OMP route redistribution | Overlay Management Protocol | Cisco Catalyst SD-WAN Routing Configuration Guide, Releases 26.x and Later

Details which protocols are automatically redistributed into OMP (like Static and Connected) and which require explicit configuration (like BGP and EIGRP).

OMP route redistribution determines which routes OMP automatically learns and advertises, and which routes require explicit configuration for redistribution to prevent routing issues.

OMP automatically redistributes these routes after learning it either locally or from its routing peers:

Connected
Static
OSPF intra-area routes
OSPF inter-area routes
OSPFv3 intra-area routes (Address-Family IPv6)
OSPFv3 inter-area routes (Address-Family IPv6)

To avoid routing loops and less than optimal routing, redistribution of these routes require explicit configuration:

BGP
EIGRP
LISP
IS-IS
OSPF external routes
OSPFv3 external route (Address-Family IPv6)
OSPFv3 all routes (Address-Family IPv4)

Advertise network

The advertise network <ipv4-prefix> command advertises a specific prefix when a non-OMP route corresponding to the prefix is present in the VRF IPv4 routing table.

Note

This command is only supported for address-family ipv4 .

This is an example for advertise network configuration:

omp
  no shutdown
  graceful-restart
  address-family ipv4 vrf 1
   advertise connected
   advertise static
   advertise network X.X.X.X/X
  !

To avoid propagating excessive routing information from the edge to the access portion of the network, the routes that devices receive via OMP are not automatically redistributed into the other routing protocols running on the routers. If you want to redistribute the routes received via OMP, you must enable this redistribution locally on each device.

OMP route origin type and sub-type

OMP sets the origin and sub-origin type in each OMP route to indicate the route's origin. The Cisco Catalyst SD-WAN Controller and the router consider the origin type and subtype when selecting routes.


OMP route origin type	OMP route origin subtype
BGP	External Internal
Connected	—
OSPF	Intra-area, Inter-area, External-1, External-2, NSSA-External-1 and NSSA-External-2
OSPFv3	Intra-area, Inter-area, External-1, External-2, NSSA-External-1 and NSSA-External-2
Static	—
EIGRP	EIGRP Summary EIGRP Internal EIGRP External
LISP	—
IS-IS	Level 1 and level 2

OMP also carries the metric of the original route. A metric of 0 indicates a connected route.

Prior to Cisco Catalyst SD-WAN Manager Release 26.2.1, you could associate a route-map under the OMP configuration for protocol redistribution even if the route-map was not defined. In such cases, the association was effectively a no-operation because the route-map itself did not exist.

Starting from Cisco Catalyst SD-WAN Manager Release 26.2.1, validation check is introduced that requires the route-map to be defined before it can be associated under the OMP configuration. This means you must first create the route-map and then associate it with the OMP configuration for protocol redistribution.

vm41(config)# sdwan omp address-family ipv4 vrf 10
vm41(config-vrf-10)# advertise bgp route-map test
vm41(config-vrf-10)# commit

The route-map named test is defined prior to the association; otherwise, the configuration is not accepted. This behavior ensures configuration correctness to prevent silent no-operation associations of undefined route-maps under OMP redistribution settings.

Configure the redistribution of OSPF routes using CLI commands

Configure the redistribution of OSPF routes into OMP for VRF1.

Procedure

Configure advertise ospf route-map <route-map-name> external .

The OSPF internal routes are redistributed into OMP by default without any explicit configuration.

Example:

This example shows the redistribution of OSPF external routes on all VRFs:

omp      
  no shutdown
  ecmp-limit       6
  graceful-restart
  no as-dot-notation
  timers  
   holdtime               300
   graceful-restart-timer 120
  exit    
  address-family ipv4
   advertise ospf external <-- This configuration implies OSPF Inter-Area/Intra-Area routes & External routes are redistributed into OMP
   advertise connected
   advertise static
  !

The following example shows the redistribution of OSPF external routes for a specific VRF:

Example:

omp      
  no shutdown
  ecmp-limit       6
  graceful-restart
  no as-dot-notation
  timers  
   holdtime               300
   graceful-restart-timer 120
  exit    
  address-family ipv4 vrf 1
   advertise ospf external
   advertise ospf route-map RLB
  !

