Backup DHCP and DNS services in a home network

nospam@example.com (Jos van der Woude) — Sun, 25 Mar 2012 09:21:59 +0000

Summary

Goal: Create both primary and (backup) secondary DHCP and DNS services in a small home network.

Needed: one Linux server, one Windows machine and one DHCP capable router with a telnet interface.

Assumption: some programming experience.

Contra indication: not necessary when two Linux servers are available.

Alternative option: Dual DHCP DNS server, sourceforge.net/projects/dhcp-dns-server/files/.

Note: IP addresses, domain names, user names and passwords used here, do not reflect the actual setup.

Overview

My home network consists of one server running Linux, a number of wired clients running on Microsoft or Apple operating systems and an seemingly ever growing number of wireless clients running on a variety of platforms. The network infrastructure consists of a managed switch, a dual WAN router with wireless AP, a separate second wireless AP, a cable modem and a ADSL modem. The server is running both ISC DHCPD and ISC Bind providing crucial DHCP and DNS service to clients in the network.

The goal is to design the network in such a way that when the server is down (for whatever reason) Internet service to known clients is not interrupted. Specifically, known clients are still able to receive DHCP leases and resolve private domain names to IP addresses and vice versa. Obviously other services the server may provide, e.g. smb shares, are interrupted.

To achieve the stated goal it is necessary to have secondary DHCP and DNS services in case the primary services on the Linux server fail. Figure 1 outlines the design.

Figure 1 DHCP and DNS services and their backups

Read whole article for the details of the setup.

Installing The Link Layer Topology Discovery (LLTD) Protocol Responder For Linux

nospam@example.com (Jos van der Woude) — Thu, 25 Aug 2011 09:17:31 +0000

How to make your Linux server appear on the Windows Vista/7 network map like in the picture below.

It is easy to find info on the net on how to install the lld2d responder on a linux server. However, if the Microsoft provided Sample Code is used as is, your linux box is represented as a wireless AP/switch on the map. This is so because in the sample code information is encoded that defines the machine as a wireless AP/switch. You must change this to reflect the fact that your linux box is wired and not a multifunction switch/bridge. This is not hard to do, see the instructions below. For the details you have to read the protocol specification at: Link Layer Topology Discovery Protocol. Not to worry, this is only for the die-hards ...

Instructions

1. Get the Rally-LLTD-PortingKit.exe. Unpack and copy folder to a suitable directory on your Linux server. cd to the Sample Code directory

2. Add the line: #include <limits.h> to src/state.c just after the line #include <assert.h>

3. Edit the file src/osl-linux.c . Make all TLV get-functions relating to wireless/multifunction devices return a simple constant: TLV_GET_FAILED. The functions you must edit are those with the numbers: 5,6,8,9,A,D,14,15,19 and 1A. Do not touch any of the other functions. THIS IS THE CRUCIAL STEP.

4. cd to the native-linux directory and run make. Install the resulting executable lld2d to /usr/sbin

5. Use an icon editor to make a Windows 48x48 pixel icon of your choice. I have used tux, obviously. Copy this *.ico file to /etc on your server.

6. Edit lld2d.conf to set proper path and name for your own icon

7. Copy lld2d.conf to /etc also

8. Run /usr/sbin/lld2d eth0. If necessary replace eth0 with your own ethernet device

9. Optionally create an init script.

10. Generate a new network map in Windows 7/Vista and watch the results in awe ...

Have fun!

Stuff Jos van der Woude cares about - Geeky stuff

Backup DHCP and DNS services in a home network

Summary

Overview

Installing The Link Layer Topology Discovery (LLTD) Protocol Responder For Linux

Instructions