Global options

protocol-group group

This specifies the link-local multicast address to be used by the protocol, and is equivalent to the command-line option -m.

protocol-port port

This specifies the UDP port number to be used by the protocol, and is equivalent to the command-line option -p.

kernel-priority priority

This specifies the priority value used when installing routes into the kernel, and is equivalent to the command-line option -k.

reflect-kernel-metric {true|false}

Reflect route metrics as kernel priorities. The priority effectively used is kernel-priority + metric.

allow-duplicates priority

This allows duplicating external routes when their kernel priority is at least priority. Do not use this option unless you know what you are doing, as it can cause persistent route flapping.

random-id {true|false}

This specifies whether to use a random router-id, and is equivalent to the command-line option -r.

ipv6-subtrees {true|false}

This specifies whether to use native source-specific IPv6 forwarding rather than multiple routing tables. The default is chosen automatically depending on the kernel version.

debug level

This specifies the debugging level, and is equivalent to the command-line option -d.

local-port port

This specifies the TCP port on which babeld will listen for connections from a configuration client in read-only mode, and is equivalent to the command-line option -g.

local-port-readwrite port

This specifies the TCP port on which babeld will listen for connections from a configuration client in read-write mode, and is equivalent to the command-line option -G. This allows any local user to change babeld's configuration, and may therefore be a security issue.

local-path path

This specifies the filesystem path to a socket on which babeld will listen for connections from a configuration client in read-only mode, and is equivalent to the command-line option -g.

local-path-readwrite path

This specifies the filesystem path to a socket on which babeld will listen for connections from a configuration client in read-write mode, and is equivalent to the command-line option -G. Any user with write access to that socket will be able to change babeld's configuration.

export-table table

This specifies the kernel routing table to use for routes inserted by babeld, and is equivalent to the command-line option -t.

import-table table

This specifies a kernel routing table from which routes are redistributed by babeld, and can be specified multiple times with a cumulative effect. This is equivalent to the command-line option -T.

link-detect {true|false}

This specifies whether to use carrier sense for determining interface availability, and is equivalent to the command-line option -l.

diversity {true|false|kind}

This specifies the diversity algorithm to use; true is equivalent to kind 3. The default is false (do not use any diversity algorithm).

diversity-factor factor

This specifies by how much the cost of non-interfering routes should be multiplied, in units of 1/256. The default is 128 (division by 2).

smoothing-half-life seconds

This specifies the half-life in seconds of the exponential decay used for smoothing metrics for performing route selection, and is equivalent to the command-line option -M.

daemonise {true|false}

This specifies whether to daemonize at startup, and is equivalent to the command-line option -D.

skip-kernel-setup {true|false}

If this flag is set, no kernel (sysctl) setup is performed on startup, and it is assumed that enabling forwarding, disabling redirects and disabling the reverse-path filter is performed by other means. This can be useful when running in environments where system permissions prevent setting kernel parameters, for instance without root permissions or inside a Linux container.

router-id id

Specify the router-id explicitly, as a modified EUI-64 or a MAC-48 address. If two nodes have the same router-id, bad things will happen. Don't use this option unless you know what you are doing.

state-file filename

This specifies the name of the file used for preserving long-term information between invocations of the babeld daemon, and is equivalent to the command-line option -S.

log-file filename

This specifies the name of the file used to log random messages to, and is equivalent to the command-line option -L.

pid-file filename

This specifies the name of the file to which babeld writes out its process id, and is equivalent to the command-line option -I.

Interface configuration

interface name [parameter...]

where name is the name of the interface (something like eth0). The default value of an interface parameter can be specified changed by a line of the form

default [parameter...]

Each parameter can be one of:

type {auto|wired|wireless|tunnel}

The default is auto unless the -w command-line flag was specified.

link-quality {true|false|auto}

This specifies whether link quality estimation should be performed on this interface. The default is to perform link quality estimation on wireless interfaces only.

split-horizon {true|false|auto}

This specifies whether to perform split-horizon processing on this interface. The default is to perform split-horizon processing on on wired interfaces, unless the -s flag was set.

rxcost cost

This defines the cost of receiving frames on the given interface under ideal conditions (no packet loss); how this relates to the actual cost used for computing metrics of routes going through this interface depends on whether link quality estimation is being done. The default is 256 if the interface is wireless, and 96 otherwise.

