SDWAN TLOC Extensions

SDWAN TLOC Extensions

The ideal scenario is that every WAN Edge router is multi-homed and directly connected to every transport provider. Cisco SD-WAN overlay tunnels are built through all directly connected transports.

During a circuit failure, both edge routers maintain WAN connectivity to at least one transport provider. During a transport failure, both edge routers maintain WAN connectivity to the remaining transport provider. In case of a router failure, the remaining edge router maintains connectivity to both transport providers.

At times WAN Edge routers cannot be connected to each transport directly, and only one WAN Edge router can be connected to a single transport. Alternatively, a switch can be connected to each transport, and the Cisco SD-WAN routers can connect to each transport through the connected switches. Such topology is not usually recommended at a branch because it adds cost to the solution and results in having another device to manage.

TLOC extensions allow each WAN Edge router to access the opposite transport through a TLOC-extension interface on the neighboring WAN Edge router.

In the figure, WAN Edge 1 connects directly to the MPLS transport and uses the TLOC extension interface on WAN Edge 2 to connect to the internet transport. In turn, WAN Edge 2 connects directly to the internet transport and uses the TLOC extension interface on WAN Edge 1 to connect to the MPLS transport. The connection from a TLOC extension interface through to transport is transparent. WAN Edge 1 router in the diagram still has two physical interfaces with tunnels configured – one to the MPLS and one to the internet and is unaware that the tunnel to the internet passes through another Cisco SD-WAN router.