Routing Configuration Guide, Cisco Catalyst SD-WAN Releases 17.x

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Hub-and-Spoke connectivity example

Updated: February 6, 2026

Overview

Provides details about the changes in network connectivity when converting a full-mesh environment into a centralized architecture. Reviewing this scenario helps you visualize how BFD sessions and route advertisements are modified to ensure that spokes communicate exclusively through the designated hub router.

This section provides a detailed example demonstrating how network connectivity changes when a full-mesh network is converted to a hub-and-spoke topology.

The following table details the devices, their intended roles, IP addresses, interfaces, and prefixes used in this example, along with their corresponding color coding for illustrations.

Table 1. Devices, IP Addresses, Roles, Interfaces, and Prefixes

Device

Intended Role

Interfaces

Prefixes

Device0

172.16.255.15

Color in illustration: Purple

Hub

10.0.20.15 (3g)

10.1.15.15 (LTE)

None

Device1

172.16.255.35

Color in illustration: Green

Spoke1

10.5.1.35 (LTE)

10.20.35.0/24

Color in illustration: Green highlight

Device2

172.16.255.45

Color in illustration: Blue

Spoke2

10.0.6.45 (LTE)

10.20.45.0/24

Color in illustration: Blue highlight

SDWAN-Controller09

172.16.255.19

Color in illustration: Dark red

Cisco SD-WAN Controller

Not applicable

Not applicable

SDWAN-Controller10

172.16.255.20

Color in illustration: Red

Cisco SD-WAN Controller

Not applicable

Not applicable

The following figure shows the initial state of the network, with full-mesh connectivity before configuring hub-and-spoke.

Figure 1. Network Connectivity Before Hub-and-Spoke Configuration

The following figure shows the network connectivity after configuring hub-and-spoke.

Figure 2. Network Connectivity After Hub-and-Spoke Configuration

Device0 (Hub) connectivity before and after

This section details the observed connectivity for Device0, which functions as the hub, both before and after the hub-and-spoke configuration. It includes information regarding BFD sessions, OMP routes, and IP routes.

BFD Sessions on Device0 (Hub)

The following describes the state of BFD sessions on Device0.

  • Before Configuration: The show sdwan bfd sessions command shows that it has BFD sessions with both Device1 (Spoke1) and Device2 (Spoke1).

  • After configuration: Device0 retains the same BFD sessions with both Device1 (Spoke1) and Device2 (Spoke2).

Figure 1. Hub: BFD Sessions Before and After

OMP Routes on Device0 (Hub)

The following describes the state of OMP routes on Device0.

  • Before Configuration: The show sdwan omp route vpn 1 command shows that the prefixes advertised by Device1 (Spoke1) and Device2 (Spoke2) are reachable only through Device1 (Spoke1) and Device2 (Spoke2), respectively.

  • After configuration: The Device1 (Spoke1) prefix and the Device2 (Spoke2) prefix are reachable through the hub itself (indicated by 0.0.0.0 in the FROM PEER column).

Figure 2. Hub: OMP Routes Before and After

IP Routes on Device0 (Hub)

The following describes the state of IP routes on Device0.

  • Before Configuration: The show ip route vrf 1 command shows that the prefixes advertised by Device1 (Spoke1) and Device2 (Spoke2) are reachable through Device1 (Spoke1) and Device2 (Spoke2), respectively.

  • After configuration: This connectivity remains unchanged for Device0.

Figure 3. Hub: IP Routes Before and After

Device1 (Spoke1) connectivity before and after

This section details the observed connectivity for Device1, which functions as Spoke1, both before and after the hub-and-spoke configuration. It includes information regarding BFD sessions, OMP routes, and IP routes.

BFD Sessions on Device1 (Spoke1)

The following describes the state of BFD sessions on Device1.

  • Before Configuration: The show sdwan bfd sessions command shows BFD sessions with both Device0 (future hub) and Device2 (future Spoke2).

  • After configuration: Device1 only has BFD sessions with the hub; there are no BFD sessions with other spokes (for example, Spoke2).

Figure 1. Spoke1: BFD Sessions Before and After

OMP Routes on Device1 (Spoke1)

The following describes the state of OMP routes on Device1.

  • Before Configuration: The show sdwan omp route vpn 1 command shows that it can reach the Device2 (Spoke2) prefix directly through Device2. This is evident because the TLOC IP column shows the system IP of Device2.

  • After configuration: Device1 can reach the Device2 (Spoke2) prefix only through the hub.

Figure 2. Spoke1: OMP Routes Before and After

IP Routes on Device1 (Spoke1)

The following describes the state of IP routes on Device1.

  • Before Configuration: The show ip route vrf 1 command shows Device1 could reach the Device2 prefix directly through Device2.

  • After configuration: Device1 (Spoke1) can reach the Device2 (Spoke2) prefix only through the hub..

Figure 3. Spoke1: IP Routes Before and After

Device2 (Spoke2) connectivity before and after

This section details the observed connectivity for Device2, which functions as Spoke2, both before and after the hub-and-spoke configuration, mirroring the changes observed for Device1. It includes information regarding BFD sessions, OMP routes, and IP routes.

BFD Sessions on Device2 (Spoke2)

The following describes the state of BFD sessions on Device2.

  • Before Configuration: The show sdwan bfd sessions command shows Device2 had BFD sessions with both Device0 (future hub) and Device1 (future Spoke1).

  • After configuration: Device2 only has BFD sessions with the hub; there are no BFD sessions with other spokes (for example, Spoke1).

Figure 1. Spoke2: BFD Sessions Before and After

OMP Routes on Device2 (Spoke2)

The following describes the state of OMP routes on Device2.

  • Before Configuration: The show sdwan omp route vpn 1 command shows that Device2 could reach the Device1 (Spoke1) prefix directly through Device1 (TLOC IP column shows the system IP of Device1).

  • After configuration: Device2 can reach the Device1 (Spoke1) prefix only through the hub.

Figure 2. Spoke2: OMP Routes Before and After

IP Routes on Device2 (Spoke2)

The following describes the state of IP routes on Device2.

  • Before Configuration: The show ip route vrf 1 command shows that Device2 could reach the Device1 prefix directly through Device1.

  • After configuration: Device2 can reach the Device1 (Spoke1) prefix only through the hub.

Figure 3. Spoke2: IP Routes Before and After