Use the external keyword in the configuration to apply the supplied route-map to both external and internal OSPF routes (Intra-Area/Inter-Area).
Example:

This example shows the redistribution of OSPFv3 external routes:
```
omp      
  no shutdown
  ecmp-limit       6
  graceful-restart
  no as-dot-notation
  timers  
   holdtime               300
   graceful-restart-timer 120
  exit    
   address-family ipv6  
   advertise ospfv3
   advertise ospf external
  
  !
```
Starting from Cisco IOS XE Catalyst SD-WAN Release 17.7.2, the real-time display of omp routes received and advertised in SD-WAN Manager are limited to only 4001 routes to avoid excessive CPU usage.

Administrative distance

Administrative distance is a metric that

is used to select the best path when there are two or more different routes to the same destination from multiple routing protocols, and
is used by Cisco Catalyst SD-WAN Controller or the router to prefer the OMP route to a destination with the lowest administrative distance value.

This table lists the default administrative distances used by the Cisco IOS XE Catalyst SD-WAN devices:


Protocol	Administrative distance
Connected	0
Static	1
NAT (NAT and static routes cannot coexist in the same VPN; NAT overwrites static routes)	1
Learned from DHCP	1
EIGRP Summary	5
EBGP	20
EIGRP	Internal: 90, External: 170
OSPF	110
OSPFv3	110
IS-IS	115
IBGP	200
OMP	251

OMP best path algorithm

Cisco IOS XE Catalyst SD-WAN devices advertise their local paths to the Cisco Catalyst SD-WAN Controller using OMP. Depending on the network topology, some paths might be advertised from multiple devices.

Cisco IOS XE Catalyst SD-WAN devices use this algorithm to choose the best path:

Table 1. Best path algorithm
Step	Applies to	Description
1	Edge devices Cisco Catalyst SD-WAN Controller	Path validity Checks whether the OMP path is valid. If not, ignores it.
2	Edge devices Cisco Catalyst SD-WAN Controller	Active vs. stale paths Prefers an active path over a stale path. An active path is the one from a peer with which an OMP session is up. A stale path is one from a peer with which an OMP session is in Graceful Restart mode. Note A stale path is only advertised if the stale version is similar to the Route Information Base (RIB) version. Otherwise, the stale path is dropped.
3	Edge devices	Administrative distance Selects the OMP path with the lower administrative distance. Example: A path that the device learns locally via BGP would be preferred over a path that it learns from a Cisco Catalyst SD-WAN Controller via OMP. For information about administrative distance, see Administrative distance.
4	Edge devices Cisco Catalyst SD-WAN Controller	OMP path preference Selects the OMP path with the higher OMP path preference value.
5	Cisco Catalyst SD-WAN Controller	Access region Cisco Catalyst SD-WAN Controller drops advertisement from border router (BR) to BR in the same region.
6	Edge devices	Core region Cisco Catalyst SD-WAN Controller allows advertisement between BRs in the same access region, but receives BR drops advertisement.
7	Multi-Region Fabric scenario only Edge devices	Region path length Compares region-path-length and prefers lower. If region-path-length-ignore is configured, then skips this step. (This addresses secondary regions in Multi-Region Fabric.)
8	Multi-Region Fabric scenario only Border routers	Access region vs. core region Prefers access region paths over core region paths.
9	Edge devices	Direct vs. transport gateway path Prefers a direct path over a transport gateway path. This step can be modified by the transport gateway path preference options, which can (a) cause the transport gateway path to be preferred, or (b) result in the paths to be considered equal. See Configure the Transport Gateway Path Preference in the Cisco Catalyst SD-WAN Multi-Region Fabric (also Hierarchical SD-WAN) Configuration Guide.
10	Multi-Region Fabric scenario only Edge devices	Multi-Region Fabric subregion comparison Prefers paths from the router's own subregion. When comparing two paths that are not from the router's subregion, prefers a path that is not part of any subregion.
11	Multi-Region Fabric scenario only Edge devices	Border router preference Prefers a path with a higher border router preference value.
12	Edge devices	Derived affinity Prefers a path with a lower derived affinity value.
13	Edge devices with an affinity preference configured	Affinity preference Depending on the affinity preference configured on the device, prefers a path whose affinity is earlier in the preference list (higher priority). If the device uses affinity-preference-auto, then it prefers a path with a numerically lower affinity group. Note When comparing two paths with similar reorigination types, one with an affinity value and one without, prefers the path with an affinity value.
14	Edge devices	TLOC preference Select an OMP path with a higher TLOC preference value. Note With TLOC preference and AAR policy configured, outbound and inbound traffic may follow different paths when the preferred TLOC goes out of SLA. For outbound traffic, tunnels in SLA will be preferred regardless of TLOC preference; however, TLOC preference still dictates inbound path selection.
15	Edge devices Cisco Catalyst SD-WAN Controller	Origin type and subtype Compares the origin type and subtype, and selects the first match from this list: Connected Static EIGRP Summary BGP External EIGRP Internal OSPF/OSPFv3 Intra-area OSPF/OSPFv3 Inter-area IS-IS Level 1 EIGRP External OSPF/OSPFv3 External (External OSPF Type1 is preferred over External OSPF Type2) IS-IS Level 2 BGP Internal Unknown
16	Edge devices Cisco Catalyst SD-WAN Controller	Origin metric Selects an OMP path that has a lower origin metric.
17	Cisco Catalyst SD-WAN Controller	Path source Prefers a path sourced from an edge router over the same path coming from a Cisco Catalyst SD-WAN Controller.
18	Edge devices Cisco Catalyst SD-WAN Controller	Private IP address If the router IDs are equal, a Cisco IOS XE Catalyst SD-WAN device selects the OMP path with the lower private IP address. If a Cisco Catalyst SD-WAN Controller receives the same prefix from two different sites and if all attributes are equal, it chooses both of them.

