Exam 350-401 topic 1 question 430 discussion

The answer C is correct. ref: book Cisco Software-Defined Wide Area Networks Chapter OMP routes, page 48–51 TLOC: The Transport Location (TLOC) identifier is the next hop of the OMP route. This attribute is very similar to the BGP_NEXT_HOP attribute. Within the TLOC, there are three values:

TLOC for the overlay acts as IP next hop for the underlay: https://www.networkacademy.io/ccie-enterprise/sdwan/underlay-vs-overlay-routing

Correct Answer is A. TLOC serves as an identifier for a tunnel, not just a "next hop" in routing. While TLOCs may indirectly affect routing, their primary function is to uniquely identify and manage tunnels in the SD-WAN overlay network.

The correct answer is obviously A.

TLOCs (Transport Locators) are exchanged between WAN Edge routers to establish overlay tunnels, but TLOCs alone do not specify a particular tunnel. Instead, they represent the endpoints or locations over which tunnels can be established.

C is more accurate In cisco SD-WAN overlay the ackets are forwarded between overlay nodes over IPsec tunnels. Next-hop is a TLOC of a remote peer. https://www.networkacademy.io/ccie-enterprise/sdwan/underlay-vs-overlay-routing#:~:text=Packets%20are%20forwarded%20between%20overlay%20nodes%20over%20IPsec%20tunnels.%20Next%2Dhop%20is%20a%20TLOC%20of%20a%20remote%20peer https://carpe-dmvpn.com/2019/12/14/tlocs-cisco-sd-wan/#:~:text=If%20a%20route,as%20an%20example. .................

C is more accurate than A

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Good contribution from everyone. THX

OMP Routes VPN: Every OMP route is associated with a VPN, and every Cisco SD-WAN device keeps a separate routing table for each VPN. ... Originator: This is the System-IP of the router, from which the route was originally learned from. ... TLOC: This is the next-hop identifier of the OMP route.

TLOC: This is the transport location identifier of the next hop for OMP routes. It is similar to the BGP NEXT_HOP attribute. CCNP Enterprise Design ENSLD 300-420 Official Cert Guide page 353

Looks like A and C are technically correct. At least based on the following documentation: Choose what you will, I chose A based on this information but C looks correct too. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/routing/ios-xe-17/routing-book-xe/m-unicast-routing.html "Configure the Number of Advertised Routes A Cisco IOS XE SD-WAN device can have up to eight WAN interfaces, and each WAN interface has a different TLOC (...) that is configured as a tunnel interface. (...) This means that each router can have up to eight TLOCs. The device advertises each route–TLOC tuple to the Cisco vSmart Controller." "OMP Route Advertisements (...), OMP advertises to its peers the routes and services that it has learned from its local site, along with their corresponding transport location mappings, which are called TLOCs. These routes are called OMP routes or vRoutes to distinguish them from standard IP routes. T(...)."

"Put simply, TLOCs are data plane setup instructions sent by each WAN Edge to the vSmart. The vSmart then distributes the maps to the other WAN Edge routers per the topology policy, facilitating the data plane tunnel establishment." https://carpe-dmvpn.com/2019/12/14/tlocs-cisco-sd-wan/ So that I will go to answer A.

"TLOCs serve another important function besides data plane connectivity. In OMP terms (the routing protocol used over the SD-WAN Fabric), the TLOC serves as a next-hop for route advertisements."

OMP Routes, also referred to as vRoutes, are prefixes learned at the local site via connected interfaces, static routes, and dynamic routing protocols (such as OSPF, EIGRP, and BGP) running on the service side of the vEdge. These prefixes are redistributed into OMP and advertised to the vSmart controller so that they can be carried across the overlay fabric to all other WAN edge nodes. OMP routes resolve their next-hop to a TLOC. An OMP route is installed in the forwarding table only if the next-hop TLOC is known and there is a BFD session in UP state associated with that TLOC;

According to the official Cisco SD-WAN book: "TLOCs are what identify the WAN Edge to the physical underlay" Meaning Answer A would be wrong because it says "SD-WAN overlay" I would go with answer C

A TLOC is a Cisco WAN Edge devicea Transport Locator that represents an attachment point where connects to a WAN transport. A TLOC is uniquely identified by a tuple of three values - (System-IP address, Color, Encapsulation) A TLOC route consists of all required information needed by a remote peer in order to establish an overlay tunnel with that TLOC. This includes private and public IP addresses and ports, site-id, preference, weight, status, encapsulation info such as encryption and authentication parameters, and much more.