Routing Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x

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Translating OMP metrics for devices outside of the overlay network

Updated: March 9, 2026

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Overview

Describes how transport gateways extend symmetric routing to external LAN devices by translating RIB metrics into BGP or OSPF parameters.

A router configured as a transport gateway and operating as a hub (TGW1 in the illustration below) may conduct traffic between devices within the Cisco Catalyst SD-WAN overlay network (WAN) and a device outside of the overlay network (LAN), such as DC1 in the following illustration. This is WAN-to-LAN traffic. Note that devices outside of the overlay network are not managed by Cisco Catalyst SD-WAN.

A transport gateway translates RIB metric information into parameters used by the BGP or OSPF protocols. It uses those parameters in its BGP or OSPF routing tables, and when the transport gateway advertises routes to its BGP or OSPF neighbors, it includes the RIB-derived parameters with the routes.

These RIB-derived parameters influence path selection by devices in the LAN, helping to ensure that the LAN chooses the same path for LAN-to-WAN traffic as the overlay network uses for WAN-to-LAN traffic.

Figure 1. Translating OMP metrics

Translating OMP metrics to BGP attributes

When you enable a router to translate RIB metrics from OMP to BGP, the router uses the following OMP metric and attribute:

  • OMP route metric

    Among the OMP metrics, one specific metric is named OMP.

  • OMP AS-PATH

The router uses these to derive three BGP attributes:

  • BGP MED

  • BGP LOCAL_PREF

  • BGP AS_PATH

For information about how to view OMP metrics for a route and the resulting BGP attributes, see Monitor RIB metric translation.

Translation from OMP to BGP

Table 1. Translation of OMP metrics to BGP attributes

BGP Attribute

How it is derived
BGP MED Equal to the OMP route metric.
BGP LOCAL_PREF 255 – (OMP route metric)
BGP AS_PATH

Two possibilities:

  • If the propagate-aspath command is used:

    1. If OMP AS-PATH is empty, then the router uses its own local AS value and repeats it (OMP route metric) times, with a maximum of 13 repetitions.

    2. If OMP AS-PATH is not empty, then the router uses the OMP AS-PATH and prepends it with the first AS in the OMP AS-PATH (OMP route metric) times, with a maximum of 13 times.

  • If the propagate-aspath command is not used:

    The router uses a list of its own local AS value, repeated (OMP route metric) times, prepending the value up to a maximum of 13 repetitions.

AS-PATH propagation recommendation

In most scenarios, when you enable translation of RIB metrics using the redistribute omp translate-rib-metric command, also enable propagating the AS-PATH metric using the propagate-aspath command. If you omit this, the router treats the AS-PATH metric as empty.

The router includes these BGP attributes with the routes that it re-originates to a device in a LAN outside the overlay network that uses BGP.

BGP attributes without RIB metric translation

The table below shows combinations of OMP metrics and the BGP attributes that the router derives when RIB metric translation is not enabled.

Table 2. Translation from OMP to BGP without RIB metric translation enabled

OMP metrics:

Example combinations

Translation to BGP attributes:

propagate-aspath enabled

translate-rib-metric not enabled
Example OMP route metric OMP AS-PATH BGP MED BGP LOCAL_PREF BGP AS_PATH
1 0 100 101 1000 50 100 101
2 1 100 101 1 50 100 101
3 2 100 101 2 50 100 101
4 10 (empty) 10 50 (empty)
5 14 100 101 14 50 100 101

Translating OMP metrics to an OSPF metric

If you do not configure the router to translate RIB metrics, it uses a default OSPF metric when it redistributes routes to a device outside the Cisco Catalyst SD-WAN overlay network. The default OSPF metric is 16777214 (hexadecimal FFFFFE).

When you enable the router to translate RIB metrics, it assigns the OMP route metric value as the OSPF metric. For example, if the OMP route metric is 10, the OSPF metric is also 10.

For information about viewing the OMP metrics for a route and the resulting BGP metrics, see Monitor RIB Metric Translation.