ospfd(8) - OpenBSD manual pages

ospfd(8) - OpenBSD manual pages
OSPFD(8)
System
Manager's Manual
OSPFD(8)
NAME
ospfd
Open Shortest Path First (OSPF) routing
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. It
has several advantages over RIP. For instance, every router has an
understanding of the complete network topology. Response to changes in the
network is faster. Furthermore, failure detection is improved.
The OSPF daemon maintains a Link State Database (LSDB) containing
information about routers and networks within an Autonomous System (AS).
Dijkstra's shortest path first algorithm is used to compute a
Routing Information Base (RIB) using the LSDB as input. The Forwarding
Information Base (FIB), a.k.a. the kernel routing table, is updated with
information from the RIB.
OSPF routers discover one another automatically via OSPF hello
packets. OSPF routers communicate via two multicast groups: 224.0.0.5 (all
Shortest Path First routers) and 224.0.0.6 (all Designated Routers). OSPF
runs directly on top of IP and uses neither TCP nor UDP. IP protocol number
89 is reserved for OSPF.
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.
In a multi-access network such as Ethernet, it is unfeasible for
all routers to synchronize their LSDB with all other routers in the network.
In such networks a Designated Router (DR) and a Backup Designated Router
(BDR) are 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. Routers with FULL adjacency
exchange information about their LSDBs. A router not elected either DR or
BDR will have 2-WAY adjacency with all routers but the DR and BDR. Routers
with 2-WAY adjacency recognize that they know each other, but do not
exchange information about their LSDBs. If a DR or BDR fails, another router
is elected DR or BDR and all routers form FULL adjacencies with the newly
elected DR or BDR.
When routers are connected via point-to-point links, DR and BDR
election is skipped since only two routers are connected to the link.
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.
AS Border Routers (ASBR) are connected to an OSPF network and
other external networks via BGP, RIP, or static routing, and provide
connectivity to networks outside the AS.
To have
ospfd
enabled at boot time, use
“rcctl enable ospfd”, which sets
ospfd_flags=""
in
rc.conf.local(8)
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)
STANDARDS
J. Moy
OSPF Version 2
RFC
2328
April 1998
A. Retana
L. Nguyen
R. White
A. Zinin
, and
D.
McPherson
OSPF Stub Router Advertisement
RFC
3137
June 2001
HISTORY
The
ospfd
program first appeared in
OpenBSD 3.7
BUGS
Virtual links are currently not available in
ospfd
OpenBSD-current
March 2, 2023
OSPFD(8)