VLAN-aware Bridge Mode

VLAN-aware bridge mode in Cumulus Linux implements a configuration model for large-scale layer 2 environments, with one single instance of spanning tree protocol. Each physical bridge member port includes the list of allowed VLANs as well as the port VLAN ID, either the primary VLAN Identifier (PVID) or native VLAN. MAC address learning, filtering and forwarding are VLAN-aware. This reduces the configuration size, and eliminates the large overhead of managing the port and VLAN instances as subinterfaces, replacing them with lightweight VLAN bitmaps and state updates.

On NVIDIA Spectrum-2 and Spectrum-3 switches, Cumulus Linux supports multiple VLAN-aware bridges but with the following limitations:

  • You cannot use MLAG with multiple VLAN-aware bridges
  • You cannot use the same port with multiple VLAN-aware bridges
  • You cannot use the same VNIs in multiple VLAN-aware bridges
  • You cannot use VLAN translation with multiple VLAN-aware bridges
  • You cannot use double tagged VLAN interfaces with multiple VLAN-aware bridges
  • You cannot associate multiple single VXLAN devices (SVDs) with a single VLAN-aware bridge
  • Cumulus Linux does not support IGMPv3.

Configure a VLAN-aware Bridge

The example commands below create a VLAN-aware bridge for STP that contains two switch ports and includes 3 VLANs; tagged VLANs 10 and 20, and untagged (native) VLAN 1.

cumulus@switch:~$ net add bridge bridge ports swp1-2
cumulus@switch:~$ net add bridge bridge vids 10,20
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following code snippet in the /etc/network/interfaces file:

auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 20
    bridge-vlan-aware yes

With NVUE, there is a default bridge called br_default, which has no ports assigned. The example below configures this default bridge.

cumulus@switch:~$ nv set interface swp1-2 bridge domain br_default
cumulus@switch:~$ nv set bridge domain br_default vlan 10,20
cumulus@switch:~$ nv set bridge domain br_default untagged 1
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file and add the bridge:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-vids 10 20
    bridge-pvid 1
    bridge-vlan-aware yes
...

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

cumulus@switch:~$ ifreload -a

The Primary VLAN Identifier (PVID) of the bridge defaults to 1. You do not have to specify bridge-pvid for a bridge or a port. However, even though this does not affect the configuration, it helps other users for readability. The following configurations are identical to each other and the configuration above:

auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-vids 1 10 20
    bridge-vlan-aware yes
auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 1 10 20
    bridge-vlan-aware yes
auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-vids 10 20
    bridge-vlan-aware yes

  • If you specify bridge-vids or bridge-pvid at the bridge level, all ports in the bridge inherit these configurations. However, specifying any of these settings for a specific port overrides the setting in the bridge.
  • Do not bridge the management port eth0 with any switch ports. For example, if you create a bridge with eth0 and swp1, the bridge does not work correctly and disrupts access to the management interface.

Configure Multiple VLAN-aware Bridges

This example shows the commands required to create two VLAN-aware bridges on the switch.

  • bridge1 bridges swp1 and swp2, and includes 2 VLANs; vlan 10 and vlan 20
  • bridge2 bridges swp3 and contains one VLAN; vlan 10

Bridges are independent so you can reuse VLANs between bridges. Each VLAN-aware bridge maintains its own MAC address and VLAN tag table; MAC and VLAN tags in one bridge are not visible to the other table.

cumulus@switch:~$ net add bridge bridge1 ports swp1-2
cumulus@switch:~$ net add bridge bridge1 vids 10,20
cumulus@switch:~$ net add bridge bridge1 pvid 1
cumulus@switch:~$ net add bridge bridge2 ports swp3
cumulus@switch:~$ net add bridge bridge2 vids 10
cumulus@switch:~$ net add bridge bridge2 pvid 1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ nv set interface swp1-2 bridge domain bridge1
cumulus@switch:~$ nv set bridge domain bridge1 vlan 10,20
cumulus@switch:~$ nv set bridge domain bridge1 untagged 1
cumulus@switch:~$ nv set interface swp3 bridge domain bridge2
cumulus@switch:~$ nv set bridge domain bridge2 vlan 10
cumulus@switch:~$ nv set bridge domain bridge2 untagged 1
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file and add the bridge:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge1
iface bridge1
    bridge-ports swp1 swp2
    bridge-vlan-aware yes
    bridge-vids 10 20
    bridge-pvid 1

auto bridge2
iface bridge2
    bridge-ports swp3
    bridge-vlan-aware yes
    bridge-vids 10
    bridge-pvid 1
...

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

cumulus@switch:~$ ifreload -a

NVIDIA Spectrum switches support a maximum of 6000 VLAN elements and calculate the total number of VLAN elements as the number of VLANs times the number of configured bridges. For example, 6 bridges, each containing 1000 VLANS totals 6000 VLAN elements.

Reserved VLAN Range

For hardware data plane internal operations, the switching silicon requires VLANs for every physical port, Linux bridge, and layer 3 subinterface. Cumulus Linux reserves a range of VLANs by default; the reserved range is 3725-3999.

