Overview
********

Zebra is a routing software package that provides TCP/IP based routing services with routing protocols support such as RIPv1, RIPv2, RIPng, OSPFv2, OSPFv3, BGP-4, and BGP-4+ (see Supported RFC).  Zebra also supports special BGP Route Reflector and Route Server behavior.  In addition to traditional IPv4 routing protocols, Zebra also supports IPv6 routing protocols.  With SNMP daemon which supports SMUX protocol, Zebra provides routing protocol MIBs (see SNMP Support).

Zebra uses an advanced software architecture to provide you with a high quality, multi server routing engine.  Zebra has an interactive user interface for each routing protocol and supports common client commands.  Due to this design, you can add new protocol daemons to Zebra easily.  You can use Zebra library as your program's client user interface.

Zebra is an official GNU software and distributed under the GNU General Public License.

About Zebra
===========

Today, TCP/IP networks are covering all of the world.  The Internet has been deployed in many countries, companies, and to the home.  When you connect to the Internet your packet will pass many routers which have TCP/IP routing functionality.

A system with Zebra installed acts as a dedicated router.  With Zebra, your machine exchanges routing information with other routers using routing protocols.  Zebra uses this information to update the kernel routing table so that the right data goes to the right place.  You can dynamically change the configuration and you may view routing table information from the Zebra terminal interface.

Adding to routing protocol support, Zebra can setup interface's flags, interface's address, static routes and so on.  If you have a small network, or a stub network, or xDSL connection, configuring the Zebra routing software is very easy.  The only thing you have to do is to set up the interfaces and put a few commands about static routes and/or default routes.  If the network is rather large, or if the network structure changes frequently, you will want to take advantage of Zebra's dynamic routing protocol support for protocols such as RIP, OSPF or BGP. Zebra is with you.

Traditionally, UNIX based router configuration is done by ifconfig and route commands.  Status of routing table is displayed by netstat utility.  Almost of these commands work only if the user has root privileges.  Zebra has a different system administration method.  There are two user modes in Zebra.  One is normal mode, the other is enable mode.  Normal mode user can only view system status, enable mode user can change system configuration.  This UNIX account independent feature will be great help to the router administrator.

Currently, Zebra supports common unicast routing protocols.  Multicast routing protocols such as BGMP, PIM-SM, PIM-DM will be supported in Zebra 2.0.  MPLS support is going on.  In the future, TCP/IP filtering control, QoS control, diffserv configuration will be added to Zebra. Zebra project's final goal is making a productive, quality free TCP/IP routing software.

System Architecture
===================

Traditional routing software is made as a one process program which provides all of the routing protocol functionalities.  Zebra takes a different approach.  It is made from a collection of several daemons that work together to build the routing table.  There may be several protocol-specific routing daemons and zebra the kernel routing manager.

The ripd daemon handles the RIP protocol, while ospfd is a daemon which supports OSPF version 2. bgpd supports the BGP-4 protocol.  For changing the kernel routing table and for redistribution of routes between different routing protocols, there is a kernel routing table manager zebra daemon.  It is easy to add a new routing protocol daemons to the entire routing system without affecting any other software.  You need to run only the protocol daemon associated with routing protocols in use.  Thus, user may run a specific daemon and send routing reports to a central routing console.

There is no need for these daemons to be running on the same machine. You can even run several same protocol daemons on the same machine.  This architecture creates new possibilities for the routing system.

     +----+  +----+  +-----+  +-----+
     |bgpd|  |ripd|  |ospfd|  |zebra|
     +----+  +----+  +-----+  +-----+
                                 |
     +---------------------------|--+
     |                           v  |
     |  UNIX Kernel  routing table  |
     |                              |
     +------------------------------+

         Zebra System Architecture

Multi-process architecture brings extensibility, modularity and maintainability.  At the same time it also brings many configuration files and terminal interfaces.  Each daemon has it's own configuration file and terminal interface.  When you configure a static route, it must be done in zebra configuration file.  When you configure BGP network it must be done in bgpd configuration file.  This can be a very annoying thing.  To resolve the problem, Zebra provides integrated user interface shell called vtysh.  vtysh connects to each daemon with UNIX domain socket and then works as a proxy for user input.

Zebra was planned to use multi-threaded mechanism when it runs with a kernel that supports multi-threads.  But at the moment, the thread library which comes with GNU/Linux or FreeBSD has some problems with running reliable services such as routing software, so we don't use threads at all.  Instead we use the select(2) system call for multiplexing the events.

When zebra runs under a GNU Hurd kernel it will act as a kernel routing table itself.  Under GNU Hurd, all TCP/IP services are provided by user processes called pfinet.  Zebra will provide all the routing selection mechanisms for the process.  This feature will be implemented when GNU Hurd becomes stable.

