Extract from:
UPDATED: High AvailabilityHigh Availability or redundancy can be achieved by running a backup network cable parallel to the Wanos device. When running RSTP the Wanos Core device is placed between two switches, connected via wan0 to the outside switch and lan0 to the inside switch. The backup link is cabled between the same two switches. RSTP should elect the primary and secondary path based on the port id. Ensure the Wanos link is on the lower port number or configure the switch to make this link the primary path. RSTP should place the backup link in an alternative path status and will switch over to the backup link within a few milliseconds of detecting a loss.
When running Per-Vlan RSTP high availability can be achieved using a single switch. In this case two VLAN's are created. The Outside VLAN connects the WAN segment and the Inside VLAN connects the LAN segment. In the diagram below, the Router, Wanos wan0 and the backup link is connected to VLAN 10. On the LAN side the Wanos lan0, Data LAN segment and the backup link is connected to VLAN 20. Under normal conditions the Wanos device bridge traffic between the two segments and the backup link is passively idling. When the switch detects a failure on the primary path, the backup link is enabled and immediately placed in the forwarding state. Advance features like loop guard and hello timers can be adjusted to improve convergence times.
Example Cisco Switch Config:
spanning-tree mode rapid-pvst
interface fa0/1
description WAN-Router
switchport access vlan 10
spanning-tree mode access
interface fa0/2
description Cross-over-fa0/5
switchport access vlan 10
spanning-tree mode access
interface fa0/3
description Wanos-wan0
switchport access vlan 10
spanning-tree mode access
interface fa0/4
description Wanos-lan0
switchport access vlan 20
spanning-tree mode access
! Primary Link via Wanos lan0
spanning-tree cost 1
interface fa0/5
description Cross-over-fa0/2
switchport access vlan 20
spanning-tree mode access
interface range fa0/6 -24
description LAN
switchport access vlan 20
spanning-tree mode accessExample diagram of enabling redundancy with a single switch: