Dnsmasq
Encyclopedia
The homepage describes dnsmasq as a lightweight, easy to configure, DNS
forwarder, DHCP
and TFTP server, designed to provide DNS (and optionally DHCP and TFTP) services to a small-scale network
. It can serve the names of local machines which are not in the global DNS. The DHCP server integrates with the DNS server and allows machines with DHCP-allocated addresses to appear in the DNS with names configured either in each host or in a central configuration file. Dnsmasq supports static and dynamic DHCP leases and BOOTP
for network booting of diskless machines.
The developers of dnsmasq targeted home networks using NAT
and connected to the internet via a modem
, cable-modem or ADSL
connection. But the system would function well in any small network where low resource-use and ease of configuration are important.
Supported platforms include Linux
(with glibc or uClibc
), BSD
and Mac OS X
.
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
forwarder, DHCP
Dynamic Host Configuration Protocol
The Dynamic Host Configuration Protocol is a network configuration protocol for hosts on Internet Protocol networks. Computers that are connected to IP networks must be configured before they can communicate with other hosts. The most essential information needed is an IP address, and a default...
and TFTP server, designed to provide DNS (and optionally DHCP and TFTP) services to a small-scale network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
. It can serve the names of local machines which are not in the global DNS. The DHCP server integrates with the DNS server and allows machines with DHCP-allocated addresses to appear in the DNS with names configured either in each host or in a central configuration file. Dnsmasq supports static and dynamic DHCP leases and BOOTP
BOOTP
In computer networking, the Bootstrap Protocol, or BOOTP, is a network protocol used by a network client to obtain an IP address from a configuration server. The BOOTP protocol was originally defined in RFC 951....
for network booting of diskless machines.
The developers of dnsmasq targeted home networks using NAT
Network address translation
In computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
and connected to the internet via a modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
, cable-modem or ADSL
Asymmetric Digital Subscriber Line
Asymmetric digital subscriber line is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice...
connection. But the system would function well in any small network where low resource-use and ease of configuration are important.
Supported platforms include Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
(with glibc or uClibc
UClibc
In computing, uClibc is a small C standard library intended for embedded Linux systems. uClibc was created to support uClinux, a version of Linux not requiring a memory management unit and thus suited for microcontrollers .The project lead is Erik Andersen. The other main contributor is Manuel...
), BSD
Berkeley Software Distribution
Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
.
Features
Dnsmasq provides the following features:- Simple DNS configuration of machines behind the firewallFirewall (computing)A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass....
, independent of the details of an ISP's DNS servers - Clients which try to do DNS lookups while a modem-link to the internet is down will time out immediately.
- Dnsmasq will serve names from the /etc/hosts file (or an alternate). The names of local machines provided in this way can all be addressed without having to maintain /etc/hosts on each machine.
- The integrated DHCP server supports static and dynamic DHCP leases and multiple networks and IP ranges. It works across BOOTP relays and supports DHCP options including RFC 3397 DNS search lists.
- Machines configured via DHCP have their names automatically included in the DNS and the names can be specified by each machine or centrally by associating a name with a MAC addressMAC addressA Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
in the dnsmasq config file. - Dnsmasq caches internet addresses (A records and AAAA records) and address-to-name mappings (PTR records), reducing the load on upstream servers and improving performance (especially on modem connections).
- Users can configure dnsmasq to automatically pick up the addresses of its upstream nameservers from ppp or dhcp configuration. It will automatically reload this information if it changes. This facility helps maintainers of Linux firewall distributions to automate DNS configuration.
- On IPv6IPv6Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
-enabled boxes, dnsmasq can both talk to upstream servers via IPv6 and offer DNS service via IPv6. On dual-stack (IPv4IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
and IPv6) boxes it talks both protocols and can even act as IPv6-to-IPv4 or IPv4-to-IPv6 forwarder. - Users can configure dnsmasq to send queries for certain domains to upstream servers handling only those domains. This makes integration with private DNS systems easy.
- Dnsmasq supports MX recordMX recordA mail exchanger record is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available...
s and can return MX records for any or all local machines. - Some internet service-providers rewrite the NXDOMAIN (domain does not exist) responses from DNS servers. This forces web browsers to a search page whenever a user attempts to browse to a domain that does not exist. Dnsmasq can filter these "bogus nxdomain" records out, preventing this potentially unwanted behavior.
External links
- http://www.thekelleys.org.uk/dnsmasq/doc.html
- http://packages.debian.org/dnsmasq (debian package page)