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

@section Capability Negotiation

  When adding IPv6 routing information exchange feature to BGP.  There
were some proposals.  @acronym{IETF} @acronym{IDR} working group finally
take a proposal called Multiprotocol Extension for BGP.  The
specification is described in RFC2283.  The protocol does not define new
protocols.  It defines new attributes to existing BGP.  When it is used
exchanging IPv6 routing information it is called BGP-4+.  When it is
used for exchanging multicast routing information it is called MBGP.

  @command{bgpd} supports Multiprotocol Extension for BGP.  So if remote peer
supports the protocol, @command{bgpd} can exchange IPv6 and/or multicast routing
information.

  Traditional BGP does not have the feature to detect remote peer's
capability whether it can handle other than IPv4 unicast routes.  This
is a big problem using Multiprotocol Extension for BGP to operational
network.  @cite{draft-ietf-idr-bgp4-cap-neg-04.txt} is proposing a
feature called Capability Negotiation.  @command{bgpd} use this Capability
Negotiation to detect remote peer's capabilities.  If the peer is only
configured as IPv4 unicast neighbor, @command{bgpd} does not send these Capability
Negotiation packets.

  By default, Zebra will bring up peering with minimal common capability
for the both sides.  For example, local router has unicast and multicast 
capabilitie and remote router has unicast capability.  In this case,
the local router will establish the connection with unicast only capability.
When there are no common capabilities, Zebra sends Unsupported Capability
error and then resets the connection.

  If you want to completely match capabilities with remote peer.  Please
use @command{strict-capability-match} command.
  
@deffn {BGP} {neighbor @var{peer} strict-capability-match} {}
@deffnx {BGP} {no neighbor @var{peer} strict-capability-match} {}
Strictly compares remote capabilities and local capabilities.  If capabilities
are different, send Unsupported Capability error then reset connection.
@end deffn

  You may want to disable sending Capability Negotiation OPEN message
optional parameter to the peer when remote peer does not implement
Capability Negotiation.  Please use @command{dont-capability-negotiate}
command to disable the feature.

@deffn {BGP} {neighbor @var{peer} dont-capability-negotiate} {}
@deffnx {BGP} {no neighbor @var{peer} dont-capability-negotiate} {}
Suppress sending Capability Negotiation as OPEN message optional
parameter to the peer.  This command only affects the peer is configured
other than IPv4 unicast configuration.
@end deffn

  When remote peer does not have capability negotiation feature, remote
peer will not send any capabilities at all.  In that case, bgp configures
the peer with configured capabilities.

  You may prefer locally configured capabilities more than the negotiated
capabilities even though remote peer sends capabilities.  If the peer is
configured by @command{override-capability}, @command{bgpd} ignores received
capabilities then override negotiated capabilities with configured values.

@deffn {BGP} {neighbor @var{peer} override-capability} {}
@deffnx {BGP} {no neighbor @var{peer} override-capability} {}
Override the result of Capability Negotiation with local configuration.
Ignore remote peer's capability value.
@end deffn

@node Route Reflector, Route Server, Capability Negotiation, BGP
@comment  node-name,  next,  previous,  up
@section Route Reflector

@deffn {BGP} {bgp cluster-id @var{a.b.c.d}} {}
@end deffn

@deffn {BGP} {neighbor @var{peer} route-reflector-client} {}
@deffnx {BGP} {no neighbor @var{peer} route-reflector-client} {}
@end deffn

@node Route Server, How to set up a 6-Bone connection, Route Reflector, BGP
@comment  node-name,  next,  previous,  up
@section Route Server

At an Internet Exchange point, many ISPs are connected to each other by
external BGP peering.  Normally these external BGP connection are done by
@code{full mesh} method.  As with internal BGP full mesh formation,
this method has a scaling problem.

This scaling problem is well known.  Route Server is a method to resolve
the problem.  Each ISP's BGP router only peers to Route Server.  Route
Server serves as BGP information exchange to other BGP routers.  By
applying this method, numbers of BGP connections is reduced from
O(n*(n-1)/2) to O(n).

Unlike normal BGP router, Route Server must have several routing tables
for managing different routing policies for each BGP speaker.  We call the
routing tables as different @code{view}s.  @command{bgpd} can work as
normal BGP router or Route Server or both at the same time.

@menu
* Multiple instance::           
* BGP instance and view::       
* Routing policy::              
* Viewing the view::            
@end menu

@node Multiple instance, BGP instance and view, Route Server, Route Server
@comment  node-name,  next,  previous,  up
@subsection Multiple instance

To enable multiple view function of @code{bgpd}, you must turn on
multiple instance feature beforehand.

@deffn {Command} {bgp multiple-instance} {}
Enable BGP multiple instance feature.  After this feature is enabled,
you can make multiple BGP instances or multiple BGP views.
@end deffn

@deffn {Command} {no bgp multiple-instance} {}
Disable BGP multiple instance feature.  You can not disable this feature
when BGP multiple instances or views exist.
@end deffn

When you want to make configuration more Cisco like one, 

@deffn {Command} {bgp config-type cisco} {}
Cisco compatible BGP configuration output.
@end deffn

When bgp config-type cisco is specified, 

``no synchronization'' is displayed.
``no auto-summary'' is desplayed.

