doc/user/babeld.rst

   1 .. _babel:
   2
   3 *****
   4 Babel
   5 *****
   6
   7 Babel is an interior gateway protocol that is suitable both for wired networks
   8 and for wireless mesh networks.  Babel has been described as 'RIP on speed' --
   9 it is based on the same principles as RIP, but includes a number of refinements
  10 that make it react much faster to topology changes without ever counting to
  11 infinity, and allow it to perform reliable link quality estimation on wireless
  12 links.  Babel is a double-stack routing protocol, meaning that a single Babel
  13 instance is able to perform routing for both IPv4 and IPv6.
  14
  15 FRR implements Babel as described in :rfc:`6126`.
  16
  17 .. _configuring-babeld:
  18
  19 Configuring babeld
  20 ==================
  21
  22 The *babeld* daemon can be invoked with any of the common
  23 options (:ref:`common-invocation-options`).
  24
  25 The *zebra* daemon must be running before *babeld* is
  26 invoked. Also, if *zebra* is restarted then *babeld*
  27 must be too.
  28
  29 Configuration of *babeld* is done in its configuration file
  30 :file:`babeld.conf`.
  31
  32 .. _babel-configuration:
  33
  34 Babel configuration
  35 ===================
  36
  37 .. index::
  38    single: router babel
  39    single: no router babel
  40
  41 .. clicmd:: [no] router babel
  42
  43    Enable or disable Babel routing.
  44
  45 .. index::
  46    single: babel resend-delay (20-655340)
  47    single: no babel resend-delay [(20-655340)]
  48
  49 .. clicmd:: [no] babel resend-delay (20-655340)
  50
  51    Specifies the time after which important messages are resent when
  52    avoiding a black-hole. The default is 2000 ms.
  53
  54 .. index::
  55    single: babel diversity
  56    single: no babel diversity
  57
  58 .. clicmd:: [no] babel diversity
  59
  60    Enable or disable routing using radio frequency diversity.  This is
  61    highly recommended in networks with many wireless nodes.
  62    If you enable this, you will probably want to set `babel
  63    diversity-factor` and `babel channel` below.
  64
  65 .. index:: babel diversity-factor (1-256)
  66
  67 .. clicmd:: babel diversity-factor (1-256)
  68
  69    Sets the multiplicative factor used for diversity routing, in units of
  70    1/256; lower values cause diversity to play a more important role in
  71    route selection.  The default it 256, which means that diversity plays
  72    no role in route selection; you will probably want to set that to 128
  73    or less on nodes with multiple independent radios.
  74
  75 .. index::
  76    single: network IFNAME
  77    single: no network IFNAME
  78
  79 .. clicmd:: no network IFNAME
  80
  81    Enable or disable Babel on the given interface.
  82
  83 .. index:: babel <wired|wireless>
  84
  85 .. clicmd:: babel <wired|wireless>
  86
  87    Specifies whether this interface is wireless, which disables a number
  88    of optimisations that are only correct on wired interfaces.
  89    Specifying `wireless` (the default) is always correct, but may
  90    cause slower convergence and extra routing traffic.
  91
  92 .. index::
  93    single: babel split-horizon
  94    single: no babel split-horizon
  95
  96 .. clicmd:: [no] babel split-horizon
  97
  98    Specifies whether to perform split-horizon on the interface.  Specifying
  99    ``no babel split-horizon`` is always correct, while ``babel
 100    split-horizon`` is an optimisation that should only be used on symmetric
 101    and transitive (wired) networks.  The default is ``babel split-horizon``
 102    on wired interfaces, and ``no babel split-horizon`` on wireless
 103    interfaces.  This flag is reset when the wired/wireless status of an
 104    interface is changed.
 105
 106 .. index:: babel hello-interval (20-655340)
 107
 108 .. clicmd:: babel hello-interval (20-655340)
 109
 110    Specifies the time in milliseconds between two scheduled hellos.  On
 111    wired links, Babel notices a link failure within two hello intervals;
 112    on wireless links, the link quality value is reestimated at every
 113    hello interval.  The default is 4000 ms.
 114
 115 .. index:: babel update-interval (20-655340)
 116
 117 .. clicmd:: babel update-interval (20-655340)
 118
 119    Specifies the time in milliseconds between two scheduled updates.  Since
 120    Babel makes extensive use of triggered updates, this can be set to fairly
 121    high values on links with little packet loss.  The default is 20000 ms.
 122
 123 .. index::
 124    single: babel channel (1-254)
 125    single: babel channel interfering
 126    single: babel channel noninterfering
 127
 128 .. clicmd:: babel channel (1-254)
 129 .. clicmd:: babel channel interfering
 130 .. clicmd:: babel channel noninterfering
 131
 132    Set the channel number that diversity routing uses for this interface (see
 133    `babel diversity` above).  Noninterfering interfaces are assumed to only
 134    interfere with themselves, interfering interfaces are assumed to interfere
 135    with all other channels except noninterfering channels, and interfaces with
 136    a channel number interfere with interfering interfaces and interfaces with
 137    the same channel number.  The default is ``babel channel interfering`` for
 138    wireless interfaces, and ``babel channel noninterfering`` for wired
 139    interfaces.  This is reset when the wired/wireless status of an interface is
 140    changed.
