bgpd.texi

大名鼎鼎的路由器源码。程序分ZEBRA、OSPFRIP等3个包。程序框架采用一个路由协议一个进程的方式

@deffn {BGP} {neighbor @var{peer} route-map @var{name} [in|out]} {}
Apply a route-map on the neighbor.  @var{direct} must be @code{in} or
@code{out}.
@end deffn

@c -----------------------------------------------------------------------
@node BGP Peer Group, BGP Address Family, BGP Peer, BGP
@comment  node-name,  next,  previous,  up
@section BGP Peer Group

@deffn {BGP} {neighbor @var{word} peer-group} {}
This command defines a new peer group.
@end deffn

@deffn {BGP} {neighbor @var{peer} peer-group @var{word}} {}
This command bind specific peer to peer group @var{word}.
@end deffn

@node BGP Address Family, Autonomous System, BGP Peer Group, BGP
@comment  node-name,  next,  previous,  up
@section BGP Address Family



@page
@c -----------------------------------------------------------------------
@node Autonomous System, BGP Communities Attribute, BGP Address Family, BGP
@comment  node-name,  next,  previous,  up
@section Autonomous System

  AS (Autonomous System) is one of the essential element of BGP.  BGP
is a distance vector routing protocol.  AS framework provides distance
vector metric and loop detection to BGP.  @code{RFC1930} -
@cite{Guidelines for creation, selection, and registration of an
Autonomous System (AS)} describes how to use AS.

  AS number is tow octet digita value.  So the value range is from 1
to 65535.  AS numbers 64512 through 65535 are defined as private AS
numbers.  Private AS numbers must not to be advertised in the global
Internet.

@menu
* AS Path Regular Expression::  
* Display BGP Routes by AS Path::  
* AS Path Access List::         
* Using AS Path in Route Map::  
* Private AS Numbers::          
@end menu

@node AS Path Regular Expression, Display BGP Routes by AS Path, Autonomous System, Autonomous System
@comment  node-name,  next,  previous,  up
@subsection AS Path Regular Expression

  AS path regular expression can be used for displaying BGP routes and
AS path access list.  AS path regular expression is based on
@code{POSIX 1003.2} regular expressions.  Following description is
just a subset of @code{POSIX} regular expression.  User can use full
@code{POSIX} regular expression.  Adding to that special character '_'
is added for AS path regular expression.

@table @code
@item .
Matches any single character.
@item *
Matches 0 or more occurrences of pattern.
@item +
Matches 1 or more occurrences of pattern.
@item ?
Match 0 or 1 occurrences of pattern.
@item ^
Matches the beginning of the line.
@item $
Matches the end of the line.
@item _
Character @code{_} has special meanings in AS path regular expression.
It matches to space and comma , and AS set delimiter @{ and @} and AS
confederation delimiter @code{(} and @code{)}.  And it also matches to
the beginning of the line and the end of the line.  So @code{_} can be
used for AS value boundaries match.  @code{show ip bgp regexp _7675_}
matches to all of BGP routes which as AS number include @var{7675}.
@end table

@node Display BGP Routes by AS Path, AS Path Access List, AS Path Regular Expression, Autonomous System
@comment  node-name,  next,  previous,  up
@subsection Display BGP Routes by AS Path

  To show BGP routes which has specific AS path information @code{show
ip bgp} command can be used.  

@deffn Command {show ip bgp regexp @var{line}} {}
This commands display BGP routes that matches AS path regular
expression @var{line}.
@end deffn

@node AS Path Access List, Using AS Path in Route Map, Display BGP Routes by AS Path, Autonomous System
@comment  node-name,  next,  previous,  up
@subsection AS Path Access List

  AS path access list is user defined AS path.

