What is OMP?

OMP, overlay management protocol, is a TCP based protocol which is responsible for establishing and maintaining the SD-WAN control plane. It helps us exchange routing information, policy information, and also management information between vSmart controllers and the vEdge routers in your network. There is no need to enable this on your vSmart controller as it is enabled by default.

OMP ROUTE ADVERTISEMENTS:

There are 3 types of routes OMP advertises:

TLOCS - Stands for transport locators. A TLOC represents a point in the network a Cisco edge device connects to a wan transport. TLOCs are identified by 3 different values. These 3 values are: System IP (Think of this as similar to a Router-ID in a routing protocol), transport color which identifies what type of WAN transport is being used and an encapsulation type, either IPsec or GRE. One important thing to know for a successful TLOC route to be formed both sides must use the same encryption type.

OMP Routes (vRoutes) - Prefix that creates connectivity between two end points using OMP orchestrated transport. This could represent services in a data center, services at branch locations, or also a collection of hosts in any location of the overlay network. These routes require and resolve into TLOCs to be able to perform functional forwarding. A good comparison to think of this would be the prefixed carried in any BGP address family indicator.

Service Routes - This type of route ties an OMP route to a service in the network and specifies where the service is at in the network. When I say service I am talking about things such as load balancers, firewalls, IDS, IPS, etc.

I may go deeper on some of these in the future because there is a lot of information. This is just touching the service, but, the last topic I want to talk about is OMP graceful restart and route redistribution. Route redistribution in OMP is pretty simple. By default OMP will automatically redistribute the following routes: connected, static, OPSF intra and inter-area routes. However, for BGP and OSPF external routes you will need to configure these yourselves by enabling it locally on the device. OMP will also carry the metric of the original route and the administrative distance is a little bit different then traditional networking.

OMP Graceful restart is a helpful feature that allows the data plane in the Cisco SD-WAN overlay network to be able to continue functioning if the control plane becomes unavailable. This means if the vSmart controller goes down, Cisco vEdge devices can still continue forwarding data traffic by using the last known good information they had from the vSmart controller. Once the vSmart controller is available again another DTLS connection to the vSmart controller is established and then the device gets updated network information.