Note

From all equal cost multi-paths for a given prefix that are selected as best-paths and accepted by policy, advertise no more than the number of paths specified in send-path-limit.

Choosing the best path

Examples for choosing the best path:

Control connection failover and route advertisement

In a setup with two WAN Edge devices and four Cisco SD-WAN Controllers:

WAN Edge 1 forms control connections with two controllers by default (e.g., Controller 1 and Controller 2). If one of these controllers fails (e.g., Controller 1), WAN Edge 1 automatically reconnects to a backup controller (e.g., Controller 3) while maintaining its session with Controller 2.

After failover, route advertisements may change. If WAN Edge 2 originates prefix A and is connected to Controller 2, Controller 2 may not advertise prefix A to WAN Edge 1 if WAN Edge 1 now learns this prefix through Controller 3.

Thus, WAN Edge 1 only receives prefix A from Controller 3.

Day 1 Expected Behavior: A Cisco SD-WAN Controller does not re-advertise a route learned from another Cisco SD-WAN Controllerto a WAN Edge device if that device already receives the same route directly from a Cisco SD-WAN Controller.

However, this behavior is not always deterministic. Sometimes, the route may still be advertised, especially after you run the clear sdwan omp all command or disable graceful restart (GR).

Best path selection

When a Cisco SD-WAN Controller receives an OMP path (for example, 10.10.10.0/24) via OMP from a Cisco IOS XE Catalyst SD-WAN device (with an origin code of OSPF) and also from another Controller (with the same origin code), the best-path algorithm selects the path that the Cisco IOS XE Catalyst SD-WAN device sends directly, assuming all other factors are equal.

When a Controller learns the same OMP path (such as 10.10.10.0/24) from two Cisco IOS XE Catalyst SD-WAN devices at the same site, it chooses both paths and advertises them to other OMP peers, as long as all parameters are equal. By default, the Controller advertises up to four equal-cost paths.

Note

A Cisco IOS XE Catalyst SD-WAN device installs an OMP path in its forwarding table (FIB) only if the TLOC to which it points is active. For a TLOC to be active, an active BFD session must be associated with that TLOC. BFD sessions are established by each device which creates a separate BFD session with each of the remote TLOCs. If a BFD session becomes inactive, the Cisco SD-WAN Controller removes from the forwarding table all the OMP paths that point to that TLOC.