Traffic forwarding continues even after VLAN is deleted. This is due to "family ethernet-switching" config being present under the interface unit. This scenario is specifically seen on QFX5110.
On QFX5110 running Junos 17.3R2.10 with the following IFL config:
{master:0}
user@switch> show configuration groups CONFIG interfaces ae3000
description ServiceProvider4;
flexible-vlan-tagging;
mtu 9192;
encapsulation flexible-ethernet-services;
aggregated-ether-options {
minimum-links 1;
lacp {
active;
periodic fast;
}
}
unit 802 {
encapsulation vlan-bridge;
vlan-id-list 100-4094;
input-vlan-map push;
output-vlan-map pop;
family ethernet-switching;
}
And the IFL is part of the bridge domain:
{master:0}
user@switch> show vlans v802
Routing instance VLAN name Tag Interfaces
default-switch v802 NA
ae3000.802*
ae90.2002*
user@switch> show vlans v802 detail
Routing instance: default-switch
VLAN Name: v802 State: Active
Tag: NA
Internal index: 13, Generation Index: 14, Origin: Static
MAC aging time: 300 seconds
VXLAN Enabled : No
Interfaces:
ae3000.802*,tagged
ae90.2002*,tagged
Number of interfaces: Tagged 2 , Untagged 0
Total MAC count: 2
After removal of the bridge domain, it shows as Destroyed but the forwarding still continues:
user@switch# delete vlans v802
{master:0}
user@switch> show vlans v802 detail
Routing instance: default-switch
VLAN Name: v802 State: Destroyed
Tag: NA
Internal index: 13, Generation Index: 14, Origin: Static
MAC aging time: 300 seconds
VXLAN Enabled : No
Interfaces:
ae3000.802*,tagged
ae90.2002*,tagged
Number of interfaces: Tagged 2 , Untagged 0
Total MAC count: 2
user@switch> show vlans v802
Routing instance VLAN name Tag Interfaces
default-switch v802 NA
ae3000.802*
ae90.2002*
The issue occurs due to 'family ethernet-switching' on the 'vlan-bridge' encapsulated IFL.
For example, a warning message appears when we commit the configuration. But the VLAN still passes traffic.
{master:0}[edit]
user@switch# commit check
[edit interfaces]
'ge-0/0/2'
Configuration vlan-tagging is not supported with ifl family ethernet-switching
[edit interfaces]
The workaround is to remove 'family ethernet-switching' on the 'vlan-bridge' encapsulated IFL.