jim – Page 5 – TECHJOCKEY.net

Linux — IPTABLES Network Firewall

Most firewalls in the consumer world are ones that are either bought at Bestbuy or supplied by your ISP as an all-in-one type of network device. These devices, such as the Linksys WRT54GL, are good enough for most user’s home setups. Providing Wireless and Wired network access with built in Firewall security. Blocking most inbound network threats , and other unwanted requests that are not pre-established (i.e. return path from an outbound request). Some of these consumer routers can be even further enhance with a rich set of plugins and network tools by using custom firmwares. DD-WRT, Tomato, or openWRT are all interdependent communities, who develop custom firmware to be used with these consumer all-in-one routers. You can check your devices compatibility with their firmware at each of their websites.

I for one own a Linksys WRT54GL router and have used both DD-WRT and Tomato. Both of these custom firmwares as well as the stock firware(Linksys) provide enough security, accessibly, and capacity for a typical consumer. However, that’s not what this article is about! This article is how to setup your own Network Firewall using a standalone Linux box! Woot!.

Why build a standalone Network Firewall?

March 20, 2013 by jim Linux Security 6

Inter-VLAN routing with Linux & PowerConnect 5324

I recently purchased a 24-port Gigabit Layer 2 Switch that supports VLAN tagging and trunking. Dell PowerConnect 5324, see here, has 24 Ethernet ports and is capable of tagging and untagging Frames at wire speed. It is a discontinued model, however doing some googling I found a updated firmware and IOS image!

Physical Topology

The topology is pretty typical of “routing-on-a-stick” for Multiple VLANs. I have a Linux server running Ubuntu 12.04 with a single NIC and the Dell PowerConnect switch.

Port configuration:
Network 1 = g1 – g16
Network 2 = g17 -g23

802.1q Information:
Switch Trunk Port = g24
Router Trunk Port = eth1

Logical Topology

I have a single LAN I want logically separated using a single switch. The VLAN IDs are 100 & 200. The VLAN subnets and ports will be as follows;

Subnets:
VLAN 100 = 192.168.1.1/24
VLAN 200 = 192.168.2.1/24

VLAN Access Ports:
VLAN 100 = g1 – g16
VLAN 200 = g17 -g23

March 11, 2013 by jim Linux Network 4

OpenVPN — Creating a Client VPN Setup

Before we begin I want to clearly identify the scope of this tutorial. There are different types of VPN, we will be creating a Client VPN which implies a many to one relationship. We will have multiple clients connecting via VPN to a single OpenVPN server. This OpenVPN server will assign IP addresses to each successfully authenticated client. Using this IP Address, client’s may, depending on your network security, access devices on a private network. Effectively appearing as if the Client was directly tied into the Private Network. If you are looking for a site-to-site VPN tunnel via IPSEC this is out of the scope of this tutorial.

Our Simple Client VPN Topology

February 20, 2013 by jim Linux Network 0

Linux — iSCSI Target using open-iscsi

I recently set up an iSCSI SAN for use with VMWare Server. The set up was basically a Linux Ubuntu Server target with 2 network links to a single VNWare Server as the integrator. I also included iSCSI multi-pathing by enabling it on the initiator (VMWare Server).

This is how I set up an Linux SAN Target with iSCSI, interfacing with VMWare 5.1. as the iSCSI Initiator.

Continue reading…

January 13, 2013 by jim Linux SAN 4

F5 BIGIP — Determine the Healthcheck Source Address

I was discussing some F5 LTM Healthcheck Monitor capabilities with a colleague of mine at work the other day, when he brought up a great question.

What does an F5 LTM use for a source IP address when connecting to pool members for the healthcheck monitor service? Especially on a Multi-Network setup.

To answer this question we have to consider the typical LTM cluster set up . Usually set up in pairs of two(2), one acting as an Active unit and the other as Standby unit. Each unit has it’s own Self IP for each “network leg” it is attached to. The Active and Standby unit also share a “Floating IP address”, which is used for the backend traffic to pool members. But back to the question, let’s use the following example:

January 11, 2013 by jim F5 Network 4

Squid Proxy — EasyList to SquidGuard Expression List Conversion

Hi all! It’s seems to be difficult to keep up with the EasyList expression lists, and to make matters more confusing, the conversion from one EasyList expression list to SquidGuard can be cumbersome. There are a few article out on Google that people have posted their own SED files to convert from EasyList to squidGuard, that will manipulate the EasyList expression list and convert it to be compatible with SquidGuard. However, most are outout of date and will cause squidGuard to fail to initialize the expression list when issuing a

>squidGuard -C all

November 16, 2012 by jim Linux Security 13

Linux — Apache Logs -Stop Logging Certain URIs

I recently posted an article talking about HAProxy as a load balancer. In the article I spoke about using a HTML health check file to maintain status of each servers Apache instance. The problem is this will flood your Apache server access logs every time this health check occurs, which I believe is every 2 seconds.

So you end up with a log file like this:

To correct this issue we need to modify the apache2.conf file on each server, and explicitly tell Apache NOT to log this URI to the access logs. So, from the previous article the culprit URI is /healthcheck.html. Open your Apache configuration file.

sudo vi /etc/apache2/apache2.conf

Now add this above the CustomLog section:

#logs 
SetEnvIf Request_URI "^/healthcheck.html$" dontlog 
CustomLog /www/logs/mysite_access_logs combined env=!dontlog 
ErrorLog /www/logs/mysite_error_logs

NOTICE: Make sure you have the ” escape character for any special characters.

That’s it! No more spamming of all the health checks to our Apache logs!!

Sources:

http://httpd.apache.org/docs/1.3/logs.html#conditional

November 13, 2012 by jim Linux 0

HAProxy — HTTP Load Balancing HAProxy1.4

I’ve posted a few articles on load balancing with the use of BIGIP F5 hardware appliances. However, there are also a few alternatives available, some even free! HAProxy is a popular load balancing application that has a robust collection of features.

HAProxy is “The Reliable, High Performance TCP/HTTP Load Balancer”, taken right from the title of their web page. It has many different uses available, for this article I am going to focus on the HTTP load balancing functionality of it. Our scenario is as follows:

November 10, 2012 by jim Linux Network 3

Linux — nTop and darkstat Traffic Monitoring

Hey All, so I posted an article on setting up your own Linux based firewall using iptables, and thought it would be nice to be able to monitor the connections coming in and out of each interface on the Linux Firewall. So I installed and played with two passive Network Traffic Monitoring applications; nTop and darkstat.
Continue reading…

October 26, 2012 by jim Linux 2

Linux — Recovering from Drive Failure with mdadm

So it happened. I had a drive fail on me. Degrading my RAID 6 media server. Luckily I was notified by mdadm and was able to order a new one from newegg.com and rebuild it.

I want to walk through the steps I took getting my RAID file system backup and running, starting with the notification I received to my gmail account (which i received on my phone).

October 19, 2012 by jim Linux SAN 0