Supported Platforms
===================

Currently Zebra supports GNU/Linux, BSD and Solaris.  Below is a list of OS versions on which Zebra runs.  Porting Zebra to other platforms is not so too difficult.  Platform dependent codes exist only in zebra daemon.  Protocol daemons are platform independent. Please let us know when you find out Zebra runs on a platform which is not listed below.

  * GNU/Linux 2.0.37

  * GNU/Linux 2.2.x

  * GNU/Linux 2.3.x

  * FreeBSD 2.2.8

  * FreeBSD 3.x

  * FreeBSD 4.x

  * NetBSD 1.4

  * OpenBSD 2.5

  * Solaris 2.6

  * Solaris 7

Some IPv6 stacks are in development.  Zebra supports following IPv6 stacks.  For BSD, we recommend KAME IPv6 stack.  Solaris IPv6 stack is not yet supported.

  * Linux IPv6 stack for GNU/Linux 2.2.x and higher.

  * KAME IPv6 stack for BSD.

  * INRIA IPv6 stack for BSD.

Supported RFC
=============

Below is the list of currently supported RFC's.

RFC1058
     Routing Information Protocol. C.L. Hedrick. Jun-01-1988.

RF2082
     RIP-2 MD5 Authentication. F. Baker, R. Atkinson. January 1997.

RFC2453
     RIP Version 2. G. Malkin. November 1998.

RFC2080
     RIPng for IPv6. G. Malkin, R. Minnear. January 1997.

RFC2328
     OSPF Version 2. J. Moy. April 1998.

RFC2740
     OSPF for IPv6. R. Coltun, D. Ferguson, J. Moy. December 1999.

RFC1771
     A Border Gateway Protocol 4 (BGP-4). Y. Rekhter & T. Li. March 1995.

RFC1965
     Autonomous System Confederations for BGP. P. Traina. June 1996.

RFC1997
     BGP Communities Attribute. R. Chandra, P. Traina & T. Li. August 1996.

RFC2545
     Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing. P. Marques, F. Dupont. March 1999.

RFC2796
     BGP Route Reflection An alternative to full mesh IBGP. T. Bates & R. Chandrasekeran. June 1996.

RFC2858
     Multiprotocol Extensions for BGP-4. T. Bates, Y. Rekhter, R. Chandra, D. Katz. June 2000.

RFC2842
     Capabilities Advertisement with BGP-4. R. Chandra, J. Scudder. May 2000.

When SNMP support is enabled, below RFC is also supported.

RFC1227
     SNMP MUX protocol and MIB. M.T. Rose. May-01-1991.

RFC1657
     Definitions of Managed Objects for the Fourth Version of the Border Gateway Protocol (BGP-4) using SMIv2. S. Willis, J. Burruss, J. Chu, Editor. July 1994.

RFC1724
     RIP Version 2 MIB Extension. G. Malkin & F. Baker. November 1994.

RFC1850
     OSPF Version 2 Management Information Base. F. Baker, R. Coltun. November 1995.

How to get Zebra
================

Zebra is still beta software and there is no officially released version.  So currently Zebra is distributed from Zebra beta ftp site located at:

ftp://ftp.zebra.org/pub/zebra

Once Zebra is released you can get it from GNU FTP site and its mirror sites.  We are planning Zebra-1.0 as the first released version.

Zebra's official web page is located at:

http://www.gnu.org/software/zebra/zebra.html.

There is a Zebra beta tester web page at:

http://www.zebra.org/.

You can get the latest beta software information from this page.

Mailing List
============

There is a mailing list for discussions about Zebra.  If you have any comments or suggestions to Zebra, please send mail to zebra@zebra.org.  New snapshot announcements, improvement notes, and patches are sent to the list.

To subscribe to the Zebra mailing list, please send a mail to majordomo@zebra.org with a message body that includes only:

     subscribe zebra

To unsubscribe from the list, please send a mail to majordomo@zebra.org with a message body that includes only:

     unsubscribe zebra

Bug Reports
===========

If you think you have found a bug, please send a bug report to bug-zebra@gnu.org.  When you send a bug report, please be careful about the points below.

  * Please note what kind of OS you are using.  If you use the IPv6 stack please note that as well.

  * Please show us the results of netstat -rn and ifconfig -a. Information from zebra's VTY command show ip route will also be helpful.

  * Please send your configuration file with the report.  If you specify arguments to the configure script please note that too.

Bug reports are very important for us to improve the quality of Zebra. Zebra is still in the development stage, but please don't hesitate to send a bug report to bug-zebra@gnu.org.