VPN to LABEL Mapping on vEdges

[bassomarco1998]

Hello everyone,

I am studying the topic of SD-WAN and I have come across a doubt regarding the mapping between VPN and LABEL. To have the same context, I leave the link of the site from which I am delving into the studies: link.

From this source, it is stated that the VPN-LABEL mapping is local to the router. What is not clear to me, however, is the process by which a vEdge receives a certain route (OMP route) from the Controller (vSmart). In the example on the site, it shows how the vEdges announce the OMP routes along with the LABELs. But when the remote vEdge receives those routes, how does it know that the LABEL assigned to it corresponds to a certain VPN?

If only the controller has the overall view of what the mapping between VPN and LABEL is, how do the other nodes correctly assign the announcements of various routes to the local VPNs?

Thanks in advance to those who will answer.

[balaji.bandi]

OMP routes, or vRoutes, are prefixes that are learned from the local site, or service side, of a WAN Edge router. The prefixes are originated as static or connected routes, or from within the OSPF, BGP, or EIGRP protocol, and redistributed into OMP so they can be carried across the overlay. OMP routes advertise attributes such as transport location (TLOC) information, which is similar to a BGP next-hop IP address for the route, and other attributes such as origin, origin metric, originator, preference, site ID, tag, and VPN. An OMP route is only installed in the forwarding table if the TLOC to which it points is active.

you can find more information below deployment guide :

https://www.cisco.com/c/en/us/td/docs/solutions/CVD/SDWAN/cisco-sdwan-design-guide.html#WANEdgeDeployment

and configuration guide :

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/policies/ios-xe-17/policies-book-xe/service-chaining.html

[Kanan Huseynli · Accepted solution]

Hi,

each OMP route (so called vRoute) has several attributes. Label and VPN-ID are the two main labels that we discuss now. Route with these attributes are advertised from router_A to vsmart and from vsmart to router_B. Receiving router (router_B) understand that prefix belongs to which VPN-ID and on data plane how it should be labelled (MPLS label). This label is important for data plane. Because when router_B sends traffic towards router_A based on previous prefix information, it puts label on data traffic. Router_A will understand how to route traffic on the service side.

Always normal traffic and service-chaining traffic label differs within the same VPN.

Above picture is from CiscoLive (TECTRS-3477).

[MHM Cisco World]

Very Good Q. please dont stop ask like this Q it refresh our info 
NOW which assign Label vSmart or vedge 
the answer in below link which I recommend to check if you study SD-WAN 
the vedge assign label not vSmart  

https://www.networkacademy.io/ccie-enterprise/sdwan/vpns-and-labels

MHM

[MHM Cisco World]

Hi friend sorry it little old post but I review issue in sdwan and see it'

The label is use in vedge is not mpls label it sdwan label' 

Why we need this label?

We have one interface with vpn0 and it receive many traffic toward many service vpn how vpn0 transport know for which vpn this packet is ?

This job of label in fib' it use to forward traffic toward correct vpn.

MHM

[Kanan Huseynli]

SD-WAN Dataplane has MPLS header and label in it. It is exactly MPLS label.

But the purpose is whatever you mentioned. Correctly, route on the service side. Note that, label is not only defines which VPN-ID will be used, but also which service (direct routing or service insertion via FW).

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/security/ios-xe-17/security-book-xe/m-security-overview.html

[MHM Cisco World]

For clear there are two labels here 

1- mpls transport label 

2- service label (send via omp) 

The second one I search and can not totally sure it also called mpls label or not

Maybe you have some ciscolive or doc. You can share I can read it 

Thanks

MHM