@deffn {Command} {ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
This command defines a new AS path access list.
@end deffn

@deffn {Command} {no ip as-path access-list @var{word}} {}
@deffnx {Command} {no ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
@end deffn

@node Using AS Path in Route Map, Private AS Numbers, AS Path Access List, Autonomous System
@comment  node-name,  next,  previous,  up
@subsection Using AS Path in Route Map

@deffn {Route Map} {match as-path @var{word}} {}
@end deffn

@deffn {Route Map} {set as-path prepend @var{as-path}} {}
@end deffn

@node Private AS Numbers,  , Using AS Path in Route Map, Autonomous System
@comment  node-name,  next,  previous,  up
@subsection Private AS Numbers

@page
@c -----------------------------------------------------------------------
@node BGP Communities Attribute, BGP Extended Communities Attribute, Autonomous System, BGP
@comment  node-name,  next,  previous,  up
@section BGP Communities Attribute

  BGP communities attribute is widely used for implementing policy
routing.  Network operators can manipulate BGP communities attribute
based on their network policy.  BGP communities attribute is defined
in @code{RFC1997} - @cite{BGP Communities Attribute} and
@code{RFC1998} - @cite{An Application of the BGP Community Attribute
in Multi-home Routing}.  It is an optional transitive attribute,
therefore local policy can travel through different autonomous system.

  Communities attribute is a set of communities values.  Each
communities value is 4 octet long.  The following format is used to
define communities value.

@table @code
@item AS:VAL
This format represents 4 octet communities value.  @code{AS} is high
order 2 octet in digit format.  @code{VAL} is low order 2 octet in
digit format.  This format is useful to define AS oriented policy
value.  For example, @code{7675:80} can be used when AS 7675 wants to
pass local policy value 80 to neighboring peer.
@item internet
@code{internet} represents well-known communities value 0.
@item no-export
@code{no-export} represents well-known communities value @code{NO_EXPORT}@*
@r{(0xFFFFFF01)}.  All routes carry this value must not be advertised
to outside a BGP confederation boundary.  If neighboring BGP peer is
part of BGP confederation, the peer is considered as inside a BGP
confederation boundary, so the route will be announced to the peer.
@item no-advertise
@code{no-advertise} represents well-known communities value
@code{NO_ADVERTISE}@*@r{(0xFFFFFF02)}.  All routes carry this value
must not be advertise to other BGP peers.
@item local-AS
@code{local-AS} represents well-known communities value
@code{NO_EXPORT_SUBCONFED} @r{(0xFFFFFF03)}.  All routes carry this
value must not be advertised to external BGP peers.  Even if the
neighboring router is part of confederation, it is considered as
external BGP peer, so the route will not be announced to the peer.
@end table

  When BGP communities attribute is received, duplicated communities
value in the communities attribute is ignored and each communities
values are sorted in numerical order.
  
@menu
* BGP Community Lists::         
* Numbered BGP Community Lists::  
* BGP Community in Route Map::  
* Display BGP Routes by Community::  
* Using BGP Communities Attribute::  
@end menu

@node BGP Community Lists, Numbered BGP Community Lists, BGP Communities Attribute, BGP Communities Attribute
@comment  node-name,  next,  previous,  up
@subsection BGP Community Lists

  BGP community list is a user defined BGP communites attribute list.
BGP community list can be used for matching or manipulating BGP
communities attribute in updates.

  There are two types of community list.  One is standard community
list and another is expanded community list.  Standard community list
defines communities attribute.  Expanded community list defines
communities attribute string with regular expression.  Standard
community list is compiled into binary format when user define it.
Standard community list will be directly compared to BGP communities
attribute in BGP updates.  Therefore the comparison is faster than
expanded community list.

@deffn Command {ip community-list standard @var{name} @{permit|deny@} @var{community}} {}
This command defines a new standard community list.  @var{community}
is communities value.  The @var{community} is compiled into community
structure.  We can define multiple community list under same name.  In
that case match will happen user defined order.  Once the
community list matches to communities attribute in BGP updates it
return permit or deny by the community list definition.  When there is
no matched entry, deny will be returned.  When @var{community} is
empty it matches to any routes.
@end deffn

@deffn Command {ip community-list expanded @var{name} @{permit|deny@} @var{line}} {}
This command defines a new expanded community list.  @var{line} is a
string expression of communities attribute.  @var{line} can include
regular expression to match communities attribute in BGP updates.
@end deffn

@deffn Command {no ip community-list @var{name}} {}
@deffnx Command {no ip community-list standard @var{name}} {}
@deffnx Command {no ip community-list expanded @var{name}} {}
These commands delete community lists specified by @var{name}.  All of
community lists shares a single name space.  So community lists can be
removed simpley specifying community lists name.
@end deffn

@deffn {Command} {show ip community-list} {}
@deffnx {Command} {show ip community-list @var{name}} {}
This command display current community list information.  When
@var{name} is specified the specified community list's information is
shown.

