Cisco Systems 3560 Manual De Usuario
36-32
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 36 Configuring IP Unicast Routing
Configuring OSPF
Configuring a Loopback Interface
OSPF uses the highest IP address configured on the interfaces as its router ID. If this interface is down
or 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, OSPF uses this IP address as
its router ID, even if other interfaces have higher IP addresses. Because loopback interfaces never fail,
this provides greater stability. OSPF automatically prefers a loopback interface over other interfaces, and
it chooses the highest IP address among all loopback interfaces.
or 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, OSPF uses this IP address as
its router ID, even if other interfaces have higher IP addresses. Because loopback interfaces never fail,
this provides greater stability. OSPF automatically prefers a loopback interface over other interfaces, and
it chooses the highest IP address among all loopback interfaces.
Beginning in privileged EXEC mode, follow these steps to configure a loopback interface:
Use the no interface loopback 0 global configuration command to disable the loopback interface.
Monitoring OSPF
You can display specific statistics such as the contents of IP routing tables, caches, and databases.
lists some of the privileged EXEC commands for displaying statistics. For more show ip ospf
database privileged EXEC command options and for explanations of fields in the resulting display, see
the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols, Release 12.2.
the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols, Release 12.2.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface loopback 0
Create a loopback interface, and enter interface configuration mode.
Step 3
ip address address mask
Assign an IP address to this interface.
Step 4
end
Return to privileged EXEC mode.
Step 5
show ip interface
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Table 36-6
Show IP OSPF Statistics Commands
Command
Purpose
show ip ospf [process-id]
Display general information about OSPF routing
processes.
processes.
show ip ospf [process-id] database [router] [link-state-id]
show ip ospf [process-id] database [router] [self-originate]
show ip ospf [process-id] database [router] [adv-router [ip-address]]
show ip ospf [process-id] database [network] [link-state-id]
show ip ospf [process-id] database [summary] [link-state-id]
show ip ospf [process-id] database [asbr-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 lists of information related to the OSPF
database.
database.
show ip ospf border-routes
Display the internal OSPF routing ABR and ASBR
table entries.
table entries.
show ip ospf interface [interface-name]
Display OSPF-related interface information.