the same path, in these instances we can set additional static routes that will forward specific traffic out of a different interface rather than the default gateway. This may be required if you need to be able to reach a particular network that your default gateway router does not know about.

Here we’re going to cover how to configure a static route in Linux.
Read more »

How To Enable Telnet Client in Windows Server 2016

By default the telnet client in Microsoft’s Windows operating systems is disabled, this is unfortunate as it is an extremely useful tool which can be used for testing TCP connectivity to external hosts on a specified port.

This is great when you’re trying to troubleshoot network connectivity problems, for example, say we have a web server which should be listening on port 80 to serve HTTP traffic but we are not able to load a web page, by using telnet to connect to the web server on port 80 we can verify the connectivity.

It may be that the connectivity is fine but there is a problem with the web server, or that the web server is stopped and the port is not listening at all, for instance. With telnet we can get a better understanding of what’s going on.

Read more »

Updating Solaris via Squid Proxy Server

If you have a Solaris server that does not have direct access to the Internet and cannot perform an update, what can you do? Configure a proxy server that has Internet access of course! Here is how it’s done.

In this example we will be using the popular Squid Proxy. While this can also act as a cache we are only concerned with its proxy functionality here. We will also be configuring the Solaris publisher to make use of a proxy server so that updates are downloaded through the proxy.

Read more »

How to enable the Telnet Client in Windows 10

By default the telnet client in Microsoft’s Windows operating systems is disabled, this is unfortunate as it is an extremely useful tool which can be used for testing TCP connectivity to external hosts on a specified port.

This is great when you’re trying to troubleshoot network connectivity problems, for example, say we have a web server which should be listening on port 80 to serve HTTP traffic but we are not able to load a web page, by using telnet to connect to the web server on port 80 we can verify the connectivity.

It may be that the connectivity is fine but there is a problem with the web server, or that the web server is stopped and the port is not listening at all, for instance. With telnet we can get a better understanding of what’s going on.

Read more »

How to “ping” a port

Most of us would be familiar with the simple ICMP based ‘ping’ command which allows us to test for a basic response from some network connected device. While great for basic troubleshooting it does not allow us to confirm if the particular host at the other end is responding on TCP or UDP ports where the majority of services are likely to be provided.

Ping isn’t the be all and end all of network troubleshooting, if a firewall blocks inbound ICMP traffic then a ping will not succeed which can produce a false perception that the host is down as it is not responding to the ping, however other services could still be responding fine.

Alternatively while ping may come back fine with a response it doesn’t indicate if a web server is responding on port 80 for HTTP requests, the web server may have failed and no longer be responding.

So if ping is ICMP based, can we hit a TCP or UDP port for response instead? The answer is yes, let’s take a look.

Read more »

How to test network connectivity with telnet

This post is a follow on from my post last week regarding how to install the telnet client. The telnet client is simple yet extremely powerful in helping us gain a quick idea of where a problem may lie with TCP connectivity, it’s one of my first go to tools to use when testing a network connection to a server.

Read more »

How to enable the telnet client in Windows 8.1

By default the telnet client in Microsoft’s Windows operating systems is disabled, this is unfortunate as it is an extremely useful tool which can be used for testing TCP connectivity to external hosts on a specified port.

This is great when you’re trying to troubleshoot network connectivity problems, for example, say we have a web server which should be listening on port 80 to serve HTTP traffic but we are not able to load a web page, by using telnet to connect to the web server on port 80 we can verify the connectivity.

It may be that the connectivity is fine but there is a problem with the web server, or that the web server is stopped and the port is not listening at all, for instance. With telnet we can get a better understanding of what’s going on.

Read more »