@example
# show ip community-list 
Named Community standard list CLIST
    permit 7675:80 7675:100 no-export
    deny internet
Named Community expanded list EXPAND
    permit :

# show ip community-list CLIST
Named Community standard list CLIST
    permit 7675:80 7675:100 no-export
    deny internet
@end example
@end deffn

@node Numbered BGP Community Lists, BGP Community in Route Map, BGP Community Lists, BGP Communities Attribute
@comment  node-name,  next,  previous,  up
@subsection Numbered BGP Community Lists

  When number is used for BGP community list name, the number has
special meanings.  Community list number in the range from 1 and 99 is
standard community list.  Community list number in the range from 100
to 199 is expanded community list.  These community lists are called
as numbered community lists.  On the other hand normal community lists
is called as named community lists.

@deffn Command {ip community-list <1-99> @{permit|deny@} @var{community}} {}
This command defines a new community list.  <1-99> is standard
community list number.  Community list name within this range defines
standard community list.  When @var{community} is empty it matches to
any routes.
@end deffn

@deffn Command {ip community-list <100-199> @{permit|deny@} @var{community}} {}
This command defines a new community list.  <100-199> is expanded
community list number.  Community list name within this range defines
expanded community list.
@end deffn

@deffn Command {ip community-list @var{name} @{permit|deny@} @var{community}} {}
When community list type is not specifed, the community list type is
automatically detected.  If @var{community} can be compiled into
communities attribute, the community list is defined as a standard
community list.  Otherwise it is defined as an expanded community
list.  This feature is left for backward compability.  Use of this
feature is not recommended.
@end deffn

@node BGP Community in Route Map, Display BGP Routes by Community, Numbered BGP Community Lists, BGP Communities Attribute
@comment  node-name,  next,  previous,  up
@subsection BGP Community in Route Map

  In Route Map (@pxref{Route Map}), we can match or set BGP
communities attribute.  Using this feature network operator can
implement their network policy based on BGP communities attribute.

  Following commands can be used in Route Map.

@deffn {Route Map} {match community @var{word}} {}
@deffnx {Route Map} {match community @var{word} exact-match} {}
This command perform match to BGP updates using community list
@var{word}.  When the one of BGP communities value match to the one of
communities value in community list, it is match.  When
@code{exact-match} keyword is spcified, match happen only when BGP
updates have completely same communities value specified in the
community list.
@end deffn

@deffn {Route Map} {set community none} {}
@deffnx {Route Map} {set community @var{community}} {}
@deffnx {Route Map} {set community @var{community} additive} {}
This command manipulate communities value in BGP updates.  When
@code{none} is specified as communities value, it removes entire
communities attribute from BGP updates.  When @var{community} is not
@code{none}, specified communities value is set to BGP updates.  If
BGP updates already has BGP communities value, the existing BGP
communities value is replaced with specified @var{community} value.
When @code{additive} keyword is specified, @var{community} is appended
to the existing communities value.
@end deffn

@deffn {Route Map} {set comm-list @var{word} delete} {}
This command remove communities value from BGP communities attribute.
The @var{word} is community list name.  When BGP route's communities
value matches to the community list @var{word}, the communities value
is removed.  When all of communities value is removed eventually, the
BGP update's communities attribute is completely removed.
@end deffn

@node Display BGP Routes by Community, Using BGP Communities Attribute, BGP Community in Route Map, BGP Communities Attribute
@comment  node-name,  next,  previous,  up
@subsection Display BGP Routes by Community

  To show BGP routes which has specific BGP communities attribute,
@code{show ip bgp} command can be used.  The @var{community} value and
community list can be used for @code{show ip bgp} command.