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English
A bridge works by scanning the addresses of <acronym>MAC</acronym> level (Ethernet addresses) of the devices connected to each of its network interfaces and then forwarding the traffic between the two networks only if the source and the destination are on different segments. Under many points of view a bridge is similar to an Ethernet switch with only two ports.
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Context English Spanish State
_ translator-credits Sergio Carlavilla carlavilla@FreeBSD.org, 2020
Filtering Bridges Filtering Bridges
<email>ale@FreeBSD.org</email> <email>ale@FreeBSD.org</email>
<personname><firstname>Alex</firstname><surname>Dupre</surname></personname><affiliation> <_:address-1/> </affiliation> <personname><firstname>Alex</firstname><surname>Dupre</surname></personname><affiliation> <_:address-1/> </affiliation>
FreeBSD is a registered trademark of the FreeBSD Foundation. FreeBSD is a registered trademark of the FreeBSD Foundation.
3Com and HomeConnect are registered trademarks of 3Com Corporation. 3Com and HomeConnect are registered trademarks of 3Com Corporation.
Intel, Celeron, Centrino, Core, EtherExpress, i386, i486, Itanium, Pentium, and Xeon are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. Intel, Celeron, Centrino, Core, EtherExpress, i386, i486, Itanium, Pentium, and Xeon are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries.
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this document, and the FreeBSD Project was aware of the trademark claim, the designations have been followed by the <quote>™</quote> or the <quote>®</quote> symbol. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this document, and the FreeBSD Project was aware of the trademark claim, the designations have been followed by the <quote>™</quote> or the <quote>®</quote> symbol.
$FreeBSD: head/en_US.ISO8859-1/articles/filtering-bridges/article.xml 53717 2019-12-29 14:13:50Z carlavilla $ $FreeBSD$
Often it is useful to divide one physical network (like an Ethernet) into two separate segments without having to create subnets, and use a router to link them together. The device that connects the two networks in this way is called a bridge. A FreeBSD system with two network interfaces is enough in order to act as a bridge. A menudo es útil dividir una red física (por ejemplo una Ethernet) en dos segmentos separados sin tener que crear subredes y usar un router para vincularlas. El dispositivo que conecta las dos redes se llama bridge. Un sistema FreeBSD con dos interfaces de red es suficiente para actuar como bridge.
A bridge works by scanning the addresses of <acronym>MAC</acronym> level (Ethernet addresses) of the devices connected to each of its network interfaces and then forwarding the traffic between the two networks only if the source and the destination are on different segments. Under many points of view a bridge is similar to an Ethernet switch with only two ports. Un bridge funciona escaneando las direcciones del nivel <acronym>MAC</acronym> (direcciones Ethernet) de los dispositivos conectados a cada una de sus interfaces de red y luego reenvía el tráfico entre las dos redes solo si la fuente y el destino están en diferentes segmentos. En muchos aspectos, un bridge es similar a un switch de Ethernet con solo dos puertos.
Why use a filtering bridge? ¿Por qué utilizar un bridge que haga filtrado?
More and more frequently, thanks to the lowering costs of broad band Internet connections (xDSL) and also because of the reduction of available IPv4 addresses, many companies are connected to the Internet 24 hours on 24 and with few (sometimes not even a power of 2) IP addresses. In these situations it is often desirable to have a firewall that filters incoming and outgoing traffic from and towards Internet, but a packet filtering solution based on router may not be applicable, either due to subnetting issues, the router is owned by the connectivity supplier (<acronym>ISP</acronym>), or because it does not support such functionalities. In these scenarios the use of a filtering bridge is highly advised. Sucede con bastante frecuencia que, gracias a la reducción del coste de las conexiones de banda ancha a Internet (xDSL) y a la reducción de las direcciones IPv4 disponibles, muchas empresas están conectadas a Internet las 24 horas del día y con pocas (a veces ni siquiera dos) direcciones IP. A menudo en estas situaciones es necesario tener un firewall (también conocido como cortafuegos) que filtre el tráfico entrante y saliente desde y hacia Internet, pero una solución de filtrado de paquetes puede que no sea posible posible, ya sea por problemas de subredes, porque el router sea de propiedad del proveedor de servicios de internet (<acronym>ISP</acronym>), o porque no admite tales funcionalidades. En escenarios como estos se recomienda el uso de un brigde que realice el filtrado.
