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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 22 Configuring IP Unicast Routing
Configuring OSPF
•
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
“OSPF Interface Parameters” section on page 22-38
for parameter
definitions and
Table 22-7 on page 22-36
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 will be
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 default distance
for each type of route is 110. The range is 1 to 255.
Step 9
passive-interface type number
(Optional) Suppress the sending of hello packets through the
specified interface.
Step 10
timers spf spf-delay spf-holdtime
(Optional) Configure route calculation timers.
•
spf-delay—Enter an integer from 0 to 65535. The default is 5
seconds; 0 means no delay.
•
spf-holdtime—Enter an integer from 0 to 65535. The default is
10 seconds; 0 means no delay.
Step 11
ospf log-adj-changes
(Optional) Send syslog message when a neighbor state changes.
Step 12
end
Return to privileged EXEC mode.
Step 13
show ip ospf [process-id [area-id]] database Display lists of information related to the OSPF database for a
specific router. For some of the keyword options, see to the
“Monitoring OSPF” section on page 22-44
.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
