Starting from JUNOS 8.1 Juniper introduce new feature on GE interface, called flexible vlan tagging.
This features are supported by GE IQ2 interfaces.
“flexible” term means that they allow you to configure logical unit on interfaces with vlan combination either dual, single and untag.
Ethernet frame can be configured as untagged, single tagged or dual tagged (stacked vlan).
In previous version of JUNOS, we cannot configure logical interface with mix configuration between single tagged and dual tagged. So, if you have 2 logical interface in the same physical port, you cannot configure one logical interface with single tag and another logical interface with dual tag.
The configuration is very simple. Just put flexible-vlan-tagging syntax under GE IQ2 physical interface.
Under logical interface, we can configure vlan inner and outer simultaneously.
Look at this example:
vlan-tags outer 0×8100.100 inner 0×8100.101;
This logical interface will have vlan outer 100 and vlan inner 101.
Each vlan has 4bytes overhead. So, stacked vlan need additional header 4 bytes than single tag.
What is 0×8100?
0×8100 is TPID (Tag protocol identifier).
Juniper used 0×8100 for TPID, but another vendor like Extreme Networks using TPID 0×9100.
Juniper called dual tagged vlan with Stacked Vlan, another vendor call it with QinQ.
Just different term, but have the same concept. J
This technology is widely adapted in Metro Ethernet networks and some used it for Ethernet aggregation router and L2VPN.
For the additional example how to configure interface to accept untagged frame can be shown below:
I draw this sample diagram.
C1-------------C2
Actually C1 and C2 is logical router which directly connected using 4xGE IQ2 PIC.
Below is the configuration of C1
enugadi@prime# show interfaces ge-2/1/3
flexible-vlan-tagging;
native-vlan-id 1;
{master}[edit]
enugadi@prime# show logical-systems c1
interfaces {
ge-2/1/3 {
unit 0 {
vlan-id 1;
family inet {
address 50.0.0.1/24;
}
}
}
}
Native-Vlan-Id is needed to be configured. Interface ge-2/1/3 will send untagged packet through this interface.
Below is configuration of C2
enugadi@prime# show interfaces ge-2/0/0
unit 0 {
family inet {
address 50.0.0.2/24;
}
}
There is no vlan-id configuration on interface ge-2/0/0.
Test result:
native-vlan-id 1; enugadi@prime# run ping 50.0.0.2 logical-system c1 PING 50.0.0.2 (50.0.0.2): 56 data bytes 64 bytes from 50.0.0.2: icmp_seq=0 ttl=64 time=0.442 ms 64 bytes from 50.0.0.2: icmp_seq=1 ttl=64 time=0.278 ms 64 bytes from 50.0.0.2: icmp_seq=2 ttl=64 time=0.274 ms 64 bytes from 50.0.0.2: icmp_seq=3 ttl=64 time=0.270 ms ^C --- 50.0.0.2 ping statistics --- 4 packets transmitted, 4 packets received, 0% packet loss round-trip min/avg/max/stddev = 0.270/0.316/0.442/0.073 ms