A bridge-based firewall can be configured and inserted between the xDSL router and your Ethernet hub/switch without any IP numbering issues. Una buena solución sería configurar un firewall basado en un bridge. Lo instalaremos entre el router xDSL y su hub/switch Ethernet, evitando así problemas de numeración IP.
How to Install Proceso de instalación
Adding bridge functionalities to a FreeBSD system is not difficult. Since 4.5 release it is possible to load such functionalities as modules instead of having to rebuild the kernel, simplifying the procedure a great deal. In the following subsections I will explain both installation ways. No es difícil añadir funcionalidades de brigde a un sistema FreeBSD. Desde la versión 4.5 es posible cargar funcionalidades como módulos en lugar de tener que volver a compilar el kernel, lo cual simplifica mucho el procedimiento. En las siguientes subsecciones explicaré ambas formas de instalación.
<emphasis>Do not</emphasis> follow both instructions: a procedure <emphasis>excludes</emphasis> the other one. Select the best choice according to your needs and abilities. <emphasis>No</emphasis> siga ambas instrucciones: un procedimiento <emphasis>excluye</emphasis> el otro. Seleccione la mejor opción de acuerdo a sus necesidades y habilidades.
Before going on, be sure to have at least two Ethernet cards that support the promiscuous mode for both reception and transmission, since they must be able to send Ethernet packets with any address, not just their own. Moreover, to have a good throughput, the cards should be PCI bus mastering cards. The best choices are still the Intel <trademark>EtherExpress</trademark> Pro, followed by the <trademark class="registered">3Com</trademark> 3c9xx series. To simplify the firewall configuration it may be useful to have two cards of different manufacturers (using different drivers) in order to distinguish clearly which interface is connected to the router and which to the inner network. Antes de continuar asegúrese de tener al menos dos tarjetas Ethernet que admitan el modo promiscuo tanto para la recepción como para la transmisión, ya que deben poder enviar paquetes Ethernet con cualquier dirección, no solo la suya. Además, para tener una buena tasa de transferencia, las tarjetas deben ser tarjetas del bus PCI. Las mejores opciones siguen siendo Intel <trademark>EtherExpress</trademark> Pro, seguida de la <trademark class="registered">3Com</trademark> 3c9xx series. Para simplificar la configuración del firewall, puede ser útil tener dos tarjetas de diferentes fabricantes (con diferentes controladores) para distinguir claramente qué interfaz está conectada al router y cuál a la red interna.
Kernel Configuration Configuración del kernel
So you have decided to use the older but well tested installation method. To begin, you have to add the following rows to your kernel configuration file: Si sigue este método es porque ha decidido utilizar el método de instalación más antiguo y también el que ha sido probado más. Para empezar, debe agregar las siguientes líneas a su archivo de configuración del kernel:
options BRIDGE
options IPFIREWALL
options IPFIREWALL_VERBOSE 		options BRIDGE
options IPFIREWALL
options IPFIREWALL_VERBOSE
The first line is to compile the bridge support, the second one is the firewall and the third one is the logging functions of the firewall. La primera línea añade el soporte para el bridge, la segunda añade la compatibilidad con el firewall y la tercera se refiere a las funciones de logging del firewall.
Now it is necessary to build and install the new kernel. You may find detailed instructions in the <link xlink:href="@@URL_RELPREFIX@@/doc/en_US.ISO8859-1/books/handbook/kernelconfig-building.html">Building and Installing a Custom Kernel</link> section of the FreeBSD Handbook. Ahora es necesario compilar e instalar el nuevo kernel. Puede encontrar instrucciones detalladas en la sección <link xlink:href="@@URL_RELPREFIX@@/doc/es_ES.ISO8859-1/books/handbook/kernelconfig-building.html">compilar e instalar un kernel personalizado</link> del manual de FreeBSD.
Modules Loading Carga de módulos
If you have chosen to use the new and simpler installation method, the only thing to do now is add the following row to <filename>/boot/loader.conf</filename>: Si ha elegido usar el nuevo método de instalación (más simple), lo único que debe hacer es añadir la siguiente línea a <filename> /boot/loader.conf </filename>:
bridge_load="YES" bridge_load="YES"

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FreeBSD Doc (Archived) / articles_filtering-bridge — Spanish

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(itstool) path: abstract/para
Source string location
article.translate.xml:41
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a year ago
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a year ago
Translation file
articles/es_ES/filtering-bridges.po, string 11