Overview

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 flag, 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 netstsat utility. Almost of these commands work only the user has root privilege. Zebra has different system administration method. There are two user mode 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.

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 a 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 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 daemon on the same machine. This architecture creates new possibilities for the routing system.

bgpd	ripd	ospfd	zebra
Unix Kernel routing table

Zebra System Architecture

Multi process architecture bring us extensibility, modularity and maintainability. At the same time it also bring us many configuration files and terminal interface. Each daemon has it's own configuration file and terminal interface. When you configure static route, it must be done in zebra configuration file. When you configure BGP network it must be done in bgpd configuration file. It is very annoying thing. To resolve the problem, Zebra provides integrated user interface shell called vsh. vsh connect to each daemon with UNIX domain socket then work as proxy of user input.

Zebra was planned to use multi-threaded mechanism when it runs with a kernel that supports multi-threads. But at this moment, the thread library which comes with GNU/Linux or FreeBSD has some problems for running reliable services such as routing software, so we dont use threads at all, instead we use the select(2) system call for multiplexing the events.

• 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 stack. For BSD, we recommend KAME IPv6 stack. Solaris IPv6 stack is not yet supported.

• Linux IPv6 stack for GNU/Linux 2.2.x and upper.
• Kame IPv6 stack for BSD
• INRIA IPv6 stack for BSD

Supported RFCs

Below is the list of currently supported routing protocol RFCs:

• RFC1058
  Routing Information Protocol. C.L. Hedrick. Jun-01-1998
• RFC1771
  A Border Gateway Protocol 4 (BGP-4.) Y. Rekhter & T. Li. March 1995.
• RFC1997
  BGP Communities Attribute. R. Chandra, P. Traina & T. Li. August 1996.
• RFC2080
  RIPng for IPv6. G. Malkin, R. Minnear. January 1997.
• RFC2283
  Multiprotocol Extensions for BGP-4. T. Bates, R. Chandra, D. Katz, Y. Rekhter. February 1998.
• RFC2328
  OSPF Version 2. J. Moy. April 1998.
• RFC2453
  RIP Version 2. G. Malkin. November 1998.
• RFC2545
  Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing. P. Marques, F. Dupont. March 1999.
• RFC2740
  OSPF for IPv6. R. Coltun, D. Perguson, J.Moy. December 1999.
• RFC2796
  BGP Route Reflection An alternative to full mesh IBGP T. Bates R. Chandrasekeran. June 1996.
• When SNMP support is enabled, below RFC is also supported
• RFC1227
  SNMP MUX protocol and MIB. M.T. Rose. May-01-1991.
• RFC 1657
  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.
• RFC1850
  OSPF Version 2 Management Information Base. F. Baker, R. Coltun. November 1995.

How to get Zebra

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

Bug Reports