Tag: dhcp

Linux

DNS and multiple VPNs: Using dnsmasq to access multiple dns suffixes

On my Fedora 15 laptop, I'm almost always connected to several VPNs simultaneously. One VPN to my office or to my home (depending on where I am), one to the data center, one to a customer. These connections all have their own DNS server with their own suffix.

To make all dns suffixes working, I created a script that redirects all outgoing DNS traffic to dnsmasq running on localhost, which in turn forwards all requests for .lan to 192.168.15.254 and all requests for .gl to 192.168.1.254.

The script was put in /etc/NetworkManager/dispatcher.d/10-DNS:

if [ -e /var/run/dnsmasq.localhost ]; then
        cat /proc/`cat /var/run/dnsmasq.localhost`/cmdline |grep dnsmasq >/dev/null 2>/dev/null && \
        kill `cat /var/run/dnsmasq.localhost`
fi
 
if [ "$2" == "up" ]; then
        cp /etc/resolv.conf /etc/resolv.conf.dhcp
        echo nameserver 127.0.0.1 >  /etc/resolv.conf
        echo domain $DHCP4_DOMAIN_NAME >> /etc/resolv.conf 
        echo search $DHCP4_DOMAIN_NAME >> /etc/resolv.conf 
        /usr/sbin/dnsmasq -C /dev/null -r /etc/resolv.conf.dhcp --server=/gl/192.168.1.254 \
            --server=/lan/192.168.15.254 --bind-interfaces --listen-address 127.0.0.1 \ 
            --pid-file=/var/run/dnsmasq.localhost
fi

Once I had to fix resolv.conf manually when I connected my laptop to my Samsung Galaxy SII as well. This may mean I need to improve the script some day, but for the time being, it works good enough.

© GeekLabInfo DNS and multiple VPNs: Using dnsmasq to access multiple dns suffixes is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

PXEboot with CentOS 5.6 and dnsmasq

Install the required software:
yum install dnsmasq

Open up the firewall:
/sbin/iptables -I INPUT -m udp -p udp --dport 67 -j ACCEPT
/sbin/iptables -I INPUT -m udp -p udp --dport 53 -j ACCEPT

Then run:
dnsmasq -d --interface=br0 --dhcp-range=181.30.68.111,static --dhcp-host=84:2b:2b:78:30:79,181.30.68.112 --dhcp-option=option:router,181.30.68.65 --dhcp-boot=pxelinux.0 --enable-tftp --tftp-root=/var/ftpd

Put all required files, such as pxelinux.0 from the package syslinux in /var/ftpd

Ubuntu/Debian

I'm running RedHat-based software on all of my machines. Above information may be useful for Ubuntu/Debian users, but it's not tested and I'm not supporting it.

Servers: RedHat Enterprise Linux/CentOS is more suitable for servers, as there's a lot of professional level support available. I think that's important, because if I say, get a car accident, I want the servers to be managable by another professional.

Desktops/Laptops: RPM packages are pretty exchangable between RedHat-based platforms. That's a good reason to run Fedora on the desktop.
© GeekLabInfo PXEboot with CentOS 5.6 and dnsmasq is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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Linux

PXE Boot with old-style dhcp and tftp

In this article I'm covering the use of old-style dhcp and tftp, which is useful for company networks that have/need a complete dhcp server running. Personally, for smaller setups, I now prefer dnsmasq to do the job.

Booting from PXE

With most modern onboard and PCI network interface cards (NICs), it's possible to boot from the network. This system is called PXE.

Why would I want to boot from the network?

  • For installation of a computer without using CDs/DVD's
  • For thin clients
  • For booting diagnostic software

    • What is needed for PXE Boot?

  • a network card that supports PXE
  • a bios that supports plugin boot cards
  • a DHCP server
  • a TFTP server
  • some (open source) software you want to run

    • How to set up PXE boot?

    As I'm running (a variant of) RedHat Linux, I only cover how to set up PXE boot using Linux components. But there are Windows solutions as well. (Google it!)

    Step 1: set up DHCP

    When the NIC boots, it needs to get IP settings. Setup dhcp as usual. Now add these lines to the configuration:
    next-server 192.168.1.254;
    filename "/pxelinux.0";
    In the place of 192.168.1.254, you need to enter your own tftp server address.

    On my RH system, I installed the dhcp server using yum install dhcp, then configured /etc/dhcpd.conf as follows:

    ddns-update-style ad-hoc;
    authoritative;
    log-facility local0;
    default-lease-time 86400;
    max-lease-time 86400;
    subnet 192.168.1.0 netmask 255.255.255.0{
    range 192.168.1.100 192.168.1.200; #limited range
    option subnet-mask 255.255.255.0;
    option broadcast-address 192.168.1.255;
    option routers 192.168.1.254;
    option domain-name-servers 192.168.1.254;
    option domain-name "lan";
    next-server 192.168.1.254;
    filename "/pxelinux.0";
    }

    Step 2: set up TFTP

    Download and install a tftp server. Most Linuxes ship their own, which you can install using yum (RedHat), yast (SuSE), apt-get (debian/ubuntu) or similar.

    On my RedHat, I install a tftp server by running yum install tftp-server. Then I enable it using /sbin/chkconfig tftp on and reload xinetd: /sbin/service xinetd restart.

    Step 3: download and install syslinux

    On my RedHat system, I install syslinux by running yum install syslinux. I then copy the syslinux.0 file to /tftpboot: cp /usr/lib/syslinux/pxelinux.0 /tftpboot

    Optional: Firewall

    On a default RedHat installation, the firewall is enabled. You may need to open port 67-69 for dhcpd and tftp to function and port 53 for DNS.

    Links

    More details are described on
    http://syslinux.zytor.com/wiki/index.php/PXELINUX

    © GeekLabInfo PXE Boot with old-style dhcp and tftp is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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