SVLAN

How to implement an SVLAN to capture all traffic not dealt with locally. For instance, a switch port faces a router with OSPF configured to operate in a VLAN. All other traffic on this switch port should be placed into an SVLAN which is accessible to other ports.

Worked Example

plan, seam, and wood, are all Mikrotik routers. plan and seam have an OSPF session in VLAN 536. plan and wood have an OSPF session in VLAN 520. The VLAN 206 is present on seam and wood and should be trunked transparently through plan. plan does not need VLAN 206 to be configured. Similarly, seam and wood do not need knowledge of SVLAN 3091.

                    +-------------------+
                    | plan              |
                    +-------------------+
                    |    SVLAN: 3091    |
  trunk VLAN 536    |                   | trunk VLAN 520
  trunk VLAN 206    |                   | trunk VLAN 206
+-------------------+                   +-------------------+
| seam              |                   | wood              |
+-------------------+                   +-------------------+

Create the SVLAN on plan. Under ‘Interfaces, VLAN’, create the new VLAN. Name the VLAN, set the VLAN ID, and select the router’s single bridge as the interface. Do not tick ‘Use Service Tag’.

VLANs 520 and 536 already exist on plan for the OSPF sessions with seam and wood. Under ‘Interfaces, VLAN’, select each of the two extant VLANs 520 and 536 and change their interface to the newly created SVLAN. The VLAN list will change to illustrate that VLANs 520 and 536 are now a part of the SVLAN 3091. OSPF will be temporarily disrupted, as the SVLAN 3091 has not been added to a port.

Under ‘Bridge, Ports’, identify the two ports facing seam and wood. Change the PVID on each of these ports to the SVLAN 3091 and ensure that ‘Tag Stacking’ is checked. As long as the physical interfaces are up, under ‘Bridge, VLANs’, it can be seen that the SVLAN 3091 has been dynamically added to these ports by PVID.

Verify that OSPF to seam and wood has been reestablished.

Create VLAN 206 on each of seam and wood, applying it by PVID to any desired access ports, and adding it specifically to the physical uplink to plan under ‘Bridge, VLANs’.

Attach devices to the physical ports on each of seam and plan which are in VLAN 206. Verify connectivity between them by setting IP addresses and pinging across the link. Verify that the MAC addresses of the end devices appear in the MAC address table of seam and wood in VLAN 206, and in the MAC address table of plan in SVLAN 3091, by navigating to ‘Bridge, Hosts’ on each device.

The configuration is complete, and VLAN tagged traffic is passed transparently through plan with no further configuration. Additional configurations now possible are the extension of SVLAN 3091 to other devices by trunking it from plan, and ‘plucking out’ more VLANs from the links to seam and wood, in addition to the OSPF VLANs.