For instance, R1 is connected to R2.
This is config will maintain only Level 1 adjancey between the two.
Router1
set interfaces fe-1/2/0 unit 0 description to-R2
set interfaces fe-1/2/0 unit 0 family inet address XX.0.0.X/30
set interfaces fe-1/2/0 unit 0 family iso
set interfaces lo0 unit 0 family inet address X.X.X.X/32
set interfaces lo0 unit 0 family iso address 49.002.0192.0168.0006.00
set protocols isis interface fe-1/2/0.0 level 2 disable
set protocols isis interface lo0.0 level 2 disable
Router2
set interfaces fe-1/2/0 unit 0 description to-R1
set interfaces fe-1/2/0 unit 0 family inet address XX.0.0.X/30
set interfaces fe-1/2/0 unit 0 family iso
set interfaces lo0 unit 0 family inet address X.X.X.X/32
set interfaces lo0 unit 0 family iso address 49.002.0192.0168.0007.00
set protocols isis interface fe-1/2/0.0 level 2 disable
set protocols isis interface lo0.0 level 2 disable