VXLAN active-active mode allows a pair of MLAG switches to act as a single VTEP, providing active-active VXLAN termination for bare metal as well as virtualized workloads.
|VTEP||The virtual tunnel endpoint. This is an encapsulation and decapsulation point for VXLANs.|
|active-active VTEP||A pair of switches acting as a single VTEP.|
|ToR||The top of rack switch; also referred to as a leaf or access switch.|
|spine||The aggregation switch for multiple leafs. Specifically used when a data center is using a Clos network architecture. Read more about spine-leaf architecture in this white paper.|
|exit leaf||A switch dedicated to peering the Clos network to an outside network; also referred to as a border leaf, service leaf, or edge leaf.|
|anycast||An IP address that is advertised from multiple locations. Anycast enables multiple devices to share the same IP address and effectively load balance traffic across them. With VXLAN, anycast is used to share a VTEP IP address between a pair of MLAG switches.|
|RIOT||Routing in and out of tunnels. A Broadcom feature for routing in and out of tunnels. Allows a VXLAN bridge to have a switch VLAN interface associated with it, and traffic to exit a VXLAN into the layer 3 fabric. Also called VXLAN Routing.|
|VXLAN routing||The industry standard term for the ability to route in and out of a VXLAN. Equivalent to the Broadcom RIOT feature.|
|The anycast address for the MLAG pair to share and bind to when MLAG is up and running.|
Configure VXLAN Active-active Mode
VXLAN active-active mode requires the following underlying technologies to work correctly.
|MLAG||Refer to the MLAG chapter for more detailed configuration information. Configurations for the demonstration are provided below.|
|OSPF or BGP||Refer to the OSPF chapter or the BGP chapter for more detailed configuration information. Configurations for the BGP demonstration are provided below.|
|STP||You must enable BPDU filter and BPDU guard in the VXLAN interfaces if STP is enabled in the bridge that is connected to the VXLAN.|
Configurations for the demonstration are provided below.
Active-active VTEP Anycast IP Behavior
You must provision each individual switch within an MLAG pair with a virtual IP address in the form of an anycast IP address for VXLAN data-path termination. The VXLAN termination address is an anycast IP address that you configure as a
clagd parameter (
clagd-vxlan-anycast-ip) under the loopback interface.
clagd dynamically adds and removes this address as the loopback interface address as follows:
- When the switches boot up,
ifupdown2places all VXLAN interfaces in a PROTO_DOWN state. The configured anycast addresses are not configured yet.
- MLAG peering takes place and a successful VXLAN interface consistency check between the switches occurs.
clagd(the daemon responsible for MLAG) adds the anycast address to the loopback interface as a second address. It then changes the local IP address of the VXLAN interface from a unique address to the anycast virtual IP address and puts the interface in an UP state.
In order for the anycast address to activate, you must configure a VXLAN interface on each switch in the MLAG pair.
Failure Scenario Behaviors
|The peer link goes down.|
The primary MLAG switch continues to keep all VXLAN interfaces up with the anycast IP address while the secondary switch brings down all VXLAN interfaces and places them in a PROTO_DOWN state. The secondary MLAG switch removes the anycast IP address from the loopback interface and changes the local IP address of the VXLAN interface to the configured unique IP address.
|One of the switches goes down.|
The other operational switch continues to use the anycast IP address.
All VXLAN interfaces are put in a PROTO_DOWN state. The anycast IP address is removed from the loopback interface and the local IP addresses of the VXLAN interfaces are changed from the anycast IP address to unique non-virtual IP addresses.
|MLAG peering could not be established between the switches.|
|When the peer link goes down but the peer switch is up (the backup link is active).||All VXLAN interfaces are put into a PROTO_DOWN state on the secondary switch.|
|A configuration mismatch between the MLAG switches||The VXLAN interface is placed into a PROTO_DOWN state on the secondary switch.|
Check VXLAN Interface Configuration Consistency
The active-active configuration for a given VXLAN interface must be consistent between the MLAG switches for correct traffic behavior. MLAG ensures that the configuration consistency is met before bringing up the VXLAN interfaces
The consistency checks include:
- The anycast virtual IP address for VXLAN termination must be the same on each pair of switches.
- A VXLAN interface with the same VXLAN ID must be configured and administratively up on both switches.
You can use the
clagctl command to check if any VXLAN switches are in a PROTO_DOWN state.
Configure the Anycast IP Address
With MLAG peering, both switches use an anycast IP address for VXLAN encapsulation and decapsulation. This allows remote VTEPs to learn the host MAC addresses attached to the MLAG switches against one logical VTEP, even though the switches independently encapsulate and decapsulate layer 2 traffic originating from the host. You can configure the anycast address under the loopback interface, as shown below.
Example VXLAN Active-Active Configuration
Note the configuration of the local IP address in the VXLAN interfaces below. They are configured with individual IP addresses, which
clagd changes to anycast upon MLAG peering.
Layer 3 IP Addressing
The IP address configuration for this example:
In this example, the servers are running Ubuntu 14.04. A layer2 bond must be mapped from server01 and server03 to the respective switch. In Ubuntu this is done with subinterfaces.
Using Active-active Mode with LNV
When using VXLAN active-active mode with lightweight network virtualization (LNV), follow the steps outlined above. In addition, the following configuration steps are needed:
- Configuring the loopback interface for active-active mode
- Enabling the registration daemon
- Configuring a VTEP
- Enabling the service node daemon
- Configuring the service node
|The VXLAN registration daemon. The daemon runs on the switch that is mapping VLANs to VXLANs. You must configure the |
|The VXLAN service node daemon that you can run to register multiple VTEPs.|
|The unique IP address to which the |
|The service node anycast IP address in the topology. In this demonstration, this is an anycast IP address shared by both spine switches.|
|anycast||When an IP address is advertised from multiple locations. Allows multiple devices to share the same IP and effectively load balance traffic across them. With VXLAN, anycast is used in two places:|
Configure the Loopback Interface for Active-active Mode
You configure active-active mode as you would for EVPN, as described above, adding two more configuration options to the loopback interface: the
vxrd IP address and the service node IP address.
Continuing with the example configuration above, the loopback interface configuration on the leaf switches would look like this:
Enable the Registration Daemon
You must enable the registration daemon (
vxrd) on each ToR switch acting as a VTEP that is participating in the VXLAN. The daemon is installed by default.
- Open the
/etc/default/vxrdconfiguration file in a text editor.
Enable the daemon, then save the file.
Configure a VTEP
The registration node is already configured in
/etc/network/interfaces; no additional configuration is typically needed. However, you can configure the VTEP in the
/etc/vxrd.conf file instead, which has additional configuration knobs available.
Enable the Service Node Daemon
- Open the
/etc/default/vxsndconfiguration file in a text editor.
Enable the daemon, then save the file:
Restart the daemon.
Configure the Service Node
To configure the service node daemon, edit the
/etc/vxsnd.conf configuration file:
Full configuration of vxsnd.conf
Full configuration of vxsnd.conf
In addition to troubleshooting single-attached configurations, there is now the MLAG daemon (
clagd) to consider. The
clagctl command gives the output of MLAG behavior and any inconsistencies that might arise between a MLAG pair.
The additions to normal MLAG behavior are the following:
|The anycast IP address being shared by the MLAG pair for VTEP termination is in use and is 10.10.10.30.|
|There are no conflicts for this MLAG Interface.|
|The VXLAN is up and running (there is no Proto-Down).|
In the next example the
vxlan-id on VXLAN10 is switched to the wrong
vxlan-id. When the
clagctl command is run, you see that VXLAN10 goes down because this switch is the secondary switch and the peer switch takes control of VXLAN. The reason code is
vxlan-single indicating that there is a
vxlan-id mis-match on VXLAN10.
Caveats and Errata
Use VLAN for Peer Link Only Once
Do not reuse the VLAN used for the peer link layer 3 subinterface for any other interface in the system. A high VLAN ID value is recommended. For more information on VLAN ID ranges, refer to the VLAN-aware bridge chapter.
Bonds with Vagrant in Cumulus VX
Bonds (or LACP Etherchannels) fail to work in a Vagrant setup unless the link is set to promiscuous mode. This is a limitation on virtual topologies only, and is not needed on real hardware.
For more information on using Cumulus VX and Vagrant, refer to the Cumulus VX documentation.
With LNV, Unique Node ID Required for vxrd in Cumulus VX
vxrd requires a unique
node_id for each individual switch. This
node_id is based off the first interface's MAC address; when using certain virtual topologies like Vagrant, both leaf switches within an MLAG pair can generate the same exact unique
node_id. You must configure one of the
node_ids manually (or make sure the first interface always has a unique MAC address), as they are not unique.
To verify the
node_id that gets configured by your switch, use the
vxrdctl get config command:
To set the
/etc/vxrd.confin a text editor.
node_idvalue within the
commonsection, then save the file:
Ensure that each leaf has a separate
node_id so that active-active mode can function correctly.
- Static VXLAN Configurations
- Ethernet Virtual Private Network - EVPN
- Lightweight Network Virtualization Overview
- VXLAN Active-Active Mode
- VXLAN Routing
- VXLAN Scale
- Hybrid Cloud Connectivity with QinQ and VXLANs
- Troubleshooting VXLANs
- Virtualization Integrations