Configuring OSPF
This
chapter describes how to configure OSPF. For a complete description of the OSPF
commands in this chapter, refer to the “OSPF Commands” chapter of the Network
Protocols Command Reference, Part 1. To locate documentation of
other commands that appear in this chapter, use the command reference
master index or search online.
Open
shortest path first (OSPF) is an IGP developed by the OSPF working group of the
Internet Engineering Task Force (IETF). Designed expressly for IP networks,
OSPF supports IP subnetting and tagging of externally derived routing
information. OSPF also allows packet authentication and uses IP multicast when
sending/receiving packets.
We support RFC 1253, Open Shortest Path First
(OSPF) MIB, August 1991. The OSPF MIB defines an IP routing protocol that
provides management information related to OSPF and is supported by Cisco
routers.
For
protocol-independent features, see the chapter “Configuring IP Routing
Protocol-Independent Features” in this document.
Cisco’s OSPF
Implementation
Cisco’s
implementation conforms to the OSPF Version 2 specifications detailed in the
Internet RFC 1583. The list that follows outlines key features supported in
Cisco’s OSPF implementation:
•
Stub areas—Definition of stub areas is supported.
•
Route redistribution—Routes learned via any IP
routing protocol can be redistributed into any other IP routing protocol. At
the intradomain level, this means that OSPF can import routes learned via IGRP,
RIP, and IS-IS. OSPF routes can also be exported into IGRP, RIP, and IS-IS. At
the interdomain level, OSPF can import routes learned via EGP and BGP. OSPF
routes can be exported into EGP and BGP.
•
Authentication—Plain text and MD5 authentication
among neighboring routers within an area is supported.
•
Routing interface parameters—Configurable
parameters supported include interface output cost, retransmission interval,
interface transmit delay, router priority, router “dead” and hello intervals,
and authentication key.
•
Virtual links—Virtual links are supported.
•
NSSA areas—RFC 1587.
•
OSPF over demand circuit—RFC 1793.
OSPF Configuration
Task List
Note To take
advantage of the OSPF stub area support, default
routing must be used in the stub area.
OSPF Configuration
Task List
OSPF
typically requires coordination among many internal routers, area border
routers (routers connected to multiple areas), and autonomous system
boundary routers. At a minimum, OSPF-based routers or access servers can be
configured with all default parameter values, no authentication, and interfaces
assigned to areas. If you intend to customize your environment, you must ensure
coordinated configurations of all routers.
To configure OSPF,
complete the tasks in the following sections. Enabling OSPF is mandatory; the
other tasks are optional, but might be required for your application.
In addition, you can specify route redistribution; see the
task “Redistribute Routing Information” in the chapter “Configuring IP Routing
Protocol-Independent Features” for information on how to configure route
redistribution.
Enable OSPF
Enable OSPF
As with
other routing protocols, enabling OSPF requires that you create an OSPF routing
process, specify the range of IP addresses to be associated with the routing
process, and assign area IDs to be associated with that range of IP addresses.
Perform the following tasks, starting in global configuration mode:
Task
|
Command
|
|
Step 1
|
Enable OSPF routing,
which places you
|
router ospf process-id
|
in router configuration
mode.
|
||
Step 2
|
Define an interface on
which OSPF runs
|
network address wildcard-mask area area-id
|
and define the area ID
for that interface.
|
||
Configure OSPF
Interface Parameters
Our OSPF
implementation allows you to alter certain interface-specific OSPF parameters,
as needed. You are not required to alter any of these parameters, but some
interface parameters must be consistent across all routers in an attached
network. Those parameters are controlled by the ip ospf hello-interval,
ip ospf dead-interval, and ip ospf authentication-key. commands.
Therefore, be sure that if you do configure any of these parameters, the
configurations for all routers on your network have compatible values.
In
interface configuration mode, specify any of the following interface parameters
as needed for your network:
Task
|
Command
|
Explicitly specify the
cost of sending a packet on
|
ip ospf cost cost
|
an OSPF interface.
|
|
Specify the number of
seconds between link state
|
ip ospf
retransmit-interval seconds
|
advertisement
retransmissions for adjacencies
|
|
belonging to an OSPF
interface.
|
|
Set the estimated number
of seconds it takes to
|
ip ospf transmit-delay seconds
|
transmit a link state
update packet on an OSPF
|
|
interface.
|
|
Set priority to help
determine the OSPF
|
ip ospf priority number
|
designated router for a
network.
