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Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
OL-12247-04
Chapter 38 Configuring IP Unicast Routing
Configuring OSPF
•
Default route: When you specifically configure redistribution of routes into an OSPF routing
domain, the route automatically becomes an autonomous system boundary router (ASBR). You can
force the ASBR to generate a default route into the OSPF routing domain.
•
Domain name server (DNS) names for use in all OSPF
show
privileged EXEC command displays
makes it easier to identify a router than displaying it by router ID or neighbor ID.
•
Default metrics: OSPF calculates the OSPF metric for an interface according to the bandwidth of
the interface. The metric is calculated as
ref-bw
divided by bandwidth, where
ref
is 10 by default,
and bandwidth (
bw
) is specified by the
bandwidth
interface configuration command. For multiple
links with high bandwidth, you can specify a larger number to differentiate the cost on those links.
•
Administrative distance is a rating of the trustworthiness of a routing information source, an integer
between 0 and 255, with a higher value meaning a lower trust rating. An administrative distance of
255 means the routing information source cannot be trusted at all and should be ignored. OSPF uses
three different administrative distances: routes within an area (intra-area), routes to another area
(interarea), and routes from another routing domain learned through redistribution (external). You
can change any of the distance values.
•
Passive interfaces: Because interfaces between two devices on an Ethernet represent only one
network segment, to prevent OSPF from sending hello packets for the sending interface, you must
configure the sending device to be a passive interface. Both devices can identify each other through
the hello packet for the receiving interface.
•
Route calculation timers: You can configure the delay time between when OSPF receives a topology
change and when it starts the shortest path first (SPF) calculation and the hold time between two
SPF calculations.
•
Log neighbor changes: You can configure the router to send a syslog message when an OSPF
neighbor state changes, providing a high-level view of changes in the router.
Beginning in privileged EXEC mode, follow these steps to configure these OSPF parameters:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
router ospf
process-id
Enable OSPF routing, and enter router configuration mode.
Step 3
summary-address
address mask
(Optional) Specify an address and IP subnet mask for redistributed
routes so that only one summary route is advertised.
Step 4
area
area-id
virtual-link
router-id
[
hello-interval
seconds
]
[
retransmit-interval
seconds
] [
trans
]
[[
authentication-key
key
] |
message-digest-key
keyid
md5
key
]]
(Optional) Establish a virtual link, and set its parameters. See the
“Configuring OSPF Interfaces” section on page 38-31
for parameter
definitions and
for virtual link defaults.
Step 5
default-information originate
[
always
]
[
metric
metric-value
] [
metric-type
type-value
] [
route-map
map-name
]
(Optional) Force the ASBR to generate a default route into the OSPF
routing domain. Parameters are all optional.
Step 6
ip ospf name-lookup
(Optional) Configure DNS name lookup. The default is disabled.
Step 7
ip auto-cost reference-bandwidth
ref-bw
(Optional) Specify an address range for which a single route is
advertised. Use this command only with area border routers.
Step 8
distance ospf
{[
inter-area
dist1
] [
inter-area
dist2
] [
external
dist3
]}
(Optional) Change the OSPF distance values. The range is 1 to 255.
The default distance for each type of route is 110.
Step 9
passive-interface
type number
(Optional) Suppress the sending of hello packets through the
specified interface.
