BIRD User's Guide: Configuration

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## 3. Configuration

## 3.1 Introduction

BIRD is configured using a text configuration file. Upon startup, BIRD reads prefix/etc/bird.conf (unless the `-c` command line option is given). Configuration may be changed at user's request: if you modify the config file and then signal BIRD with `SIGHUP`, it will adjust to the new config. Then there's the client which allows you to talk with BIRD in an extensive way.

In the config, everything on a line after `#` or inside `/* */` is a comment, whitespace characters are treated as a single space. If there's a variable number of options, they are grouped using the `{ }` brackets. Each option is terminated by a `;`. Configuration is case sensitive.

Here is an example of a simple config file. It enables synchronization of routing tables with OS kernel, scans for new network interfaces every 10 seconds and runs RIP on all network interfaces found.

    protocol kernel {
            persist;                # Don't remove routes on BIRD shutdown
            scan time 20;           # Scan kernel routing table every 20 seconds
            export all;             # Default is export none
    }

    protocol device {
            scan time 10;           # Scan interfaces every 10 seconds
    }

    protocol rip {
            export all;
            import all;
            interface "*";
    }

## 3.2 Global options

`log "filename"|syslog [name name]|stderr all|{ list of classes }`

  Set logging of messages having the given class (either `all` or `{ error, trace }` etc.) into selected destination (a file specified as a filename string, syslog with optional name argument, or the stderr output). Classes are: `info`, `warning`, `error` and `fatal` for messages about local problems, `debug` for debugging messages, `trace` when you want to know what happens in the network, `remote` for messages about misbehavior of remote machines, `auth` about authentication failures, `bug` for internal BIRD bugs. You may specify more than one `log` line to establish logging to multiple destinations. Default: log everything to the system log.

`debug protocols all|off|{ states, routes, filters, interfaces, events, packets }`

  Set global defaults of protocol debugging options. See `debug` in the following section. Default: off.

`debug commands number`

  Control logging of client connections (0 for no logging, 1 for logging of connects and disconnects, 2 and higher for logging of all client commands). Default: 0.

`mrtdump "filename"`

  Set MRTdump file name. This option must be specified to allow MRTdump feature. Default: no dump file.

`mrtdump protocols all|off|{ states, messages }`

  Set global defaults of MRTdump options. See `mrtdump` in the following section. Default: off.

`filter name local variables{ commands }`

  Define a filter. You can learn more about filters in the following chapter.

`function name (parameters) local variables { commands }`

  Define a function. You can learn more about functions in the following chapter.

`protocol rip|ospf|bgp|... [name] { protocol options }`

  Define a protocol instance called `name` (or with a name like "rip5" generated automatically if you don't specify any `name`). You can learn more about configuring protocols in their own chapters. You can run more than one instance of most protocols (like RIP or BGP). By default, no instances are configured.

`define constant = (expression)|number|IP address`

  Define a constant. You can use it later in every place you could use a simple integer or an IP address.

`router id IPv4 address`

  Set BIRD's router ID. It's a world-wide unique identification of your router, usually one of router's IPv4 addresses. Default: in IPv4 version, the lowest IP address of a non-loopback interface. In IPv6 version, this option is mandatory.

`listen bgp [address address] [port port] [v6only]`

  This option allows to specify address and port where BGP protocol should listen. It is global option as listening socket is common to all BGP instances. Default is to listen on all addresses (0.0.0.0) and port 179. In IPv6 mode, option `v6only` can be used to specify that BGP socket should listen to IPv6 connections only. This is needed if you want to run both bird and bird6 on the same port.

`timeformat route|protocol|base|log "format1" [limit> "format2"]`

  This option allows to specify a format of date/time used by BIRD. The first argument specifies for which purpose such format is used. `route` is a format used in 'show route' command output, `protocol` is used in 'show protocols' command output, `base` is used for other commands and `log` is used in a log file.

  "format1" is a format string using strftime(3) notation (see man strftime for details). limit> and "format2" allow to specify the second format string for times in past deeper than limit seconds. There are two shorthands: `iso long` is a ISO 8601 datetime format (YYYY-MM-DD hh:mm:ss) that can be also specified using `"%F %T"`. `iso short` is a variant of ISO 8601 that uses just the time format (hh:mm:ss) for near times (up to 20 hours in the past) and the date format (YYYY-MM-DD) for far times. This is a shorthand for `"%T" 72000 "%F"`.

  By default, BIRD uses an short, ad-hoc format for `route` and `protocol` times, and a `iso long` similar format (DD-MM-YYYY hh:mm:ss) for `base` and `log`. These defaults are here for a compatibility with older versions and might change in the future.

`table name`

  Create a new routing table. The default routing table is created implicitly, other routing tables have to be added by this command.

`eval expr`

  Evaluates given filter expression. It is used by us for testing of filters.

## 3.3 Protocol options

For each protocol instance, you can configure a bunch of options. Some of them (those described in this section) are generic, some are specific to the protocol (see sections talking about the protocols).

