Category Archives: Systems

Systems

How to Sub-Delegate Reverse DNS Records Part 1

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The Purpose of DNS Sub-Delegation

Let’s say you have acquired a static IP range from your ISP. Now that you have that range, you decide you also want to control the PTR records for these addresses as well. But, PTR records typically belong to the ISP. However, you do not want to depend on the ISP for each change you’d like to make; you want more control. How can your gain more control over those PTR records?

The way to gain this control is through DNS Sub-Delegation. DNS Sub-Delegation is when your ISP forwards PTR requests to your name server so that you can have control over your record updates. In other words, the ISP delegates their authority over their PTR records to your DNS server.

Prerequisites

If you understood the implications of that last sentence, you’ll realize that you will need your own local DNS service that controls your domain. After all, if you don’t control your own domain, how are you going to control the PTR records once they are delegated to you? In this post, we’ll assume that you will manage your PTR records with your own DNS server. Continue reading How to Sub-Delegate Reverse DNS Records Part 1 →

Systems

How to Setup a TFTP Server Under CentOS/RHEL 6

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Why bother with tftp?

Many network devices such as Cisco routers and switches use tftp in order to download their IOS config updates. tftp can also be used for network based installs or for booting up diskless systems. Knowing how to setup a tftp server comes in quite handy when circumstances like these arise.

Getting started . . .

The Network Topology

Let’s say we’re dealing with a private network– 192.168.100.0/24. We’ll designate our tftp server and tftp test client as 192.168.100.5 and 192.168.100.105 respectively. You will need superuser privileges on both your server and client in order to successfully perform all of these commands.

Get the Necessary Packages

Log on to 192.168.100.5 and download the necessary programs; make sure they survive reboots:


# yum install tftp-server xinetd
# chkconfig tftp on Continue reading How to Setup a TFTP Server Under CentOS/RHEL 6 →
Systems, Uncategorized

ipfilter and ipv6

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For people running older versions of Solaris, like 8/9, the firewall of choice to install was ipfilter. Now, with Solaris 10 it has become the default, built-in with the OS. I wanted to do a short post about adding configuration settings for ipv6 and plan to cover ipv4 in detail in a later post.

One thing to note is that ipfilter must run it’s ipv6 rules under a separate file. In Solaris 10, the default location for the filter rules is in /etc/ipf and the firewall rules are located in the files ipf.conf and ipf6.conf for ipv4 and ipv6 respectfully. Here is a sample of the current file on one of my servers,


#
# ipf6.conf
#
# IPv6 Filter rules to be loaded during startup
#
# See ipf(4) manpage for more information on
# IP Filter rules syntax. Continue reading ipfilter and ipv6 →