 141
 142 .. index:: babel rxcost (1-65534)
 143
 144 .. clicmd:: babel rxcost (1-65534)
 145
 146    Specifies the base receive cost for this interface.  For wireless
 147    interfaces, it specifies the multiplier used for computing the ETX
 148    reception cost (default 256); for wired interfaces, it specifies the
 149    cost that will be advertised to neighbours.  This value is reset when
 150    the wired/wireless attribute of the interface is changed.
 151
 152 .. note::
 153    Do not use this command unless you know what you are doing; in most
 154    networks, acting directly on the cost using route maps is a better
 155    technique.
 156
 157 .. index:: babel rtt-decay (1-256)
 158
 159 .. clicmd:: babel rtt-decay (1-256)
 160
 161    This specifies the decay factor for the exponential moving average of
 162    RTT samples, in units of 1/256.  Higher values discard old samples
 163    faster.  The default is 42.
 164
 165 .. index:: babel rtt-min (1-65535)
 166
 167 .. clicmd:: babel rtt-min (1-65535)
 168
 169    This specifies the minimum RTT, in milliseconds, starting from which we
 170    increase the cost to a neighbour. The additional cost is linear in
 171    (rtt - rtt-min).  The default is 100 ms.
 172
 173 .. index:: babel rtt-max (1-65535)
 174
 175 .. clicmd:: babel rtt-max (1-65535)
 176
 177    This specifies the maximum RTT, in milliseconds, above which we don't
 178    increase the cost to a neighbour. The default is 120 ms.
 179
 180 .. index:: babel max-rtt-penalty (0-65535)
 181
 182 .. clicmd:: babel max-rtt-penalty (0-65535)
 183
 184    This specifies the maximum cost added to a neighbour because of RTT, i.e.
 185    when the RTT is higher or equal than rtt-max.  The default is 0, which
 186    effectively disables the use of a RTT-based cost.
 187
 188 .. index::
 189    single: babel enable-timestamps
 190    single: no babel enable-timestamps
 191
 192 .. clicmd:: [no] babel enable-timestamps
 193
 194    Enable or disable sending timestamps with each Hello and IHU message in
 195    order to compute RTT values.  The default is `no babel enable-timestamps`.
 196
 197 .. index:: babel resend-delay (20-655340)
 198
 199 .. clicmd:: babel resend-delay (20-655340)
 200
 201    Specifies the time in milliseconds after which an 'important' request or
 202    update will be resent.  The default is 2000 ms.  You probably don't want to
 203    tweak this value.
 204
 205 .. index:: babel smoothing-half-life (0-65534)
 206
 207 .. clicmd:: babel smoothing-half-life (0-65534)
 208
 209    Specifies the time constant, in seconds, of the smoothing algorithm used for
 210    implementing hysteresis.  Larger values reduce route oscillation at the cost
 211    of very slightly increasing convergence time.  The value 0 disables
 212    hysteresis, and is suitable for wired networks.  The default is 4 s.
 213
 214 .. _babel-redistribution:
 215
 216 Babel redistribution
 217 ====================
 218
 219 .. index::
 220    single: redistribute <ipv4|ipv6> KIND
 221    single: no redistribute <ipv4|ipv6> KIND
 222
 223 .. clicmd:: [no] redistribute <ipv4|ipv6> KIND
 224
 225    Specify which kind of routes should be redistributed into Babel.
 226
 227 .. _show-babel-information:
 228
 229 Show Babel information
 230 ======================
 231
 232 These commands dump various parts of *babeld*'s internal state.
 233
 234 .. index:: show babel route
 235
 236 .. clicmd:: show babel route
 237
 238 .. index:: show babel route A.B.C.D
 239
 240 .. clicmd:: show babel route A.B.C.D
 241
 242 .. index:: show babel route X:X::X:X
 243
 244 .. clicmd:: show babel route X:X::X:X
 245
 246 .. index:: show babel route A.B.C.D/M
 247
 248 .. clicmd:: show babel route A.B.C.D/M
 249
 250 .. index:: show babel route X:X::X:X/M
 251
 252 .. clicmd:: show babel route X:X::X:X/M
 253
 254 .. index:: show babel interface
 255
 256 .. clicmd:: show babel interface
 257
 258 .. index:: show babel interface IFNAME
 259
 260 .. clicmd:: show babel interface IFNAME
 261
 262 .. index:: show babel neighbor
 263
 264 .. clicmd:: show babel neighbor
 265
 266 .. index:: show babel parameters
 267
 268 .. clicmd:: show babel parameters
 269
 270 Babel debugging commands
 271 ========================
 272
 273 .. index::
 274    simple: debug babel KIND
 275    simple: no debug babel KIND
 276
 277 .. clicmd:: [no] debug babel KIND
 278
 279    Enable or disable debugging messages of a given kind. ``KIND`` can
 280    be one of:
 281
 282    - ``common``
 283    - ``filter``
 284    - ``timeout``
 285    - ``interface``
 286    - ``route``
 287    - ``all``
 288
 289 .. note::
 290    If you have compiled with the ``NO_DEBUG`` flag, then these commands aren't
 291    available.