Cisco Viptela SDWAN : OMP discussion

You may heard about OMP protocol used in Cisco Viptela SDWAN solution. Lets talk about OMP and what OMP does in Cisco Viptela SDWAN solution

The OMP is implemented between WAN Edge routers and vSmart controllers, as well as between vSmart controllers as a full mesh. It is automatically enabled by DTLS/TLS controls.

A WAN Edge device and a vSmart controller establish a single peering session using their system IPs, regardless of the number of DTLS/TLS connections.

Among the data exchanged between OMP and a provider are route prefixes, next-hop routes, crypto keys, and policy information.

Fig 1.1- OMP

OMP advertise routes:
WAN Edge routers use vRoutes or OMP routes as prefixes that are learned from a local site or service. OMP redistributes the prefixes from OSPF, BGP, or EIGRP protocol or from static or connected routes to carry them across the overlay.

Transport location (TLOC) information, which is similar to a BGP next-hop IP address for the route, as well as origin, origin metric, originator, preference, site ID, tag, and VPN information are advertised in OMP routes.

Note⭐ : TLOCs are only installed in the forwarding table if they point to active OMP routes.

There is also information about TLOC private and public IP addresses, carrier, preference, site ID, tag, weight, and encryption key associated with TLOC routes.

In addition, TLOC routes include private and public IP addresses, carrier preferences, site IDs, tags, weights, and encryption keys.

In the case of equal-cost paths, OMP only advertises the best route or routes.

vSmart controllers should be configured to advertise additional valid paths that don't qualify as the best paths for a given prefix by enabling send-backup-paths OMP parameter.

WAN Edge routers can also make best path decisions based on TLOC availability in addition to improving convergence.

Note⭐ : There are only four equal-cost paths advertised for any given prefix by OMP.

Using dual WAN Edge routers, each connected to two different transports, may not be enough in some designs, since this limit is easily reached.

It is recommended that the send-path-limit OMP parameter for the vSmart controller, or the Number of Paths Advertised per Prefix, is set to 16.

Note⭐ : Both best paths and backup paths are included in the send-path-limit parameter.

WAN Edge routers support the ecmp-limit OMP parameter for increasing this value.