Administrator's Guide

6.4.1 Controller packet forwarding when hybrid mode is enabled
Figure 47 Controller operation with hybrid mode enabled
When hybrid mode is enabled (the default), the specific packet types for which the controller
monitors and overrides switch forwarding rules depends on the applications installed and running
in the controller. That is, the controller overrides normal packet forwarding rules in the OpenFlow
switch with application-specific forwarding rules, such as:
• copying ARP request/reply and DHCP offer/ACK packets to the controller so that it can
discover end-hosts
• stealing BDDP packets to the controller so that it can discover inter-switch links
• changing the priority on Lync packets to improve instant messaging speed
• monitoring DNS requests to detect dangerous end-host behavior
Packets in flows that the controller does not examine or direct are forwarded through normal
switching operations without controller intervention.
NOTE: HP recommends that hybrid mode be enabled when controlling traditional, established
networks where applications-related traffic is responsible for only a subset of the overall traffic load
on the network. Hybrid mode is commonly enabled in established networks where new applications
are installed and running on the controller, creating a need to override normal switching behavior
for specific flows.
6.4.2 Learning more about hybrid mode
For more on hybrid mode as it relates to OpenFlow, see the latest OpenFlow Switch Specification
on the Open Networking Foundation website. For a list of HPN switches that support OpenFlow
operation, see the latest edition of the HP VAN SDN Controller and Applications Support Matrix.
78 Hybrid mode for controlling packet-forwarding