|
|
Specify the length of
time, in seconds, between
|
ip ospf hello-interval seconds
|
the hello packets that
the Cisco IOS software
|
|
sends on an OSPF
interface.
|
|
Set the number of seconds
that a device’s hello
|
ip ospf dead-interval seconds
|
packets must not have
been seen before its
|
|
neighbors declare the
OSPF router down.
|
|
Assign a specific
password to be used by
|
ip ospf
authentication-key key
|
neighboring OSPF routers
on a network segment
|
|
that is using OSPF’s
simple password
|
|
authentication.
|
|
Enable
OSPF MD5 authentication.
|
ip ospf
message-digest-key keyid md5 key
|
Configure OSPF over
Different Physical Networks
Configure OSPF over
Different Physical Networks
OSPF classifies different media
into the following three types of networks by default:
•
Broadcast
networks (Ethernet, Token Ring, FDDI)
•
Nonbroadcast multiaccess networks (SMDS, Frame
Relay, X.25)
•
Point-to-point networks (HDLC, PPP)
You can configure your network as
either a broadcast or a nonbroadcast multiaccess network.
X.25 and
Frame Relay provide an optional broadcast capability that can be configured in
the map to allow OSPF to run as a broadcast network. See the x25 map and
frame-relay map command descriptions in the Wide-Area Networking
Command Reference for more detail.
Configure
Your OSPF Network Type
You have
the choice of configuring your OSPF network type as either broadcast or
nonbroadcast multiaccess, regardless of the default media type. Using this
feature, you can configure broadcast networks as nonbroadcast multiaccess
networks when, for example, you have routers in your network that do not
support multicast addressing. You also can configure nonbroadcast multiaccess
networks (such as X.25, Frame Relay, and SMDS) as broadcast networks. This
feature saves you from having to configure neighbors, as described in the section
“Configure OSPF for Nonbroadcast
Networks.”
Configuring
nonbroadcast, multiaccess networks as either broadcast or nonbroadcast assumes
that there are virtual circuits from every router to every router or fully
meshed network. This is not true for some cases, for example, because of cost
constraints, or when you have only a partially meshed network. In these cases,
you can configure the OSPF network type as a point-to-multipoint network.
Routing between two routers not directly connected will go through the router
that has virtual circuits to both routers. Note that you must not configure
neighbors when using this feature.
An OSPF
point-to-multipoint interface is defined as a numbered point-to-point interface
having one or more neighbors. It creates multiple host routes. An OSPF
point-to-multipoint network has the following benefits compared to nonbroadcast
multiaccess and point-to-point networks:
•
Point-to-multipoint is easier to configure because
it requires no configuration of neighbor commands, it consumes only one IP
subnet, and it requires no designated router election.
•
It
costs less because it does not require a fully meshed topology.
•
It is more reliable because it maintains
connectivity in the event of virtual circuit failure.
To configure your OSPF network type, perform
the following task in interface configuration mode:
Task
|
Command
|
Configure the OSPF
network type for a specified
|
ip ospf network {broadcast |
non-broadcast |
|
interface.
|
point-to-multipoint}
|
See the “OSPF Point-to-Multipoint Example”
section at the end of this chapter for an example of an OSPF
point-to-multipoint network.
Configure
OSPF for Nonbroadcast Networks
Because
there might be many routers attached to an OSPF network, a designated router
is selected for the network. It is necessary to use special configuration
parameters in the designated router selection if broadcast capability is not
configured.
Configure OSPF Area Parameters
These parameters need only be
configured in those devices that are themselves eligible to become the
designated router or backup designated router (in other words, routers or
access servers with a nonzero router priority value).
To
configure routers that interconnect to nonbroadcast networks, perform the
following task in router configuration mode:
Task
|
Command
|
Configure
routers or access servers
|
neighbor ip-address [priority number]
[poll-interval
|
interconnecting
to nonbroadcast networks.
|
seconds]
|
You can specify the following
neighbor parameters, as required:
•
Priority
for a neighboring router
•
Nonbroadcast poll interval
•
Interface through which the neighbor is reachable
Configure OSPF Area
Parameters
Our OSPF
software allows you to configure several area parameters. These area
parameters, shown in the following table, include authentication, defining stub
areas, and assigning specific costs to the default summary route. Authentication
allows password-based protection against unauthorized access to an area.
Stub
areas are areas into which information on external routes is not
sent. Instead, there is a default external route generated by the area
border router, into the stub area for destinations outside the autonomous
system. To further reduce the number of link state advertisements sent into a
stub area, you can configure no-summary on the ABR to prevent it from
sending summary link advertisement (link state advertisements Type 3) into the
stub area.
