SD WAN question - single transport on each router

[carl_townshend]

Hi all

I am currently doing the Cisco SDWAN course and have a question,

If you have say 2 branch routers, running VRRP and 1 of them is the active router, also each router only has 1 active transport, say router 1 connects to MPLS, router 2 connects to the internet.

When traffic goes to the active router 1, how does it reach the internet? do you have to configure a routing protocol using a service template between them? or does it use TLOC extensions to get from router 1 to router 2?

where would you configure this?

[liviu.gheorghe]

Hello @carl_townshend ,

Yes, TLOC extension is a feature that allows a WAN Edge router to communicate over the WAN transport connected to the adjacent WAN Edge router through a TLOC-extension interface.

  See the following link for details on configuration.

https://www.networkacademy.io/ccie-enterprise/sdwan/tloc-extension

[carl_townshend]

How does it handle routing to the internet if say router 1 in the branch is active from a lan side and the internet is only connected to router 2?

[liviu.gheorghe]

Look at the document in the link at the section Configuring TLOC Extensions, Routing Considerations regarding your question.

[Kanan Huseynli]

Hi,

you can do both option, actually : service-side routing configuration or TLOC extension.

I'd go with TLOC extension, because if you lose MPLS, you can still manage MPLS circuit connected router (directly connected) via TLOC extention over internet transport. You have control connection redundancy.

But on the other hand, on data plane side, you will have double transports, thus more BFD sessions with remote sites. And any centralized control/data policy should also include these "new" transports as well.

Regarding routing in case of TLOC extension, I believe it is described in provided document, but let me shortly describe here as well:

Basically, router A (MPLS connected) has inter-connection to router B (Internet connected) via interface which is in VPN0. On router A, you should have additional default route towards router B. On router B you need to have 1:1 static NAT configuration, so interconnection private IP can be mapped to public IP.

Don't forget NAT on router A as well for internet based transport, otherwise you will have reverse route problem.