Configuring Q-in-Q Tunneling
Q-in-Q tunneling and VLAN translation allow service providers to create a Layer 2 Ethernet connection between two customer sites. Providers can segregate different customers’ VLAN traffic on a link (for example, if the customers use overlapping VLAN IDs) or bundle different customer VLANs into a single service VLAN. Data centers can use Q-in-Q tunneling to isolate customer traffic within a single site or when customer traffic flows between cloud data centers in different geographic locations.
Before you begin setting up Q-in-Q tunneling, make sure you have created and configured the necessary customer VLANs on the neighboring switches. See Configuring VLANs.
To configure Q-in-Q tunneling:
- Create the service VLAN (S-VLAN) and configure an ID for
it:
[edit vlans]
user@switch# set s-vlan-name vlan-id s-vlan-ID - Enable Q-in-Q tunneling on the S-VLAN:
[edit vlans]
user@switch# set s-vlan-name dot1q-tunneling - Set the allowed customer VLANs (C-VLANs) on the S-VLAN
(optional). Here, the C-VLANs are identified by a range:
[edit vlans]
user@switch# set s-vlan-name dot1q-tunneling customer-vlans range - Configure a global value for the tag protocol identifier
(EtherType) of the service VLAN tags (optional):
[edit]
user@switch# set ethernet-switching-options dot1q-tunneling ether-type ether-type-value
Depending on your interface configuration, you might need to adjust the MTU value on your trunk or access ports to accommodate the 4 bytes used for the tag added by Q-in-Q tunneling. For example, if you use the default MTU value of 1514 bytes on your access and trunk ports, you need to make one of the following adjustments:
- Reduce the MTU on the access links by at least 4 bytes so that the frames do not exceed the MTU of the trunk link when S-VLAN tags are added.
- Increase the MTU on the trunk link so that the link can handle the larger frame size.