In router
configuration mode, specify any of the following area parameters as needed for
your network:
Task
|
Command
|
Enable authentication for
an OSPF area.
|
area area-id authentication
|
Enable MD5 authentication
for an OSPF area.
|
area area-id authentication
message-digest
|
Define an area to be a
stub area.
|
area area-id stub [no-summary]
|
Assign a specific cost to
the default summary
|
area area-id default-cost cost
|
route used for the stub
area.
|
|
Configure OSPF Not So
Stubby Area (NSSA)
NSSA area
is similar to OSPF stub area. NSSA does not flood Type 5 external link state
advertisements (LSAs) from the core into the area, but it has the ability of
importing AS external routes in a limited fashion within the area.
NSSA
allows importing of Type 7 AS external routes within NSSA area by
redistribution. These Type 7 LSAs are translated into Type 5 LSAs by NSSA ABR
which are flooded throughout the whole routing domain. Summarization and
filtering are supported during the translation.
Use NSSA
to simplify administration if you are an Internet service provider (ISP), or a
network administrator that must connect a central site using OSPF to a remote
site that is using a different routing protocol.
Configure Route
Summarization between OSPF Areas
Prior to NSSA, the connection between the corporate
site border router and the remote router could not be run as OSPF stub area
because routes for the remote site cannot be redistributed into stub area. A
simple protocol like RIP is usually run and handle the redistribution. This
meant maintaining two routing protocols. With NSSA, you can extend OSPF to
cover the remote connection by defining the area between the corporate router
and the remote router as an NSSA.
In router
configuration mode, specify the following area parameters as needed to configure
OSPF NSSA:
Task
|
Command
|
Define
an area to be NSSA.
|
area area-id nssa [no-redistribution]
|
[default-information-originate]
|
|
In router
configuration mode on the ABR, specify the following command to control
summarization and filtering of Type 7 LSA into Type 5 LSA:
Task
|
Command
|
(Optional) Control the
summarization and
|
summary address prefix mask [not advertise] [tag
tag]
|
filtering during the
translation.
|
|
Implementation
Considerations
Evaluate the following
considerations before implementing this feature:
•
You can set a Type 7 default route that can be
used to reach external destinations. When configured, the router generates a
Type 7 default into the NSSA by the NSSA ABR.
•
Every router within the same area must agree that
the area is NSSA; otherwise, the routers will not be able to communicate with
each other.
If
possible, avoid using explicit redistribution on NSSA ABR because confusion may
result over which packets are being translated by which router.
Configure Route
Summarization between OSPF Areas
Route
summarization is the consolidation of advertised addresses. This
feature causes a single summary route to be advertised to other areas by
an ABR. In OSPF, an ABR will advertise networks in one area into another area.
If the network numbers in an area are assigned in a way such that they are
contiguous, you can configure the ABR to advertise a summary route that covers
all the individual networks within the area that fall into the specified range.
To specify an address range,
perform the following task in router configuration mode:
Task
|
Command
|
Specify an address range
for which a single
|
area area-id range address mask [advertise |
|
route will be advertised.
|
not-advertise]
|
Configure Route Summarization when
Redistributing Routes into OSPF
Configure Route
Summarization when Redistributing Routes into OSPF
When redistributing routes from
other protocols into OSPF (as described in the chapter “Configuring IP Routing
Protocol-Independent Features”), each route is advertised individually in an
external link state advertisement (LSA). However, you can configure the Cisco
IOS software to advertise a single route for all the redistributed routes that
are covered by a specified network address and mask. Doing so helps decrease
the size of the OSPF link state database.
To have
the software advertise one summary route for all redistributed routes covered
by a network address and mask, perform the following task in router
configuration mode:
Task
|
Command
|
Specify
an address and mask that covers
|
summary-address address mask
|
redistributed
routes, so only one summary route is
|
|
advertised.
|
|
Create Virtual Links
In OSPF,
all areas must be connected to a backbone area. If there is a break in backbone
continuity, or the backbone is purposefully partitioned, you can establish a virtual
link. The two end points of a virtual link are Area Border Routers. The
virtual link must be configured in both routers. The configuration information
in each router consists of the other virtual endpoint (the other ABR), and the
nonbackbone area that the two routers have in common (called the transit
area). Note that virtual links cannot be configured through stub areas.
