Hybrid Cloud Connectivity with QinQ and VXLANs

QinQ is an amendment to the IEEE 802.1Q specification that provides the capability for multiple VLAN tags to be inserted into a single Ethernet frame.

QinQ with VXLAN is typically used by a service provider who offers multi-tenant layer 2 connectivity between different customer data centers (private clouds) and also needs to connect those data centers to public cloud providers. Public clouds often has a mandatory QinQ handoff interface, where the outer tag is for the customer and the inner tag is for the service.

In Cumulus Linux, you map QinQ packets to VXLANs through:

  • Single tag translation, where you map a customer to a VNI and preserve the service as an inner VLAN inside a VXLAN packet.
  • Double tag translation, where you map a customer and service to a VNI.

QinQ is available on switches with the following ASCIs:

  • Broadcom Tomahawk 2, Tomahawk+, Tomahawk, Trident3, Trident II+ and Trident II.
  • Mellanox Spectrum, only with VLAN-aware bridges with 802.1ad and only with single tag translation.

Configure Single Tag Translation

Single tag translation adheres to the traditional QinQ service model. The customer-facing interface is a QinQ access port with the outer S-tag being the PVID, representing the customer. The S-tag is translated to a VXLAN VNI. The inner C-tag, which represents the service, is transparent to the provider. The public cloud handoff interface is a QinQ trunk where packets on the wire carry both the S-tag and the C-tag.

Single tag translation works with both VLAN-aware bridge mode and traditional bridge mode. However, single tag translation with VLAN-aware bridge mode is more scalable.

An example configuration in VLAN-aware bridge mode looks like this:

You configure two switches: one at the service provider edge that faces the customer (the switch on the left above), and one on the public cloud handoff edge (the switch on the right above).

To correctly interoperate, all edges must support QinQ with VXLANs.

Configure the Public Cloud-facing Switch

For the switch facing the public cloud:

  • Configure the bridge with vlan_protocol set to 802.1ad.
  • The VNI maps back to S-tag (customer).
  • A trunk port connected to the public cloud is the QinQ trunk and packets are double tagged, where the S-tag is for the customer and the C-tag is for the service.

To configure the public cloud-facing switch:

NCLU Commands

cumulus@switch:~$ net add vxlan vni-1000 vxlan id 1000
cumulus@switch:~$ net add vxlan vni-1000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-1000 bridge access 100
cumulus@switch:~$ net add vxlan vni-3000 vxlan id 3000
cumulus@switch:~$ net add vxlan vni-3000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-3000 bridge access 200
cumulus@switch:~$ net add bridge bridge vlan-protocol 802.1ad
cumulus@switch:~$ net add bridge bridge ports swp3,vni-1000,vni-3000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Linux Commands

Edit the /etc/network/interfaces file to add the following configuration:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vni-1000
iface vni-1000
    bridge-access 100
    vxlan-id 1000
    vxlan-local-tunnelip 10.0.0.1

auto vni-3000
iface vni-3000
    bridge-access 200
    vxlan-id 3000
    vxlan-local-tunnelip 10.0.0.1

auto bridge
iface bridge
    bridge-ports swp3 vni-1000 vni-3000
    bridge-vids 100 200
    bridge-vlan-aware yes
    bridge-vlan-protocol 802.1ad
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Configure the Customer-facing Edge Switch

For the switch facing the customer:

  • Configure the bridge with vlan_protocol set to 802.1ad.
  • The customer interface is the QinQ access port, the PVID is the S-tag (customer) and is mapped to a VNI.
  • The service VLAN tags (C-tags) are preserved during VXLAN encapsulation.

