An interface in JUNOS can have multiple logical interfaces.
Physical interface ge-0/0/0 can look like this:
ge-0/0/0.0 - unit 0 aka logical interface 0
ge-0/0/0.100 - unit 100 aka logical interface 100
The unit just denotes the logical interface that you are using when assigning an IP address, etc.
A good practice is to make your unit the same number as your VLAN-ID.
We are in the process of phasing out HP ProCurve switches in favor of EX switches so we had do some work on handling the native VLAN on an EX.
We can say the following about JUNOS and the native VLAN:
- By default each JUNOS EX device includes a common default VLAN named 'default'
- The default VLAN is untagged and does not have a VLAN ID associated with it
- EX trunk ports do not accept untagged traffic
You can tell JUNOS to handle default VLAN traffic over a trunk port like this.
Assume that port ge-0/0/49 is an uplink/trunk interface:
root@sriracha edit interfaces
root@sriracha# set ge-0/0/049 unit 0 family ethernet-switching native-vlan-id default
root@sriracha# commit comment "Added native VLAN to trunk port ge-0/0/49"
If you run 'show vlans detail' from operational mode you will see that the default VLAN is shown on the trunk port(s) in an untagged state.
You can associate a VLAN ID to the default VLAN like this:
root@sriracha# set vlans default vlan-id 1
root@sriracha# commit comment "Added VLAN ID 1 to default VLAN"