If the reserved VLAN range conflicts with any user-defined VLANs, you can modify the range. The new range must be a contiguous set of VLANs with IDs between 2 and 4094. For a single VLAN-aware bridge, the minimum size of the range is 2 VLANs. For multiple VLAN-aware bridges, the minimum size of the range is the number of VLAN-aware bridges on the system plus one.

To configure the reserved range, edit the /etc/cumulus/switchd.conf file to uncomment the resv_vlan_range line and specify a new range. After you save the file, you must restart switchd.

VLAN Pruning

By default, the bridge port inherits the bridge VIDs, however, you can configure a port to override the bridge VIDs.

This example commands configure swp3 to override the bridge VIDs:

cumulus@switch:~$ net add bridge bridge ports swp1-3
cumulus@switch:~$ net add bridge bridge vids 10,20
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add interface swp3 bridge vids 20
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ nv set interface swp1-3 bridge domain br_default
cumulus@switch:~$ nv set bridge domain br_default vlan 10,20
cumulus@switch:~$ nv set bridge domain br_default untagged 1
cumulus@switch:~$ nv set interface swp3 bridge domain br_default vlan 20
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file, then run the ifreload -a command. The following example commands configure swp3 to override the bridge VIDs:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto br_default
iface br_default
    bridge-ports swp1 swp2 swp3
    bridge-pvid 1
    bridge-vids 10 20
    bridge-vlan-aware yes

auto swp3
iface swp3
  bridge-vids 20
...
cumulus@switch:~$ ifreload -a

Access Ports and Tagged Packets

Access ports ignore all tagged packets. In the configuration below, swp1 and swp2 are access ports, while all untagged traffic goes to VLAN 10:

cumulus@switch:~$ net add bridge bridge ports swp1-2
cumulus@switch:~$ net add bridge bridge vids 10,20
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add interface swp1 bridge access 10
cumulus@switch:~$ net add interface swp2 bridge access 10
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ nv set interface swp1-2 bridge domain br_default
cumulus@switch:~$ nv set bridge domain br_default vlan 10,20
cumulus@switch:~$ nv set bridge domain br_default untagged 1
cumulus@switch:~$ nv set interface swp1 bridge domain br_default access 10
cumulus@switch:~$ nv set interface swp2 bridge domain br_default access 10
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file, then run the ifreload -a command.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 20
    bridge-vlan-aware yes

auto swp1
iface swp1
    bridge-access 10

auto swp2
iface swp2
    bridge-access 10
...
cumulus@switch:~$ ifreload -a

Drop Untagged Frames

With VLAN-aware bridge mode, you can configure a switch port to drop any untagged frames. To do this, add bridge-allow-untagged no to the switch port (not to the bridge). The bridge port is without a PVID and drops untagged packets.

The following example command configures swp2 to drop untagged frames:

cumulus@switch:~$ net add interface swp2 bridge allow-untagged no
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit 
cumulus@switch:~$ nv set interface swp2 bridge domain br_default untagged none
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file to add the bridge-allow-untagged no line under the switch port interface stanza, then run the ifreload -a command.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1

auto swp2
iface swp2
    bridge-allow-untagged no

auto br_default
iface br_default
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 20
    bridge-vlan-aware yes
...
cumulus@switch:~$ sudo ifreload -a

When you check VLAN membership for that port, it shows that there is no untagged VLAN.

cumulus@switch:~$ bridge -c vlan show
portvlan ids
swp1 1 PVID Egress Untagged
  10 20

swp2 10 20

bridge 1

VLAN Layer 3 Addressing

When configuring the VLAN attributes for the bridge, specify the attributes for each VLAN interface. If you are configuring the switch virtual interface (SVI) for the native VLAN, you must declare the native VLAN and specify its IP address. Specifying the IP address in the bridge stanza itself returns an error.

The following example commands declare native VLAN 10 with IPv4 address 10.1.10.2/24 and IPv6 address 2001:db8::1/32.

The NVUE and Linux commands also show an example with multiple VLAN-aware bridges.

cumulus@switch:~$ net add vlan 10 ip address 10.1.10.2/24
cumulus@switch:~$ net add vlan 10 ipv6 address 2001:db8::1/32
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ nv set interface vlan10 ip address 10.1.10.2/24
cumulus@switch:~$ nv set interface vlan10 ip address 2001:db8::1/32
cumulus@switch:~$ nv config apply
cumulus@switch:~$ nv set interface bridge2_vlan10 type svi
cumulus@switch:~$ nv set interface bridge2_vlan10 vlan 10
cumulus@switch:~$ nv set interface bridge2_vlan10 base-interface bridge2
cumulus@switch:~$ nv set interface bridge2_vlan10 ip address 10.1.10.2/24
cumulus@switch:~$ nv set interface bridge1_vlan10 type svi
cumulus@switch:~$ nv set interface bridge1_vlan10 vlan 10
cumulus@switch:~$ nv set interface bridge1_vlan10 base-interface bridge1
cumulus@switch:~$ nv set interface bridge1_vlan10 ip address 12.1.10.2/24
cumulus@switch:~$ nv config apply

