Multihoming in a BGP EVPN VXLAN Fabric Configuration Guide, Cisco IOS XE 26.x.x and Later
Multihoming in a BGP EVPN VXLAN Fabric Configuration Guide, Cisco IOS XE 26.x.x and Later
This section provides tasks to configure single-active mode in BGP EVPN VXLAN fabric networks.
Before you configure multihoming in a BGP EVPN VXLAN fabric, ensure that you configure EVPN VXLAN Layer 2 and Layer 3 overlay networks. For detailed steps, refer to the How to Configure EVPN VXLAN Integrated Routing and Bridging section.
This task configures dual-homing with single-active redundancy in a BGP EVPN VXLAN fabric to provide network resilience and prevent traffic loops while ensuring only one path is active at a time.
Dual-homing with single-active redundancy is used in BGP EVPN VXLAN fabrics to provide redundant connectivity where only one of the redundant links is active at any given time, ensuring traffic follows a single path while maintaining backup connectivity.
Perform the following set of procedures to configure dual-homing with single-active redundancy in a BGP EVPN VXLAN fabric. |
Dual-homing with single-active redundancy is configured in the BGP EVPN VXLAN fabric, providing redundant connectivity with loop prevention.
This task migrates a network from a single-homed configuration to a single-active dual-homed configuration to provide redundancy and improved network resilience.
When migrating between topologies, corresponding changes must be made to the Ethernet segment configuration. Failure to make corresponding changes to both the topology and Ethernet segment configuration results in traffic loops and traffic blackholing.
Before you migrate, we recommend that you do not configure the VTEP as the root bridge of the spanning tree, as the provision of Ethernet segment on the interface of a VTEP excludes it from spanning-tree. If the VTEP is the root bridge, its exclusion from the spanning-tree triggers an immediate spanning tree re-convergence.
Follow these steps to migrate from a single-homed topology to a single-active dual-homed topology:
| 1. | Ensure that you do not activate a link between VTEP 2 and a switch in the single-homed network. Activate the second link only once you configure the Ethernet segment. In case a link is already activated, ensure that you deactivate the link. |
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| 2. | Provision the Ethernet segment on the interface of the VTEP that has the active link. Provision of the Ethernet segment updates all the MAC addresses that are locally learned on that interface with the Ethernet segment ID of the interface. |
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| 3. | Provision the Ethernet segment on the interface of the second VTEP that needs to be connected to the switch in the single-homed network. |
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| 4. | Connect the link and bring up the interface of the second VTEP. By doing this, you trigger fast convergence, Ethernet segment auto-discovery, and DF reelection. |
The single-homed network has now migrated to a dual-homed network.
This task enables you to change your network topology from a single-active dual-homed configuration to a single-homed configuration while maintaining network connectivity and avoiding traffic disruptions.
The following figure illustrates the migration from a single-active dual-homed topology to a single-homed topology:
When you migrate from one topology to another, ensure you make corresponding changes to the Ethernet segment configuration. If you change either of the two without making corresponding changes to the other, it results in traffic loops and traffic blackholing.
Ensure that the Ethernet segment remains configured on the dual-homed links as long as the links are up. If the Ethernet segment is removed from an active link, it causes traffic loops.
Follow these steps to migrate from a single-active dual-homed network to a single-homed network:
| 1. | Configure portfast on the link you plan to activate. Before you migrate, we recommended that you configure portfast on the link you activate. Removal of Ethernet segment from an interface on the VTEP puts it back into the spanning-tree. If the interface is not configured with portfast, the port goes through block-learn-forward states and causes extensive traffic loss. |
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| 2. | Shut down the interface that needs to be decommissioned. When you shut down the interface, you trigger fast convergence, Ethernet segment auto-discovery, and DF reelection. As a result, all the traffic converges into the active link. |
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| 3. | Remove the Ethernet segment from the decommissioned interface. Ensure that the interface is down before you disconnect the link. The dual-homed network has now migrated to a single-homed network with an Ethernet segment. |
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| 4. | (Optional) Remove the Ethernet segment from the interface with the active link on the VTEP. Removal of the Ethernet segment updates all the MAC addresses that are locally learned on that interface without the Ethernet segment ID. The Ethernet segment is now removed from the single-homed network homed network. |
You have successfully migrated from a single-active dual-homed topology to a single-homed topology. The network now operates with a single connection path, and all traffic flows through the active link.