To establish a virtual link,
perform the following task in router configuration mode:
Task
|
Command
|
Establish a virtual link.
|
area area-id virtual-link router-id [hello-interval seconds]
|
[retransmit-interval seconds]
[transmit-delay seconds]
|
|
[dead-interval seconds] [[authentication-key
key] |
|
|
[message-digest-key keyid md5
key]]
|
|
To
display information about virtual links, use the show ip ospf virtual-links
EXEC command. To display the router ID of an OSPF router, use the show ip
ospf EXEC command.
Generate a Default
Route
You can
force an autonomous system boundary router to generate a default route into an
OSPF routing domain. Whenever you specifically configure redistribution of
routes into an OSPF routing domain, the router automatically becomes an
autonomous system boundary router. However, an autonomous system boundary
router does not, by default, generate a default route into the OSPF
routing domain.
To force
the autonomous system boundary router to generate a default route, perform the
following task in router configuration mode:
Task
|
Command
|
Force
the autonomous system boundary router
|
default-information
originate [always]
[metric
|
to
generate a default route into the OSPF
|
metric-value] [metric-type
type-value] [route-map
|
routing
domain.
|
map-name]
|
Configure Lookup of
DNS Names
See the
discussion of redistribution of routes in the “Configuring IP Routing
Protocol-Independent Features” chapter.
Configure Lookup of
DNS Names
You can configure OSPF to look up Domain Naming
System (DNS) names for use in all OSPF show command displays. This
feature makes it easier to identify a router, because it is displayed by name
rather than by its router ID or neighbor ID.
To configure DNS name lookup,
perform the following task in global configuration mode:
Task
|
Command
|
Configure
DNS name lookup.
|
ip ospf name-lookup
|
Force the Router ID
Choice with a Loopback Interface
OSPF uses
the largest IP address configured on the interfaces as its router ID. If the
interface associated with this IP address is ever brought down, or if the
address is removed, the OSPF process must recalculate a new router ID and
resend all its routing information out its interfaces.
If a
loopback interface is configured with an IP address, the Cisco IOS software
will use this IP address as its router ID, even if other interfaces have larger
IP addresses. Since loopback interfaces never go down, greater stability in the
routing table is achieved.
OSPF automatically prefers a loopback interface
over any other kind, and it chooses the highest IP address among all loopback
interfaces. If no loopback interfaces are present, the highest IP address in
the router is chosen. You cannot tell OSPF to use any particular interface.
To
configure an IP address on a loopback interface, perform the following tasks,
starting in global configuration mode:
Task
|
Command
|
|
Step 1
|
Create a loopback interface, which
|
interface loopback 0
|
places you in interface configuration
|
||
mode.
|
||
Step 2
|
Assign an IP address to this interface.
|
ip address address mask
|
Control Default
Metrics
In Cisco IOS Release 10.3 and later, by default,
OSPF calculates the OSPF metric for an interface according to the bandwidth of
the interface. For example, a 64K link gets a metric of 1562, while a T1 link
gets a metric of 64.
The OSPF
metric is calculated as ref-bw divided by bandwidth, with ref-bw
equal to 108 by default, and bandwidth
determined by the bandwidth command. The calculation gives FDDI a metric
of 1. If you have multiple links with high bandwidth, you might want to specify
a larger number to differentiate the cost on those links. To do so, perform the
following task in router configuration mode:
Task
|
Command
|
Differentiate
high bandwidth links.
|
ospf auto-cost
reference-bandwidth ref-bw
|
Configure OSPF on Simplex Ethernet
Interfaces
Configure OSPF on
Simplex Ethernet Interfaces
Because
simplex interfaces between two devices on an Ethernet represent only one
network segment, for OSPF you must configure the transmitting interface to be a
passive interface. This prevents OSPF from sending hello packets for the
transmitting interface. Both devices are able to see each other via the hello
packet generated for the receiving interface.
To
configure OSPF on simplex Ethernet interfaces, perform the following task in
router configuration mode:
Task
|
Command
|
Suppress
the sending of hello packets through
|
passive-interface type number
|
the
specified interface.
|
|
Configure Route
Calculation Timers
You can configure the delay time
between when OSPF receives a topology change and when it starts a shortest path
first (SPF) calculation. You can also configure the hold time between two
consecutive SPF calculations. To do this, perform the following task in router
configuration mode:
Task
|
Command
|
Configure route
calculation timers.
|
timers spf spf-delay spf-holdtime
|
Configure OSPF over
On Demand Circuits
The OSPF
on demand circuit is an enhancement to the OSPF protocol that allows efficient
operation over on demand circuits like ISDN, X.25 SVCs and dial-up lines. This
feature supports RFC 1793,
Extending OSPF to Support Demand
Circuits.
