juniper-nuances-part1

Once day I was relaiming an interface on my newly aquired Juniper SRX300 (yes, I managed to get one of these nice little units!) and when trying to commit, I came accross the below error, which wile it seems a little misleading, it actually gives a very good clue at the issue (which may seem cryptic to the inexperienced user).

root@srx300# set interfaces ge-0/0/1 unit 0 family ethernet-switching interface-mode trunk
[edit]
root@srx300# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members all
[edit]
root@srx300# commit check
[edit routing-instances emetric interface]
  'ge-0/0/1.0'
    Interface with 'interface-mode' is allowed only in a virtual-switch
error: configuration check-out failed: (statements constraint check failed)

In the above example, the system claims that 'the interface-mode is allowed only in a virtual-switch' however upon removing the associated interface from the routing-instance (in this case I just deleted the routing instance) and making sure that the following was in place, then commit was successful and no further errors.

[edit]
root@srx300# delete routing-instances emetric
[edit]
root@srx300# commit check
configuration check succeeds
[edit]
root@srx300# show interfaces ge-0/0/1 | display set
set interfaces ge-0/0/1 unit 0 family ethernet-switching interface-mode trunk
set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members all

So, you see the lesson here is READ the output carfeully for the clue as to why the commit is throwing an error. In my case the interface was assigned in a routing-instance and therefore mutually exclusive when the interface is a L2 trunk (highlighted text).