path: root/doc/routemap.texi

@node Route Map
@chapter Route Map

Route maps provide a means to both filter and/or apply actions to
route, hence allowing policy to be applied to routes.

@menu
* Route Map Command::           
* Route Map Match Command::     
* Route Map Set Command::
* Route Map Call Command::
* Route Map Exit Action Command::
* Route Map Examples::
@end menu

Route-maps are an ordered list of route-map entries. Each entry may
specify up to four distincts sets of clauses:

@table @samp
@item Matching Policy

This specifies the policy implied if the @samp{Matching Conditions} are
met or not met, and which actions of the route-map are to be taken, if
any. The two possibilities are:

@itemize @minus
@item
@samp{permit}: If the entry matches, then carry out the @samp{Set
Actions}. Then finish processing the route-map, permitting the route,
unless an @samp{Exit Action} indicates otherwise.

@item
@samp{deny}: If the entry matches, then finish processing the route-map and
deny the route (return @samp{deny}).
@end itemize

The @samp{Matching Policy} is specified as part of the command which
defines the ordered entry in the route-map. See below.

@item Matching Conditions

A route-map entry may, optionally, specify one or more conditions which
must be matched if the entry is to be considered further, as governed
by the Match Policy. If a route-map entry does not explicitely specify
any matching conditions, then it always matches.

@item Set Actions

A route-map entry may, optionally, specify one or more @samp{Set
Actions} to set or modify attributes of the route.

@item Call Action

Call to another route-map, after any @samp{Set Actions} have been
carried out. If the route-map called returns @samp{deny} then
processing of the route-map finishes and the route is denied,
regardless of the @samp{Matching Policy} or the @samp{Exit Policy}. If
the called route-map returns @samp{permit}, then @samp{Matching Policy}
and @samp{Exit Policy} govern further behaviour, as normal.

@item Exit Policy

An entry may, optionally, specify an alternative @samp{Exit Policy} to
take if the entry matched, rather than the normal policy of exiting the
route-map and permitting the route. The two possibilities are:

@itemize @minus 
@item
@samp{next}: Continue on with processing of the route-map entries.

@item
@samp{goto N}: Jump ahead to the first route-map entry whose order in
the route-map is >= N. Jumping to a previous entry is not permitted.
@end itemize
@end table

The default action of a route-map, if no entries match, is to deny.
I.e. a route-map essentially has as its last entry an empty @samp{deny}
entry, which matches all routes. To change this behaviour, one must
specify an empty @samp{permit} entry as the last entry in the route-map.

To summarise the above:

@multitable {permit} {action} {No Match}
@headitem           @tab Match  @tab No Match
@item @emph{Permit} @tab action @tab cont
@item @emph{Deny}   @tab deny   @tab cont
@end multitable

@table @samp

@item action
@itemize @minus
@item
Apply @emph{set} statements

@item
If @emph{call} is present, call given route-map. If that returns a @samp{deny}, finish
processing and return @samp{deny}.

@item
If @samp{Exit Policy} is @emph{next}, goto next route-map entry

@item
If @samp{Exit Policy} is @emph{goto}, goto first entry whose order in the list
is >= the given order.

@item
Finish processing the route-map and permit the route.
@end itemize

@item deny
@itemize @minus
@item
The route is denied by the route-map (return @samp{deny}).
@end itemize

@item cont
@itemize @minus
@item
goto next route-map entry
@end itemize
@end table

@node Route Map Command
@section Route Map Command

@deffn {Command} {route-map @var{route-map-name} (permit|deny) @var{order}} {}

Configure the @var{order}'th entry in @var{route-map-name} with
@samp{Match Policy} of either @emph{permit} or @emph{deny}.

@end deffn

@node Route Map Match Command
@section Route Map Match Command

@deffn {Route-map Command} {match ip address @var{access_list}} {}
Matches the specified @var{access_list}
@end deffn

@deffn {Route-map Command} {match ip next-hop @var{ipv4_addr}} {}
Matches the specified @var{ipv4_addr}.
@end deffn

@deffn {Route-map Command} {match aspath @var{as_path}} {}
Matches the specified @var{as_path}.
@end deffn

@deffn {Route-map Command} {match metric @var{metric}} {}
Matches the specified @var{metric}.
@end deffn

@deffn {Route-map Command} {match community @var{community_list}} {}
Matches the specified  @var{community_list}
@end deffn

@node Route Map Set Command
@section Route Map Set Command

@deffn {Route-map Command} {set ip next-hop @var{ipv4_address}} {}
Set the BGP nexthop address.
@end deffn

@deffn {Route-map Command} {set local-preference @var{local_pref}} {}
Set the BGP local preference.
@end deffn

@deffn {Route-map Command} {set weight @var{weight}} {}
Set the route's weight.
@end deffn

@deffn {Route-map Command} {set metric @var{metric}} {}
Set the BGP attribute MED.
@end deffn

@deffn {Route-map Command} {set as-path prepend @var{as_path}} {}
Set the BGP AS path to prepend.
@end deffn

@deffn {Route-map Command} {set community @var{community}} {}
Set the BGP community attribute.
@end deffn

@deffn {Route-map Command} {set ipv6 next-hop global @var{ipv6_address}} {}
Set the BGP-4+ global IPv6 nexthop address.
@end deffn

@deffn {Route-map Command} {set ipv6 next-hop local @var{ipv6_address}} {}
Set the BGP-4+ link local IPv6 nexthop address.
@end deffn

@node Route Map Call Command
@section Route Map Call Command

@deffn {Route-map Command} {call @var{name}} {}
Call route-map @var{name}. If it returns deny, deny the route and
finish processing the route-map.
@end deffn

@node Route Map Exit Action Command
@section Route Map Exit Action Command

@deffn {Route-map Command} {on-match next} {}
@deffnx {Route-map Command} {continue} {}
Proceed on to the next entry in the route-map.
@end deffn

@deffn {Route-map Command} {on-match goto @var{N}} {}
@deffnx {Route-map Command} {continue @var{N}} {}
Proceed processing the route-map at the first entry whose order is >= N
@end deffn

@node Route Map Examples
@section Route Map Examples

A simple example of a route-map:

@example
@group
route-map test permit 10
 match ip address 10
 set local-preference 200
@end group
@end example

This means that if a route matches ip access-list number 10 it's
local-preference value is set to 200.

See @ref{BGP Configuration Examples} for examples of more sophisticated
useage of route-maps, including of the @samp{call} action.