To configure the customer-facing switch:

NCLU Commands

cumulus@switch:~$ net add interface swp3 bridge access 100
cumulus@switch:~$ net add interface swp4 bridge access 200
cumulus@switch:~$ net add vxlan vni-1000 vxlan id 1000
cumulus@switch:~$ net add vxlan vni-1000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-1000 bridge access 100
cumulus@switch:~$ net add vxlan vni-3000 vxlan id 3000
cumulus@switch:~$ net add vxlan vni-3000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-3000 bridge access 200
cumulus@switch:~$ net add bridge bridge ports swp3,swp4,vni-1000,vni-3000
cumulus@switch:~$ net add bridge bridge vlan-protocol 802.1ad
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Linux Commands

Edit the /etc/network/interfaces file to add the following configuration:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vni-1000
iface vni-1000
    bridge-access 100
    vxlan-id 1000
    vxlan-local-tunnelip 10.0.0.1

auto vni-3000
iface vni-3000
    bridge-access 200
    vxlan-id 3000
    vxlan-local-tunnelip 10.0.0.1

auto swp3
iface swp3
    bridge-access 100

auto swp4
iface swp4
    bridge-access 200

auto bridge
iface bridge
    bridge-ports swp3 swp4 vni-1000 vni-3000
    bridge-vids 100 200
    bridge-vlan-aware yes
    bridge-vlan-protocol 802.1ad
...

View the Configuration

In the output below, customer A is on VLAN 100 (S-TAG) and customer B is on VLAN 200 (S-TAG).

To check the public cloud-facing switch, run the net show bridge vlan command:

cumulus@switch:~$ net show bridge vlan

Interface      VLAN  Flags                  VNI
-----------  ------  ---------------------  -----
swp3             1   PVID, Egress Untagged
               100
               200
vni-1000       100   PVID, Egress Untagged   1000
vni-3000       200   PVID, Egress Untagged   3000

To check the customer-facing switch, use net show bridge vlan:

cumulus@switch:~$ net show bridge vlan
Interface      VLAN  Flags                  VNI
-----------  ------  ---------------------  -----
swp3            100  PVID, Egress Untagged
swp4            200  PVID, Egress Untagged
vni-1000        100  PVID, Egress Untagged  1000
vni-3000        200  PVID, Egress Untagged  3000

To verify that the bridge is configured for QinQ, run ip -d link show bridge and look for vlan_protocol 802.1ad in the output:

cumulus@switch:~$ sudo ip -d link show bridge
287: bridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
    link/ether 06:a2:ae:de:e3:43 brd ff:ff:ff:ff:ff:ff promiscuity 0
    bridge forward_delay 1500 hello_time 200 max_age 2000 ageing_time 30000 stp_state 2 priority 32768 vlan_filtering 1 vlan_protocol 802.1ad bridge_id 8000.6:a2:ae:de:e3:43 designated_root 8000.6:a2:ae:de:e3:43 root_port 0 root_path_cost 0 topology_change 0 topology_change_detected 0 hello_timer    0.00 tcn_timer    0.00 topology_change_timer    0.00 gc_timer   64.29 vlan_default_pvid 1 vlan_stats_enabled 1 group_fwd_mask 0 group_address 01:80:c2:00:00:08 mcast_snooping 0 mcast_router 1 mcast_query_use_ifaddr 0 mcast_querier 0 mcast_hash_elasticity 4096 mcast_hash_max 4096 mcast_last_member_count 2 mcast_startup_query_count 2 mcast_last_member_interval 100 mcast_membership_interval 26000 mcast_querier_interval 25500 mcast_query_interval 12500 mcast_query_response_interval 1000 mcast_startup_query_interval 3125 mcast_stats_enabled 1 mcast_igmp_version 2 mcast_mld_version 1 nf_call_iptables 0 nf_call_ip6tables 0 nf_call_arptables 0 addrgenmode eui64

Example Configuration in Traditional Bridge Mode

An example configuration for single tag translation in traditional bridge mode on a leaf switch is shown below.

Example /etc/network/interfaces File

uto swp3.11
iface swp3.11
    vlan-protocol 802.1ad

auto vxlan1000101
iface vxlan1000101
    vxlan-id 1000101
    vxlan-local-tunnelip 10.0.0.13

auto br11
iface br11
    bridge-ports swp3.11 vxlan1000101

Configure Double Tag Translation

Double tag translation involves a bridge with double-tagged member interfaces, where a combination of the C-tag and S-tag map to a VNI. You create the configuration only at the edge facing the public cloud. The VXLAN configuration at the customer-facing edge doesn’t need to change.

