Cisco Viptela SDWAN: OMP Graceful Restart !

Today I am going to talk about the Cisco Viptela overlay feature named as Graceful restart for OMP. As you know that OMP stands for Overlay Management protocol and is used to share the L3 routes between vEdge and vSmart. In this article we will discuss the purpose of the Graceful restart for OMP.

So when we are using Graceful restart for the OMP peers?
Graceful restart used in two cases, one if vEdge is down and its peer vSmart takes the last good configuration of that vEdge and continue sending the L3 routes to the other vEdges which are peer to the vSmart.

Fig 1.1- vManage Login Screen

Other if vSmart down, the its peer vEdge router continues to forward the traffic to the desired destination.
So the purpose of the Graceful restart is that it allows OMP peers continue operating if one of the vSmart/vEdge is unavailable may with due to some reason as a peer.

Check the value of graceful restart on the template as well 
Go to Configuration--> template ---> OMP and you will see the below screen as : 

Fig 1.2- OMP graceful Restart on Templates

When this feature is enable, vSmart and vEdge in the peer cache the OMP information that they learn from its peer in order for traffic flow in the SDWAN fabric. The information which is part of the OMP is as below
  1. OMP routes
  2. TLOC routes
  3. Service routes
  4. Centralized data policies
  5. IPsec SA parameters

Note⭐ : Graceful restart for OMP protocol is enabled by default between the peers vSmart and vEdge and the restart time is 12 hours but can be increased up to 7 days.

   Enabling Graceful Restart timer

    Disabling Graceful Restart timer

     Different states with when vSmart is up and other is using graceful restart

Let us suppose if we faced an issue like if vSmart is down and vEdge is rebooted anyhow the cache information in the vEdge will be lost and will not able to forward traffic as vSmart is down as well. 

So make sure to understand if there is any issue with the vSmart don't try to reboot the vEdge as you will not recovered the cache information until and unless vSmart will be backed in the control plane traffic.