Deployment Guide

Exceptions

This section describes the constraints of OpenFlow.

• Dell Networking switches can operate as Hybrid switches (switches running OpenFlow and legacy functions simultaneously). You

cannot enable Legacy functionality (switching and routing) on OF ports or OF virtual local area networks (VLANs), as these interfaces

are controlled by an OpenFlow controller and are not available.

• Stacking of OpenFlow switches is not supported for the S4810, S4820T, S6000, or MXL switches. If you configure stacking but

disabled it in preparation for future stacking, the stack unit number must be zero to enable OpenFlow on S4810, S4820T, S6000, or

MXL switches.

• For OF ports and OF VLANs, the VLAN IDs used for OpenFlow must be unique; the VLAN IDs can be used for legacy functionality on

the same switch.

• Dell Networking does not recommend using global spanning tree protocol (STP) instances on ports with both legacy VLANs and OF

VLANs.

• Transport layer security (TLS) connections are not supported.

• Because controllers typically run their own version of link layer discovery protocol (LLDP), disable legacy LLDP on OF ports.

• To avoid session timeout issues if you change the system clock, you must disable and re-enable all existing OF instances.

• Emergency flows are not supported.

• Packet buffering is not supported.

• Data center bridging (DCB) and Internet small computer system interface (iSCSI) are not supported on OpenFlow interfaces.

• The following packet types can only be copied to the controller and cannot be forwarded from a physical switch port:

• STP BDPU

• LLDP

• GVRP

• ARP Replies

• 802.1x frames

• untagged broadcast packets received on an OF port

ACL Flow Exceptions

• Flooding (action “output=all” or “output=flood”) is supported on S4810, S4820T, S6000, and MXL switches.

• By default, ACL flows override flows installed in the L2 or L3 tables.

• Address resolution protocol (ARP) opcode, sender IP, and target IP matching are not supported.

L3 Flow Exceptions

• Non-zero integers for the idle timeout are not supported and are ignored for L3 flows. L3 flows are not aged out.

• For L3 flows, flow priority is not applicable. Instead, the destination IP (dst-ip) network mask length is used to prioritize the flow, with

longer mask lengths having priority over shorter mask lengths. For example, an L3 flow with a dst-ip network mask length of 32 has

priority over a flow with a dst-ip network mask length of 31.

• Time-to-live (TTL) is decremented for traffic forwarded using L3 flows.

L2 Flow Exceptions

• If you specify a non-zero idle timeout value for an L2 flow and there is no activity or traffic, the flow is aged out according to the MAC

address table aging time configured on the switch. If the idle timeout value is zero, the flow is not aged.

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