If you have existing vendor equipments that support OpenFlow, it would be a great way to start your migration path. Vendors such as Cisco, Juniper, and Arista, all have equipments that support OpenFlow. The depth of support and the degree of difficulty varies from vendor to vendor and in some cases, from device to device. Given some of the limitation as we will see later on, using incumbent vendor switch would be a great way to migrate to OpenFlow if you already have matched gears in your possession. In this section, I will use Arista gears running EOS 4.17 as an example. For more details, you can consult the EOS 4.17 OpenFlow configuration manual at https://www.arista.com/assets/data/docs/Manuals/EOS-4.17.0F-Manual.pdf.

In EOS 4.17, Arista supports OpenFlow in 7050 and 7050X series of switches. However, there are a number of limitations stated in the manual, so read through them to save yourself from some troubleshooting headache in future. For example, it is stated that for switch to controller interaction, TLS is not supported. If you had not read that before you tried to implement TLS, you could have spent hours troubleshooting fruitlessly. Arista also recommends using OpenFlow for the switch, even though in configuration you can bind to certain VLANs.

switch(config)#openflow
switch(config-openflow)#controller tcp:1.2.3.4:6633
switch(config-openflow)#bind mode vlan
switch(config-openflow)#bind vlan 1
switch(config-OpenFlow)#no shutdown

You can examine the state of OpenFlow:

switch(config)# show openflow
OpenFlow configuration: Enabled
DPID: 0x0000001c73111a92
Description: sw3-Arista
Controllers:
 configured: tcp:172.22.28.228:6633
 connected: tcp:172.22.28.228:6633
 connection count: 3
 keepalive period: 10 sec
Flow table state: Enabled
Flow table profile: full-match
Bind mode: VLAN
 VLANs: 1-2
 native VLAN: 1
IP routing state: Disabled
Shell command execution: Disabled
Total matched: 7977645 packets

Arista also supports an OpenFlow-like feature called DirectFlow. It supports all OpenFlow 1.0 match criteria and actions. The big difference between DirectFlow and OpenFlow is that there is no default match action, so table-miss entries are to follow the normal L2/L3 pipeline. DirectFlow is mutually exclusive with OpenFlow. Configuration is straight forward:

switch(config)#directflow
switch(config-directflow)#
switch(config-directflow)#no shutdown
switch(config-directflow)#flow Test1
switch(config-directflow-Test1)#match ethertype ip
switch(config-directflow-Test1)#match source ip 10.10.10.10
switch(config-directflow-Test1)#action egress mirror ethernet 7
switch(config-directflow-Test1)#action set destination mac 0000.aaaa.bbbb

The Arista example demonstrates the limitation we have discussed. The supportability of OpenFlow from incumbent vendor varies from device to software. The vendors typically add their own flavor as they see fit. We have seen an example of Arista, but they are not alone in that each vendor have their own limitation from years of building non-OpenFlow devices. However, if you already have some vendor equipment that matches the criteria, which is a big if, it is a great way to get started.