LNV VXLAN Active-Active Mode
LNV 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.
Terminology and Definitions
Term | Definition |
|---|---|
vxrd | The VXLAN registration daemon. The daemon runs on the switch that is mapping VLANs to VXLANs. You must configure the |
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. |
vxsnd | The VXLAN service node daemon that you can run to register multiple VTEPs. |
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 | 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 LNV, anycast is used in two places:
|
ASIC | Application-specific integrated circuit; also referred to as hardware or hardware accelerated. Encapsulation and decapsulation are required for the best performance VXLAN-supported ASIC. |
RIOT | 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. |
Configuring LNV Active-active Mode
LNV requires the following underlying technologies to work correctly.
Technology | More Information |
|---|---|
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 demonstration are provided below. |
LNV | Refer to the LNV chapter for more detailed configuration information. Configurations for the 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. |
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. 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.
Failure Scenario Behaviors
| Scenario | Behavior |
|---|---|
| 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. |
clagd is stopped. | 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. | clagd brings up all the VXLAN interfaces after the reload timer expires with the configured anycast IP address. This allows the VXLAN interface to be up and running on both switches even though peering is not established. |
| 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. |
Checking VXLAN Interface Configuration Consistency
The LNV 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.
Configuring 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.
leaf01: /etc/network/interfaces snippet
auto lo
iface lo inet loopback
address 10.0.0.11/32
vxrd-src-ip 10.0.0.11
vxrd-svcnode-ip 10.10.10.10
clagd-vxlan-anycast-ip 10.10.10.20
leaf02: /etc/network/interfaces snippet
auto lo
iface lo inet loopback
address 10.0.0.12/32
vxrd-src-ip 10.0.0.12
vxrd-svcnode-ip 10.10.10.10
clagd-vxlan-anycast-ip 10.10.10.20
Explanation of Variables
Variable | Explanation |
|---|---|
| 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. |
| The anycast address for the MLAG pair to share and bind to when MLAG is up and running. |
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.
FRRouting Configuration
You can configure the layer 3 fabric using BGP or OSPF. The following example uses BGP unnumbered. The MLAG switch configuration for the topology above is shown below.
Layer 3 IP Addressing
The IP address configuration for this example:
spine01: | spine02: |
leaf01: | leaf02: |
leaf3: | leaf4: |
Host Configuration
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.
server01 | server03 |
Enable the Registration Daemon
You must enable the registration daemon (vxrd) on each ToR switch
acting as a VTEP that is participating in LNV. The daemon is installed
by default.
Open the
/etc/default/vxrdconfiguration file in a text editor.Enable the daemon, then save the file.
START=yesRestart the
vxrddaemon.cumulus@leaf:~$ sudo systemctl restart vxrd.service
Configuring a VTEP
The registration node is configured earlier in
/etc/network/interfaces; no additional configuration is typically
needed. Alternatively, you can perform the configuration in the
/etc/vxrd.conf file, 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:
START=yesRestart the daemon.
cumulus@spine:~$ sudo systemctl restart vxsnd.service
Configuring the Service Node
To configure the service node daemon, edit the /etc/vxsnd.conf
configuration file:
spine01: /etc/vxsnd.conf Full configuration of vxsnd.conf | spine02: /etc/vxsnd.conf Full configuration of vxsnd.conf |
Considerations for Virtual Topologies Using Cumulus VX
Node ID
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:
cumulus@leaf01$ vxrdctl get config
{
"concurrency": 1000,
"config_check_rate": 60,
"debug": false,
"eventlet_backdoor_port": 9000,
"head_rep": true,
"holdtime": 90,
"logbackupcount": 14,
"logdest": "syslog",
"logfilesize": 512000,
"loglevel": "INFO",
"max_packet_size": 1500,
"node_id": 13,
"pidfile": "/var/run/vxrd.pid",
"refresh_rate": 3,
"src_ip": "10.2.1.50",
"svcnode_ip": "10.10.10.10",
"udsfile": "/var/run/vxrd.sock",
"vxfld_port": 10001
}
To set the node_id manually:
Open
/etc/vxrd.confin a text editor.Set the
node_idvalue within thecommonsection, then save the file:[common] node_id = 13
Ensure that each leaf has a separate node_id so that LNV can function
correctly.
Bonds with Vagrant
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.
auto swp49
iface swp49
#for vagrant so bonds work correctly
post-up ip link set $IFACE promisc on
auto swp50
iface swp50
#for vagrant so bonds work correctly
post-up ip link set $IFACE promisc on
For more information on using Cumulus VX and Vagrant, refer to the Cumulus VX documentation.
Troubleshooting with LNV Active-active
In addition to
troubleshooting for single-attached LNV,
there is now the MLAG daemon (clagd) to consider. The clagctl command
gives the output of MLAG behavior and any inconsistencies that might
arise between a MLAG pair.
cumulus@leaf01$ clagctl
The peer is alive
Our Priority, ID, and Role: 32768 44:38:39:00:00:35 primary
Peer Priority, ID, and Role: 32768 44:38:39:00:00:36 secondary
Peer Interface and IP: peerlink.4094 169.254.1.2
VxLAN Anycast IP: 10.10.10.30
Backup IP: 10.0.0.14 (inactive)
System MAC: 44:38:39:ff:40:95
CLAG Interfaces
Our Interface Peer Interface CLAG Id Conflicts Proto-Down Reason
---------------- ---------------- ------- -------------------- -----------------
bond0 bond0 1 - -
vxlan20 vxlan20 - - -
vxlan1 vxlan1 - - -
vxlan10 vxlan10 - - -
The additions to normal MLAG behavior are the following:
Output | Explanation |
|---|---|
VXLAN Anycast IP: 10.10.10.30 | 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
cumulus@leaf02$ clagctl
The peer is alive
Peer Priority, ID, and Role: 32768 44:38:39:00:00:11 primary
Our Priority, ID, and Role: 32768 44:38:39:00:00:12 secondary
Peer Interface and IP: peerlink.4094 169.254.1.1
VxLAN Anycast IP: 10.10.10.20
Backup IP: 10.0.0.11 (inactive)
System MAC: 44:38:39:ff:40:94
CLAG Interfaces
Our Interface Peer Interface CLAG Id Conflicts Proto-Down Reason
---------------- ---------------- ------- -------------------- -----------------
bond0 bond0 1 - -
vxlan20 vxlan20 - - -
vxlan1 vxlan1 - - -
vxlan10 - - - vxlan-single
Caveats and Errata
- 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.
- Active-active mode only works with LNV in this release. Integration with controller-based VXLANs, such as VMware NSX and Midokura MidoNet will be supported in the future.