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OSPFD(8) BSD System Manager’s Manual OSPFD(8)

NAME

ospfd — Open Shortest Path First daemon

SYNOPSIS

ospfd [−dnv] [

−D macro=value
] [−f file] [−s socket]

DESCRIPTION

ospfd is an Open Shortest Path First (OSPF) daemon which manages routing tables. This implementation supports OSPF version 2, thus it is only capable of maintaining IPv4 routing tables.

OSPF is an interior gateway protocol designed to supersede RIP. The OSPF daemon maintains a Link State Database (LSDB) consisting of routers and networks.

Dijkstra’s shortest path first algorithm is used to compute the Route Information Base using the LSDB as input. The Forwarding Information Base a.k.a. the kernel route table is updated with information from the RIB.

OSPF routers communicate via two multicast groups: 224.0.0.5 all Shortest Path First routers and 224.0.0.6 all Designated Routers. The IP protocol number 89 is reserved for OSPF, furthermore OSPF packets omit the use of TCP and UDP.

OSPF has several advantages over RIP. For example every router has a complete network topology. Response to changes in the network are faster. Furthermore fail detection is much improved.

All routers in an OSPF network spend most of their time keeping each others LSDBs in sync. All routers must have the same information in the LSDB at all times. Every time the LSDB is updated the RIB is updated; if needed the FIB is also updated.

OSPF aware routers discover each other via OSPF hello packets.

In a multiaccess network such as Ethernet it is unfeasible for all routers to synchronize with all other routers in the network. In such networks a Designated Router (DR) and a Backup Designated Router (BDR) is elected. The DR’s responsibility is to synchronize with all routers; the BDR will not do much until the DR fails. The first router in a network is automatically elected DR, the second router BDR. All routers have a FULL adjacency with the DR and the BDR. A router not elected either DR or BDR will have 2-WAY adjacency with all routers but the DR and BDR. Routers that form 2-WAY adjacency recognize that they know each other. In case a DR or BDR should fail another router is elected and all routers change state on the newly elected router and synchronize to it.

When routers are connected via point-to-point links, the DR and BDR election is skipped since only two routers are connected.

To limit the impact changes in the network have on the LSDB it is possible to segment an OSPF network into areas. Area 0.0.0.0 a.k.a. the backbone area must always be present. Routers can be configured as Area Border Router (ABR), being part of multiple areas. Every area must have direct access to the backbone area. ABRs not directly connected to the backbone area need to establish a virtual link to a router in the backbone area. Virtual links are currently not available in ospfd.

AS Border Routers (ASBR) are connected to an OSPF network and other external networks, BGP, RIP, or statically routed.

ospfd is usually started at boot time, and can be enabled by setting the following in /etc/rc.conf.local:

ospfd_flags=""

See rc(8) and rc.conf(8) for more information on the boot process and enabling daemons.

A running ospfd can be controlled with the ospfctl(8) utility.

The options are as follows:

−D macro=value

Define macro to be set to value on the command line. Overrides the definition of macro in the configuration file.

−d

Do not daemonize. If this option is specified, ospfd will run in the foreground and log to stderr.

−f file

Specify an alternative configuration file.

−n

Configtest mode. Only check the configuration file for validity.

−s socket

Use an alternate location for the default control socket.

−v

Produce more verbose output.

FILES
/etc/ospfd.conf

Default ospfd configuration file.

/var/run/ospfd.sock

Unix-domain socket used for communication with ospfctl(8).

SEE ALSO

ospfd.conf(5), ospfctl(8)

OSPF Version 2

,

RFC 2328 ,
April 1998 .

OSPF Stub Router Advertisement

,

RFC 3137 ,
June 2001 .

HISTORY

The ospfd program first appeared in OpenBSD 3.7.

BSD April 7, 2009 BSD