31-35
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 31 Configuring IP Unicast Routing
Configuring OSPF
• 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 31-32 for parameter
definitions and Table 31-7 on page 31-30 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 31-37.
Step 14
copy running-config startup-config (Optional) Save your entries in the configuration file.
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