Q-in-Q was introduced for the EX-series Switch starting with Junos OS Release 9.3. This article provides a summary of how it functions and a configuration example.

Note: Additional examples and information can be found in Understanding Q-in-Q Tunneling on EX-series Switches.

 

Q-in-Q tunneling allows service providers on Ethernet access networks to extend a Layer 2 Ethernet connection between two customer sites. Using Q-in-Q tunneling, providers can also segregate or bundle customer traffic into fewer VLANs or different VLANs by adding another layer of 802.1Q tags. Q-in-Q tunneling is useful when customers have overlapping VLAN IDs, because the customer’s 802.1Q (dot1Q) VLAN tags are prepended by the service VLAN (S-VLAN) tag. The Junos OS software implementation of Q-in-Q tunneling supports the IEEE 802.1ad standard.

The following example outlines a Q-in-Q topology and configuration.

• Customer tagged traffic comes in on ge-0/0/1 and ge-0/0/3, and is sent across ge-0/0/4 (cloud) preserved, and ge-0/0/15 gets the tagged traffic.

• SW1 and SW2 are provider edge switches in the cloud, interfacing the customer at location 1 (SW1) and location 2 (SW2). These 2 switches do not need the MTU setting because the EX switch takes care of that. However, the intermediate switches in the cloud need Layer 2 MTU increased by 4 for the outer tag.

• Note that ge-0/0/1, 3, and 15 are access ports, and ge-0/0/4 carries only customer VLAN 4001.

Note: Later Junos OS software releases for the EX-series switch will have complete L2TP support, where a customer’s untagged traffic and control packets can also be transported. Then customer switches can also run MSTP load-balancing if they interface into redundant SP clouds.



SW1
=========

• ge-0/0/1 and ge-0/0/3 are access ports.
• ge-0/04 is the trunk port.

root# show ethernet-switching-options
dot1q-tunneling {
    ether-type 0x8100;
}

root# show vlans
qinqvlan {
    vlan-id 4001;
    interface {
        ge-0/0/1.0;
        ge-0/0/3.0
    }
    dot1q-tunneling {
        customer-vlans 1-4094;
    }
}

root# show interfaces ge-0/0/4
unit 0 {
    family ethernet-switching {
        port-mode trunk;
        vlan {
            members 4001;
        }
    }
}

root# show interfaces ge-0/0/1
unit 0 {
    family ethernet-switching;
}

root# show interfaces ge-0/0/3
unit 0 {
    family ethernet-switching;
}

SW2
=======

• ge-0/0/15 is an access port.
• ge-0/0/4 is a trunk port.

root# show ethernet-switching-options
dot1q-tunneling {
    ether-type 0x8100;
}

root# show vlans
qinqvlan {
    vlan-id 4001;
    interface {
        ge-0/0/15.0;
    }
    dot1q-tunneling {
        customer-vlans 1-4094;
    }
}

root# show interfaces ge-0/0/4
unit 0 {
    family ethernet-switching {
        port-mode trunk;
        vlan {
            members 4001;
        }
    }
}

root# show interfaces ge-0/0/15
unit 0 {
    family ethernet-switching;
} 

 

2020-01-21: Article checked for accuracy and validity and found up-to-date; topology diagram changed along with minor name changes