According to JNCIP study guide(page 156) from 2003, the Junos should advertise a prefix on lo0.0 interface to OSPF if the RID is not manually configured:

JUNOS software automatically advertises a stub route to the interface from which the RID is obtained; therefore it is not actually necessary to explicitly configure lo0 as an OSPF interface to meet the lo0 connectivity requirements of this configuration example.

Has this behavior changed in the newer Junos releases? For example, with such configuration the address configured on lo0.0 interface is not advertised to OSPF:

root@r3> show configuration routing-options

root@r3> show configuration protocols ospf
area {
    interface ge-0/0/0.0;
    interface ge-0/0/1.0;

root@r3> show interfaces lo0.0 terse
Interface               Admin Link Proto    Local                 Remote
lo0.0                   up    up   inet            --> 0/0


1 Answer 1


Yes, this changed back in Junos 8.5. You must now explicitly configure lo0.0 (ideally as a passive interface) to advertise the network.

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