On ELS switches running Junos OS, interfaces configured with family ethernet-switching but without an explicit VLAN, membership are automatically placed in the default VLAN.

*Note*:

"By default, when you boot the switch and do not explicitly configure a port mode, all interfaces on the switch are in access mode and accept only untagged packets from the default VLAN."

Bridging and VLANs | Junos OS | Juniper Networks

Renaming this VLAN can lead to unexpected behavior where access interfaces stop learning MAC addresses. This condition will affect dynamic VLAN assignment through dot1x since the port configuration typically requires that no explicit VLAN be assigned to the interface.

Default scenario:

No explicit vlan assigned to port ge-0/0/1, no vlan-id 1 configured.

root@EX34> show configuration interfaces ge-0/0/1

unit 0 {

  family ethernet-switching;

}

root@EX34> show configuration vlans

v991 {

  vlan-id 991;

}

The output below shows the port assigned to vlan default 1.

root@EX34> show ethernet-switching interface ge-0/0/1

Logical     Vlan          TAG  MAC  MAC+IP STP     Logical     Tagging

interface    members           limit limit state    interface flags

ge-0/0/1.0                  32768 0         DN        untagged

        default        1   32768 0   Discarding          untagged

In the example below:

No explicit vlan assigned to port ge-0/0/1, vlan-id 1 renamed to "v1":

root@EX34> show configuration interfaces ge-0/0/1

unit 0 {

  family ethernet-switching;

}

root@EX34> show configuration vlans

v1 {

  vlan-id 1;

}

v991 {

  vlan-id 991;

}

Per the output below, port ge-0/0/1 that did not have vlan members explicitly configured end up without an operational VLAN.

{master:0}

root@EX34> show ethernet-switching interface ge-0/0/1

Logical     Vlan          TAG  MAC  MAC+IP STP     Logical     Tagging

interface    members           limit limit state    interface flags

ge-0/0/1.0                  32768 0         DN        untagged

MAC address learning does not occur, preventing 802.1X authentication from being initiated.

There are three possible options:

Option 1 – Avoid renaming VLAN ID 1

If vlan-id 1 name is modified, the internal reference to default no longer matches the VLAN 1.

#set vlans default vlan-id 1

root@EX34> show ethernet-switching interface ge-0/0/1

Logical     Vlan          TAG  MAC  MAC+IP STP     Logical     Tagging

interface    members           limit limit state    interface flags

ge-0/0/1.0                  32768 0         DN        untagged

        default        1   32768 0   Discarding          untagged

Option 2 – Delete VLAN ID 1

Delete vlan 1. Deleting vlan-id 1 restores the default behavior where interfaces without an explicitly configured VLAN are automatically assigned to vlan default 1.

#delete vlans v1 vlan-id 1

root@EX34> show configuration vlans

v991 {

  vlan-id 991;

}

root@EX34> show ethernet-switching interface ge-0/0/1

Logical     Vlan          TAG  MAC  MAC+IP STP     Logical     Tagging

interface    members           limit limit state    interface flags

ge-0/0/1.0                  32768 0         DN        untagged

        default        1   32768 0   Discarding          untagged

Option 3 – Recreate the default VLAN

If VLAN ID 1 must be renamed, create a VLAN named default and assign it a different VLAN ID in order to maintain an operational default VLAN.

root@EX34# set vlans v1 vlan-id 1

root@EX34# set vlans default vlan-id 13

root@EX34> show ethernet-switching interface ge-0/0/1

Logical     Vlan          TAG  MAC  MAC+IP STP     Logical     Tagging

interface    members           limit limit state    interface flags

ge-0/0/1.0                  32768 0         DN        untagged

        default        13  32768 0   Discarding          untagged