Edit the /etc/network/interfaces file, then run the ifreload -a command.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 20
    bridge-vlan-aware yes

auto vlan10 iface vlan10 address 10.1.10.2/24 address 2001:db8::1/32 vlan-id 10 vlan-raw-device br_default

cumulus@switch:~$ ifreload -a

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge2_vlan10
iface bridge2_vlan10
    address 10.1.10.2/24
    hwaddress 1c:34:da:1d:e6:fd
    vlan-raw-device bridge2
    vlan-id 10

auto bridge1_vlan10 iface bridge1_vlan10 address 12.1.10.2/24 hwaddress 1c:34:da:1d:e6:fd vlan-raw-device bridge1 vlan-id 10

The first time you configure a switch, all southbound bridge ports are down; therefore, by default, the SVI is also down. You can force the SVI to always be up by disabling interface state tracking so that the SVI is always in the UP state, even if all member ports are down. Other implementations describe this feature as no autostate. This is beneficial if you want to perform connectivity testing.

To keep the SVI perpetually UP, create a dummy interface, then make the dummy interface a member of the bridge.

Example Configuration

By default, Cumulus Linux automatically generates IPv6 link-local addresses on VLAN interfaces. If you want to use a different mechanism to assign link-local addresses, you can disable this feature. You can disable link-local automatic address generation for both regular IPv6 addresses and address-virtual (macvlan) addresses.

To disable automatic address generation for a regular IPv6 address on a VLAN, run the following command. The following example command disables automatic address generation for a regular IPv6 address on VLAN 10.

cumulus@switch:~$ net add vlan 10 ipv6-addrgen off
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
NVUE commands are not supported.

Edit the /etc/network/interfaces file to add the line ipv6-addrgen off to the VLAN stanza, then run the ifreload -a command.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vlan10
iface vlan 10
    ipv6-addrgen off
    vlan-id 10
    vlan-raw-device br_default
...
cumulus@switch:~$ ifreload -a

To reenable automatic link-local address generation for a VLAN:

cumulus@switch:~$ net del vlan 10 ipv6-addrgen off
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
NVUE commands are not supported.
Edit the /etc/network/interfaces file to remove the line ipv6-addrgen off from the VLAN stanza, then run the ifreload -a command.

Static MAC Address Entries

You can add a static MAC address entry to the layer 2 table for an interface within the VLAN-aware bridge by running a command similar to the following:

cumulus@switch:~$ sudo bridge fdb add 12:34:56:12:34:56 dev swp1 vlan 150 master static
cumulus@switch:~$ sudo bridge fdb show
44:38:39:00:00:7c dev swp1 master bridge permanent
12:34:56:12:34:56 dev swp1 vlan 150 master bridge static
44:38:39:00:00:7c dev swp1 self permanent
12:12:12:12:12:12 dev swp1 self permanent
12:34:12:34:12:34 dev swp1 self permanent
12:34:56:12:34:56 dev swp1 self permanent
12:34:12:34:12:34 dev bridge master bridge permanent
44:38:39:00:00:7c dev bridge vlan 500 master bridge permanent
12:12:12:12:12:12 dev bridge master bridge permanent

Example Configuration

The following example configuration contains a pruned access port and switch port; the ports only send and receive traffic tagged to and from a specific set of VLANs that the bridge-vids attribute specifies. The example also contains other switch ports that send and receive traffic from all the defined VLANs.

...
# ports swp3-swp48 are trunk ports which inherit vlans from the 'bridge'
# ie vlans 310,700,707,712,850,910
#
auto br_default
iface br_default
      bridge-ports swp1 swp2 swp3 ... swp51 swp52
      bridge-vids 310 700 707 712 850 910
      bridge-vlan-aware yes
auto swp1
iface swp1
      bridge-access 310
      mstpctl-bpduguard yes
      mstpctl-portadminedge yes
# The following is a trunk port that is "pruned".
# native vlan is 1, but only .1q tags of 707, 712, 850 are
# sent and received
#
auto swp2
iface swp2
      mstpctl-bpduguard yes
      mstpctl-portadminedge yes
      bridge-vids 707 712 850
# The following port is the trunk uplink and inherits all vlans
# from 'bridge'; bridge assurance is enabled using 'portnetwork' attribute
auto swp49
iface swp49
      mstpctl-portnetwork yes
      mstpctl-portpathcost 10
# The following port is the trunk uplink and inherits all vlans
# from 'br_default'; bridge assurance is enabled using 'portnetwork' attribute
 auto swp50
 iface swp50
      mstpctl-portnetwork yes
      mstpctl-portpathcost 0
...

Considerations

Spanning Tree Protocol (STP)

VLAN Translation

You cannot enable VLAN translation on a bridge in VLAN-aware mode. Only traditional mode bridges support VLAN translation.

Bridge Conversion

You cannot convert traditional mode bridges automatically to and from a VLAN-aware bridge. You must delete the original configuration and bring down all member switch ports before creating a new bridge.