Prior to this feature, OSPF
periodic hello and link state advertisements (LSAs) updates would be exchanged
between routers that connected the on demand link, even when no changes
occurred in the hello or LSA information.
With this feature, periodic
hellos are suppressed and the periodic refreshes of LSAs are not flooded over
the demand circuit. These packets bring up the link only when they are
exchanged for the first time, or when a change occurs in the information they contain.
This operation allows the underlying datalink layer to be closed when the
network topology is stable.
This
feature is useful when you want to connect telecommuters or branch offices to
an OSPF backbone at a central site. In this case, OSPF for on demand circuits
allows the benefits of OSPF over the entire domain, without excess connection
costs. Periodic refreshes of hello updates, LSA updates, and other protocol
overhead are prevented from enabling the on demand circuit when there is no
“real” data to transmit.
Overhead
protocols such as hellos and LSAs are transferred over the on demand circuit
only upon initial setup and when they reflect a change in the topology. This
means that critical changes to the topology that require new SPF calculations
are transmitted in order to maintain network topology integrity. Periodic
refreshes that do not include changes, however, are not transmitted across the
link.
To
configure OSPF for on demand circuits, perform the following tasks, beginning
in global configuration mode:
Task
|
Command
|
|
Step 1
|
Enable OSPF operation.
|
router ospf process-id
|
Step 2
|
Configure OSPF on an on
demand circuit.
|
ip ospf demand-circuit
|
Log Neighbor Changes
If the
router is part of a point-to-point topology, then only one end of the demand
circuit must be configured with this command. However, all routers must have
this feature loaded.
If the
router is part of a point-to-multipoint topology, only the multipoint end must
be configured with this command.
Implementation
Considerations
Evaluate the following
considerations before implementing this feature:
•
Because LSAs that include topology changes are
flooded over an on demand circuit, it is advised to put demand circuits within
OSPF stub areas, or within NSSAs to isolate the demand circuits from as many
topology changes as possible.
•
To take advantage of the on demand circuit
functionality within a stub area or NSSA, every router in the area must have
this feature loaded. If this feature is deployed within a regular area, all
other regular areas must also support this feature before the demand circuit
functionality can take effect. This is because type 5 external LSAs are flooded
throughout all areas.
•
You do not want to do on a broadcast-based network
topology because the overhead protocols (such as hellos and LSAs) cannot be
successfully suppressed, which means the link will remain up.
Log Neighbor Changes
To
configure the router to send a syslog message when an OSPF neighbor state
changes, perform the following task in router configuration mode:
Task
|
Command
|
Send syslog message when
a neighbor state
|
ospf log-adj-changes
|
changes.
|
|
Configure
this command if you want to know about OSPF neighbor changes without turning on
the debugging command debug ip ospf adjacency. The ospf
log-adj-changes command provides a higher level view of changes to the
state of the peer relationship with less output.
Monitor and Maintain
OSPF
You can
display specific statistics such as the contents of IP routing tables, caches,
and databases. Information provided can be used to determine resource
utilization and solve network problems. You can also display information about
node reachability and discover the routing path your device’s packets are
taking through the network.
To display various routing
statistics, perform the following tasks in EXEC mode:
Task
|
Command
|
Display general
information about OSPF routing
|
show ip ospf [process-id]
|
processes.
|
|
OSPF Configuration Examples
Task
|
Command
|
|
Display
lists of information related to the OSPF
|
show ip ospf [process-id area-id]
database
|
|
database.
|
show ip ospf [process-id area-id]
database [router]
|
|
[link-state-id]
|
||
show ip ospf [process-id area-id]
database [network]
|
||
[link-state-id]
|
||
show ip ospf [process-id area-id]
database [summary]
|
||
[link-state-id]
|
||
show ip ospf [process-id area-id]
database
|
||
[asb-summary] [link-state-id]
|
||
show ip ospf [process-id]
database [external]
|
||
[link-state-id]
|
||
show ip ospf [process-id area-id]
database
|
||
[database-summary]
|
||
Display the internal OSPF
routing table entries to
|
show ip ospf
border-routers
|
|
Area Border Router (ABR)
and Autonomous
|
||
System Boundary Router
(ASBR).
|
||
Display OSPF-related
interface information.
