Hi sarahr202,
Howdy, unfortunately since the loopback interface is special a virtual interface this is not possible. A virtual interface is not able to physically transmit any data or physically receive any data. If the loopback can not send OSPF hello messages or receive OSPF hello messages then it is not possible to establish any neighbor relationship using loopback interfaces. Nevertheless, you can use an IRB for this purpose as the IRB is mapped to VLAN which at the same time will take advantage of the physical infrastructure from any layer 2 interfaces assigned to this VLAN if/when needed, in other words, the IRB would be able to send hellos and they will do It through the VLAN they are par of.
As you can see here Lo0 is not even capable of sending hellos
{master:0}[edit]
root@LilDexx# run monitor traffic interface lo0 size 1500 no-resolve matching "host 224.0.0.5"
verbose output suppressed, use <detail> or <extensive> for full protocol decode
Address resolution is OFF.
Listening on lo0, capture size 1500 bytes
371 packets received by filter
0 packets dropped by kernel
{master:0}[edit]
IRB interfaces are 🙂
root@LilDexx# run monitor traffic interface irb size 1500 no-resolve matching "host 224.0.0.5"
verbose output suppressed, use <detail> or <extensive> for full protocol decode
Address resolution is OFF.
Listening on irb, capture size 1500 bytes
13:57:23.747812 In IP 12.34.56.1 > 224.0.0.5: OSPFv2, Hello, length 60
13:57:26.944445 Out IP 12.34.56.2 > 224.0.0.5: OSPFv2, Hello, length 60
2 packets received by filter
0 packets dropped by kernel
If this solves your problem, please mark this post as "Accepted Solution" so we can help others too \:)/
Regards,
Lil Dexx
JNCIE-ENT#863, 3X JNCIP-[SP-ENT-DC], 4X JNCIA [cloud-DevOps-Junos-Design], Champions Ingenius, SSYB