The double tag is always a cloud connection. The customer-facing edge is either single-tagged or untagged. At the public cloud handoff point, the VNI maps to double VLAN tags, with the S-tag indicating the customer and the C-tag indicating the service.

The configuration in Cumulus Linux uses the outer tag for the customer and the inner tag for the service.

You configure a double-tagged interface by stacking the VLANs in the following manner: <port>.<outer tag>.<inner tag>. For example, consider swp1.100.10: the outer tag is VLAN 100, which represents the customer, and the inner tag is VLAN 10, which represents the service.

The outer tag or TPID (tagged protocol identifier) needs the vlan_protocol to be specified. It can be either 802.1Q or 802.1ad. If 802.1ad is used, it must be specified on the lower VLAN device, such as swp3.100 in the example below.

Double tag translation only works with bridges in traditional mode (not VLAN-aware mode).

An example configuration:

To configure the switch for double tag translation using the above example, edit the /etc/network/interfaces file in a text editor and add the following:

auto swp3.100
iface swp3.100
    vlan_protocol 802.1ad

auto swp3.100.10
iface swp3.100.10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes

auto vni1000
iface vni1000
    vxlan-local-tunnelip  10.0.0.1
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    vxlan-id 1000

auto custA-10-azr
iface custA-10-azr
    bridge-ports swp3.100.10 vni1000
    bridge-vlan-aware no

To check the configuration, run the brctl show command:

cumulus@switch:~$ sudo brctl show
bridge name     bridge id               STP enabled     interfaces
custA-10-azr    8000.00020000004b       yes             swp3.100.10
                                                        vni1000
custB-20-azr    8000.00020000004b       yes             swp3.200.20
                                                        vni3000

If the bridge is not VXLAN-enabled, the configuration looks like this:

auto swp5.100
iface swp5.100
    vlan-protocol 802.1ad

auto swp5.100.10
iface swp5.100.10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes

auto br10
iface br10
    bridge-ports swp3.10  swp4  swp5.100.10
    bridge-vlan-aware no

Caveats and Errata

Feature Limitations

  • iptables match on double-tagged interfaces is not supported.
  • MLAG is only supported with single-tagged translation.
  • Mixing 802.1Q and 802.1ad subinterfaces on the same switch port is not supported.
  • When configuring bridges in traditional mode, all VLANs that are members of the same switch port must use the same vlan_protocol.
  • When using switches with Mellanox Spectrum ASICs in an MLAG pair:
    • Configure the peerlink (peerlink.4094) between the MLAG pair for VLAN protocol 802.1ad.
    • You cannot use the peerlink as a backup datapath in case one of the MLAG peers loses all uplinks.
  • For switches with the Spectrum ASIC (but not the Spectrum 2), when the bridge VLAN protocol is 802.1ad and is VXLAN-enabled, either:
    • All bridge ports are access ports, except for the MLAG peerlink.
    • All bridge ports are VLAN trunks. This means the switch terminating the cloud provider connections (double-tagged) cannot have local clients; these clients must be on a separate switch.

Long Interface Names

The Linux kernel limits interface names to 15 characters in length. For QinQ interfaces, you can reach this limit easily.

To work around this issue, create two VLANs as nested VLAN raw devices, one for the outer tag and one for the inner tag. For example, you cannot create an interface called swp50s0.1001.101 because it contains 16 characters. Instead, edit the /etc/network/interfaces file to create VLANs with IDs 1001 and 101. For example:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vlan1001
iface vlan1001
      vlan-id 1001
       vlan-raw-device swp50s0
       vlan-protocol 802.1ad

auto vlan1001-101
iface vlan1001-101
       vlan-id 101
       vlan-raw-device vlan1001

auto bridge101
iface bridge101
    bridge-ports vlan1001-101 vxlan1000101
...