Several options use a `switch` argument. It can be either `on`, `yes` or a numeric expression with a non-zero value for the option to be enabled or `off`, `no` or a numeric expression evaluating to zero to disable it. An empty `switch` is equivalent to `on` ("silence means agreement").

`preference expr`

  Sets the preference of routes generated by this protocol. Default: protocol dependent.

`disabled switch`

  Disables the protocol. You can change the disable/enable status from the command line interface without needing to touch the configuration. Disabled protocols are not activated. Default: protocol is enabled.

`debug all|off|{ states, routes, filters, interfaces, events, packets }`

  Set protocol debugging options. If asked, each protocol is capable of writing trace messages about its work to the log (with category `trace`). You can either request printing of `all` trace messages or only of the types selected: `states` for protocol state changes (protocol going up, down, starting, stopping etc.), `routes` for routes exchanged with the routing table, `filters` for details on route filtering, `interfaces` for interface change events sent to the protocol, `events` for events internal to the protocol and `packets` for packets sent and received by the protocol. Default: off.

`mrtdump all|off|{ states, messages }`

  Set protocol MRTdump flags. MRTdump is a standard binary format for logging information from routing protocols and daemons. These flags control what kind of information is logged from the protocol to the MRTdump file (which must be specified by global `mrtdump` option, see the previous section). Although these flags are similar to flags of `debug` option, their meaning is different and protocol-specific. For BGP protocol, `states` logs BGP state changes and `messages` logs received BGP messages. Other protocols does not support MRTdump yet.

`router id IPv4 address`

  This option can be used to override global router id for a given protocol. Default: uses global router id.

`import all | none | filter name | filter { filter commands } | where filter expression`

  Specify a filter to be used for filtering routes coming from the protocol to the routing table. `all` is shorthand for `where true` and `none` is shorthand for `where false`. Default: `all`.

`export filter`

  This is similar to the `import` keyword, except that it works in the direction from the routing table to the protocol. Default: `none`.

`description "text"`

  This is an optional description of the protocol. It is displayed as a part of the output of 'show route all' command.

`table name`

  Connect this protocol to a non-default routing table.

There are several options that give sense only with certain protocols:

`interface [-] [ "mask" ] [ prefix ] [, ...] [ { option ; [...] } ]`

  Specifies a set of interfaces on which the protocol is activated with given interface-specific options. A set of interfaces specified by one interface option is described using an interface pattern. The interface pattern consists of a sequence of clauses (separated by commas), each clause may contain a mask, a prefix, or both of them. An interface matches the clause if its name matches the mask (if specified) and its address matches the prefix (if specified). Mask is specified as shell-like pattern.

  An interface matches the pattern if it matches any of its clauses. If the clause begins with `-`, matching interfaces are excluded. Patterns are parsed left-to-right, thus `interface "eth0", -"eth*", "*";` means eth0 and all non-ethernets.

  An interface option can be used more times with different interfaces-specific options, in that case for given interface the first matching interface option is used.

  This option is allowed in Direct, OSPF and RIP protocols, but in OSPF protocol it is used in `area` subsection.

  Default: none.

  Examples:

  `interface "*" { type broadcast; };` - start the protocol on all interfaces with `type broadcast` option.

  `interface "eth1", "eth4", "eth5" { type pointopoint; };` - start the protocol on enumerated interfaces with `type pointopoint` option.

  `interface -192.168.1.0/24, 192.168.0.0/16;` - start the protocol on all interfaces that have address from 192.168.0.0/16, but not from 192.168.1.0/24.

  `interface -192.168.1.0/24, 192.168.0.0/16;` - start the protocol on all interfaces that have address from 192.168.0.0/16, but not from 192.168.1.0/24.

  `interface "eth*" 192.168.1.0/24;` - start the protocol on all ethernet interfaces that have address from 192.168.1.0/24.

`password "password" [ { id num; generate from time; generate to time; accept from time; accept to time; } ]`

  Specifies a password that can be used by the protocol. Password option can be used more times to specify more passwords. If more passwords are specified, it is a protocol-dependent decision which one is really used. Specifying passwords does not mean that authentication is enabled, authentication can be enabled by separate, protocol-dependent `authentication` option.

  This option is allowed in OSPF and RIP protocols. BGP has also `password` option, but it is slightly different and described separately.

  Default: none.

Password option can contain section with some (not necessary all) password sub-options:

`id num`

  ID of the password, (0-255). If it's not used, BIRD will choose ID based on an order of the password item in the interface. For example, second password item in one interface will have default ID 2. ID is used by some routing protocols to identify which password was used to authenticate protocol packets.

`generate from "time"`

  The start time of the usage of the password for packet signing. The format of `time` is `dd-mm-yyyy HH:MM:SS`.

`generate to "time"`

  The last time of the usage of the password for packet signing.

`accept from "time"`

  The start time of the usage of the password for packet verification.

`accept to "time"`

  The last time of the usage of the password for packet verification.

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