``network'' and ``aggregate-address'' argument is displayed as
``A.B.C.D M.M.M.M''

Zebra: network 10.0.0.0/8
Cisco: network 10.0.0.0

Zebra: aggregate-address 192.168.0.0/24
Cisco: aggregate-address 192.168.0.0 255.255.255.0

Community attribute handling is also different.  If there is no
configuration is specified community attribute and extended community
attribute are sent to neighbor.  When user manually disable the
feature community attribute is not sent to the neighbor.  In case of
``bgp config-type cisco'' is specified, community attribute is not
sent to the neighbor by default.  To send community attribute user has
to specify ``neighbor A.B.C.D send-community'' command.

!
router bgp 1
 neighbor 10.0.0.1 remote-as 1
 no neighbor 10.0.0.1 send-community
!

!
router bgp 1
 neighbor 10.0.0.1 remote-as 1
 neighbor 10.0.0.1 send-community
!

@deffn {Command} {bgp config-type zebra} {}
Zebra style BGP configuration.  This is default.
@end deffn

@node BGP instance and view, Routing policy, Multiple instance, Route Server
@comment  node-name,  next,  previous,  up
@subsection BGP instance and view

BGP instance is a normal BGP process.  The result of route selection
goes to the kernel routing table.  You can setup different AS at the
same time when BGP multiple instance feature is enabled.

@deffn {Command} {router bgp @var{as-number}} {}
Make a new BGP instance.  You can use arbitrary word for the @var{name}.
@end deffn

@example
@group
bgp multiple-instance
!
router bgp 1
 neighbor 10.0.0.1 remote-as 2
 neighbor 10.0.0.2 remote-as 3
!
router bgp 2
 neighbor 10.0.0.3 remote-as 4
 neighbor 10.0.0.4 remote-as 5
@end group
@end example

BGP view is almost same as normal BGP process. The result of
route selection does not go to the kernel routing table.  BGP view is
only for exchanging BGP routing information.

@deffn {Command} {router bgp @var{as-number} view @var{name}} {}
Make a new BGP view.  You can use arbitrary word for the @var{name}.  This
view's route selection result does not go to the kernel routing table.
@end deffn

With this command, you can setup Route Server like below.

@example
@group
bgp multiple-instance
!
router bgp 1 view 1
 neighbor 10.0.0.1 remote-as 2
 neighbor 10.0.0.2 remote-as 3
!
router bgp 2 view 2
 neighbor 10.0.0.3 remote-as 4
 neighbor 10.0.0.4 remote-as 5
@end group
@end example

@node Routing policy, Viewing the view, BGP instance and view, Route Server
@comment  node-name,  next,  previous,  up
@subsection Routing policy

You can set different routing policy for a peer.  For example, you can
set different filter for a peer.

@example
@group
bgp multiple-instance
!
router bgp 1 view 1
 neighbor 10.0.0.1 remote-as 2
 neighbor 10.0.0.1 distribute-list 1 in
!
router bgp 1 view 2
 neighbor 10.0.0.1 remote-as 2
 neighbor 10.0.0.1 distribute-list 2 in
@end group
@end example

This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view
2.  When the update is inserted into view 1, distribute-list 1 is
applied.  On the other hand, when the update is inserted into view 2,
distribute-list 2 is applied.

@node Viewing the view,  , Routing policy, Route Server
@comment  node-name,  next,  previous,  up
@subsection Viewing the view

To display routing table of BGP view, you must specify view name.

@deffn {Command} {show ip bgp view @var{name}} {}
Display routing table of BGP view @var{name}.
@end deffn

@node How to set up a 6-Bone connection, Dump BGP packets and table, Route Server, BGP
@comment  node-name,  next,  previous,  up
@section How to set up a 6-Bone connection

@example
@group
zebra configuration 
=================== 
!  
! Actually there is no need to configure zebra 
!

bgpd configuration
==================
!
! This means that routes go through zebra and into the kernel.
!
router zebra
!
! MP-BGP configuration
!
router bgp 7675
 bgp router-id 10.0.0.1
 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as @var{as-number}
!
 address-family ipv6
 network 3ffe:506::/32
 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as @var{as-number}
 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
 exit-address-family
!
ipv6 access-list all permit any
!
! Set output nexthop address.
!
route-map set-nexthop permit 10
 match ipv6 address all
 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
!
! logfile FILENAME is obsolete.  Please use log file FILENAME
!
log file bgpd.log
!
@end group
@end example

@node Dump BGP packets and table,  , How to set up a 6-Bone connection, BGP
@comment  node-name,  next,  previous,  up
@section Dump BGP packets and table

@deffn Command {dump bgp all @var{path}} {}
@deffnx Command {dump bgp all @var{path} @var{interval}} {}
Dump all BGP packet and events to @var{path} file.
@end deffn 

@deffn Command {dump bgp updates @var{path}} {}
@deffnx Command {dump bgp updates @var{path} @var{interval}} {}
Dump BGP updates to @var{path} file.
@end deffn

@deffn Command {dump bgp routes @var{path}} {}
@deffnx Command {dump bgp routes @var{path}} {}
Dump whole BGP routing table to @var{path}.  This is heavy process.
@end deffn