This article explains a scenario when the Native VLAN-ID is configured on one side whereas the other end is not having Native VLAN-ID configured.
By default, Juniper switches do not assign a Native VLAN to any trunked interface. The untagged packets are dropped on trunk interfaces. That is, if you do not configure the Native-VLAN-ID option on trunk interfaces, the untagged packets are dropped.
All the control messages are usually untagged and will continue to flow as usual. However if you have a Native-VLAN-ID configured on the interface, all the control messages will be tagged with the Native VLAN-ID. Now all the control traffic when received on the interface is expected to be tagged with the same Native-vlan ID otherwise the traffic is dropped. e.g if ARP request is sent out, an ARP reply is expected to be received with the same Native-vlan ID tag.
QFX5100-A
set interfaces xe-0/0/2 native-vlan-id 800
set interfaces xe-0/0/2 unit 0 family ethernet-switching interface-mode trunk
set interfaces xe-0/0/2 unit 0 family ethernet-switching vlan members 800-801
set interfaces irb unit 800 family inet address 10.10.80.1/24
set interfaces irb unit 801 family inet address 10.10.81.1/24
set vlans vlan_800 vlan-id 800
set vlans vlan_800 l3-interface irb.800
set vlans vlan_801 vlan-id 801
set vlans vlan_801 l3-interface irb.801
QFX5100-B
set interfaces irb unit 800 family inet address 10.10.80.2/24
set interfaces irb unit 801 family inet address 10.10.81.2/24
In the below example, we do not see any ARP for the irb.800 interface
labroot@qfx5100-a# run show arp no-resolve
MAC Address Address Interface Flags
f0:1c:2d:a8:a9:60 10.10.81.2 irb.801 [xe-0/0/2.0] none
labroot@qfx5100-b# run show arp no-resolve
f0:1c:2d:ac:d7:60 10.10.81.1 irb.801 [xe-0/0/2.0] noneWorkaround : "Remove the Native-vlan configuration from qfx5100-a" or "configure native vlan 800 on qfx5100-b"
Configure Native-VLAN with the same VLAN-ID on both sides of the trunk link otherwise a faulty state occurs