|
show ip ospf interface [interface-name]
|
|
Display OSPF-neighbor
information on a
|
show ip ospf neighbor [interface-name] [neighbor-id]
|
|
per-interface basis.
|
detail
|
|
Display a list of all
LSAs requested by a router.
|
show ip ospf request-list
[nbr]
[intf] [intf-nbr]
|
|
Display a list of all
LSAs waiting to be
|
show ip ospf
retransmission-list [nbr]
[intf] [intf-nbr]
|
|
retransmitted.
|
||
Display OSPF-related
virtual links information.
|
show ip ospf
virtual-links
|
|
OSPF Configuration
Examples
The following sections provide
OSPF configuration examples:
OSPF
Point-to-Multipoint Example
In Figure 20, Mollie uses
DLCI 201 to communicate with Neon, DLCI 202 to Jelly, and DLCI 203 to Platty.
Neon uses DLCI 101 to communicate with Mollie and DLCI 102 to communicate with
Platty. Platty communicates with Neon (DLCI 401) and Mollie (DLCI 402). Jelly
communicates with Mollie (DLCI 301).
Mollie’s Configuration
hostname
mollie
!
interface
serial 1
ip
address 10.0.0.2 255.0.0.0
ip ospf
network point-to-multipoint encapsulation frame-relay
frame-relay map ip 10.0.0.1 201 broadcast
frame-relay map ip 10.0.0.3 202 broadcast frame-relay map ip 10.0.0.4 203
broadcast
!
router
ospf 1
network
10.0.0.0 0.0.0.255 area 0
Neon’s Configuration
hostname
neon
!
interface
serial 0
ip
address 10.0.0.1 255.0.0.0
ip ospf
network point-to-multipoint encapsulation frame-relay
frame-relay
map ip 10.0.0.2 101 broadcast frame-relay map ip 10.0.0.4 102 broadcast
!
router
ospf 1
network
10.0.0.0 0.0.0.255 area 0
Platty’s Configuration
hostname
platty
!
interface
serial 3
ip
address 10.0.0.4 255.0.0.0
ip ospf network point-to-multipoint
encapsulation frame-relay
clock rate
1000000
frame-relay
map ip 10.0.0.1 401 broadcast frame-relay map ip 10.0.0.2 402 broadcast
!
router
ospf 1
network
10.0.0.0 0.0.0.255 area 0
OSPF Configuration Examples
Jelly’s
Configuration
hostname
jelly
!
interface
serial 2
ip
address 10.0.0.3 255.0.0.0
ip ospf
network point-to-multipoint encapsulation frame-relay
clock rate
2000000
frame-relay
map ip 10.0.0.2
301 broadcast
!
router
ospf 1
network
10.0.0.0 0.0.0.255 area 0
Variable-Length
Subnet Masks Example
OSPF, static routes, and IS-IS
support variable-length subnet masks (VLSMs). With VLSMs, you can use different
masks for the same network number on different interfaces, which allows you to
conserve IP addresses and more efficiently use available address space.
In the
following example, a 30-bit subnet mask is used, leaving two bits of address
space reserved for serial line host addresses. There is sufficient host address
space for two host endpoints on a point-to-point serial link.
interface
ethernet 0
ip
address 131.107.1.1 255.255.255.0
!
8 bits of
host address space
reserved for ethernets
interface
serial 0
ip
address 131.107.254.1 255.255.255.252
! 2 bits
of address space
reserved for serial
lines
!
Router is configured for OSPF and assigned AS 107
router ospf 107
!
Specifies network directly connected to the router
network 131.107.0.0 0.0.255.255 area 0.0.0.0
OSPF
Routing and Route Redistribution Examples
OSPF
typically requires coordination among many internal routers, area border
routers, and autonomous system boundary routers. At a minimum, OSPF-based
routers can be configured with all default parameter values, with no
authentication, and with interfaces assigned to areas.
Three examples follow:
•
The
first is a simple configuration illustrating basic OSPF commands.
•
The second example illustrates a configuration for
an internal router, ABR, and ASBRs within a single, arbitrarily assigned, OSPF
autonomous system.
•
The third example illustrates a more complex
configuration and the application of various tools available for controlling
OSPF-based routing environments.
Basic OSPF Configuration Example
The
following example illustrates a simple OSPF configuration that enables OSPF
routing process 9000, attaches Ethernet 0 to area 0.0.0.0, and redistributes
RIP into OSPF, and OSPF into RIP:
interface
ethernet 0
ip address
130.93.1.1 255.255.255.0 ip ospf cost 1
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