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[SDWAN] Overlay Management Protocol (OMP) - Part 2 (English)
Nam Nguyen
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OMP Advertisement
As the example above, the cEdge#1 router uses routes learned from the connected, static and dynamic protocols inside the local network. They will be advertised to all OMP peers (vSmarts) along with the corresponding TLOC next-hops.
In order to understand more about OMP, I will shortly introduce TLOC (Transport Locator) which is a component in Cisco SDWAN network that contains basic information about a WAN connection:
- System-IP
- Transport Color
- Encapsulation Type
- Public/Private IP address and port numbers.
- And some other components
The TLOC contains the information needed for a cEdge to establish tunnels to another cEdges in the SDWAN.
Going back to OMP Advertisement, OMP has the following types of routes:
- TLOC routes
- OMP routes
- Service routes
TLOC routes
As introduced about TLOC above, each WAN transport of each cEdge is identified by a TLOC (System-IP, encaps, color, pubIP, ...).
When cEdge joins SDWAN, cEdge will advertise its TLOC to OMP peers (vSmarts), and by default, vSmart will distribute TLOC routes to other cEdges and vice versa.
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This helps cEdges to know the necessary information within the TLOC and establish tunnels with each other based on this information.
OMP routes
The cEdges in the SDWAN will advertise the prefixes learned from the LAN information via OMP to vSmart peers. These OMP routes are also known as vRoute.
As the example in Figure 2 shows, cEdge#1 contains the static route 192.168.1.0/24, and advertises this prefix to vSmart with the next-hop TLOC-1. When cEdge#3 receives the prefix 192.168.1.0/24 advertised by vSmart, it will update this prefix to cEdge#3's routing table.
TLOC next-hop is similar to the next-hop of a prefix in IGP, when cEdge#3 sends data to 192.168.1.0/24 will send data directly to TLOC-1 (after using the information in TLOC-1 to make an encrypted connection with cEdge#1).
Note that, like BGP, when the next-hop has no connection (invalid next-hop), the vRoute (OMP routes) will also be invalid, and will not be installed to cEdge's routing table when received.
In addition, like BGP, OMP routes (vRoute) also contain many other attributes:
- VPN
- Originator
- TLOC next-hop
- Site ID
- Preference
These attributes are one of the best path selection factors in case there is more than one path to the destination prefix and will be introduced with examples in the next articles.
See you!