channel channel

Sets the channel for this interface. The value channel can be either an integer, or one of the strings interfering or noninterfering. The default is to autodetect the channel number for wireless interfaces, and noninterfering for other interfaces.

faraway {true|false}

This specifies whether the network is "far away", in the sense that networks behind it don't interfere with networks in front of it. By default, networks are not far away.

hello-interval interval

This defines the interval between hello packets sent on this interface. The default is specified with the -h and -H command-line flags.

update-interval interval

This defines the interval between full routing table dumps sent on this interface; since Babel uses triggered updates and doesn't count to infinity, this can be set to a fairly large value, unless significant packet loss is expected. The default is four times the hello interval.

enable-timestamps {true|false}

Enable sending timestamps with each Hello and IHU message in order to compute RTT values. The default is true for tunnel interfaces, and false otherwise.

unicast {true|false}

Send multiple copies of TLVs other than Hellos to all neighbours rather than sending a single multicast packet. The default is false.

rfc6126-compatible {true|false}

Disable some features that are incompatible with RFC 6126 (the older version of the Babel protocol), such as source-specific routing and RTT estimation over unicast. The default is false.

rtt-decay decay

This specifies the decay factor for the exponential moving average of RTT samples, in units of 1/256. Must be between 1 and 256, inclusive. Higher values discard old samples faster. The default is 42.

rtt-min rtt

This specifies the minimum RTT, in milliseconds, starting from which we increase the cost to a neighbour. The additional cost is linear in (rtt - rtt-min). The default is 10 ms.

rtt-max rtt

This specifies the maximum RTT, in milliseconds, above which we don't increase the cost to a neighbour. The default is 120 ms.

max-rtt-penalty cost

This specifies the maximum cost added to a neighbour because of RTT, i.e. when the RTT is higher or equal than rtt-max. The default is 96 if the interface is of type tunnel, and 0 otherwise.

Filtering rules

filter selector... action

Filter specifies the filter to which this entry will be added, and can be one of in (applied to routes learned from Babel neighbours), out (applied to routes announced to Babel neighbours), redistribute (applied to routes redistributed from the kernel), or install (applied to routes installed into the kernel).

Each selector specifies the conditions under which the given statement matches. It can be one of

ip prefix

This entry only applies to routes in the given prefix.

eq plen

This entry only applies to routes with a prefix length equal to plen.

le plen

This entry only applies to routes with a prefix length less or equal to plen.

ge plen

This entry only applies to routes with a prefix length greater or equal to plen.

src-ip prefix

This entry only applies to routes with a source prefix in the given prefix.

src-eq plen

This entry only applies to routes with a source prefix length equal to plen.

src-le plen

This entry only applies to routes with a source prefix length less or equal to plen.

src-ge plen

This entry only applies to routes with a source prefix length greater or equal to plen.

neigh address

This entry only applies to routes learned from a neighbour with link-local address address.

id id

This entry only applies to routes originated by a router with router-id id.

proto p

This entry only applies to kernel routes with kernel protocol number p. If neither proto nor local is specified, this entry applies to all non-local kernel routes with a protocol different from "boot".

local

This entry only applies to local addresses.

if interface

For an input filter, this specifies the interface over which the route is learned. For an output filter, this specifies the interface over which this route is advertised. For a redistribute statement, this specifies the interface over which the route forwards packets.

Action specifies the action to be taken when this entry matches. It can have one of the following values:

allow

Allow this route, without changing its metric (or setting its metric to 0 in case of a redistribute filter).

deny

Ignore this route.

metric value

For an input or output filter, allow this route after increasing its metric by value. For a redistribute filter, redistribute this route with metric value.

src-prefix prefix

For a redistribute filter, set the source prefix of this route to prefix.

table table

In an install filter, specify the kernel routing table to use. For source-specific routes, this only works reliably for IPv6, and only when ipv6-subtrees is true.

pref-src ip

Specify the preferred source address to use with this route. Only useful in an install filter.

If action is not specified, it defaults to allow.

By default, babeld redistributes all local addresses, and no other routes. In order to make sure that only the routes you specify are redistributed, you should include the line

redistribute local deny

as the last line in your configuration file.

Source-specific routing

redistribute src-prefix 2001:DB8:0:1::/64

For more information about source-specific routing, please see

Matthieu Boutier and Juliusz Chroboczek. Source-sensitive routing. In Proc. IFIP Networking 2015. 2015.

available online at

http://arxiv.org/pdf/1403.0445v4.pdf