Learn the correct configuration steps to establish an OSPF neighbor relationship with a peer router after setting the passive-interface default command. Discover how to enable OSPF on a specific interface without modifying its configuration.
Table of Contents
Question
router(config)# router ospf 11 router(config-if)# passive-interface default
Refer to the exhibit. An engineer started to configure a router for OSPF. Which configuration must the engineer perform on the router without changing any interface configuration so that the router establishes an OSPF neighbor relationship with its peer?
A. router(config)# router ospf 11
router(config-if)# no passive-interface ethernet 1/1
B. router(config)# interface ethernet 1/1
router(config-if)# no shutdown
C. router(config)# interface ethernet 1/1
router(config-if)# ip ospf hello-interval
D. router(config)# interface ethernet 1/1
router(config-if)# ip ospf priority 0
Answer
A. router(config)# router ospf 11
router(config-if)# no passive-interface ethernet 1/1
Explanation
When configuring OSPF on a router, the “passive-interface default” command is used to set all interfaces as passive by default. Passive interfaces do not send or receive OSPF hello packets, effectively disabling OSPF neighbor discovery on those interfaces.
To establish an OSPF neighbor relationship with a peer router on a specific interface (in this case, Ethernet 1/1) without changing the interface configuration, you need to negate the passive-interface setting for that particular interface.
The “no passive-interface ethernet 1/1” command under the OSPF router configuration mode will enable OSPF on the Ethernet 1/1 interface, allowing it to send and receive OSPF hello packets and form a neighbor relationship with the peer router.
The other options are incorrect because:
B. The “no shutdown” command is used to administratively enable an interface, but it does not affect OSPF neighbor establishment.
C. The “ip ospf hello-interval” command is used to modify the OSPF hello packet interval, but it requires a value and does not directly enable OSPF on the interface.
D. The “ip ospf priority 0” command sets the OSPF router priority to 0, which prevents the router from becoming a designated router (DR) or backup designated router (BDR). It does not enable OSPF on the interface or establish neighbor relationships.
By issuing the “no passive-interface ethernet 1/1” command under the OSPF router configuration mode, the engineer can ensure that the router establishes an OSPF neighbor relationship with its peer on the Ethernet 1/1 interface without modifying the interface configuration.
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