Summary:
Name Bytes Mask RW? Prereqs NXM/OXM Support
──────── ────── ───── ──── ──────── ─────────────────────
arp_op 2 no yes ARP OF 1.2+ and OVS 1.1+
arp_spa 4 yes yes ARP OF 1.2+ and OVS 1.1+
arp_tpa 4 yes yes ARP OF 1.2+ and OVS 1.1+
arp_sha 6 yes yes ARP OF 1.2+ and OVS 1.1+
arp_tha 6 yes yes ARP OF 1.2+ and OVS 1.1+
In theory, Address Resolution Protocol, or ARP, is a generic
protocol generic protocol that can be used to obtain the hardware
address that corresponds to any higher-level protocol address. In
contemporary usage, ARP is used only in Ethernet networks to
obtain the Ethernet address for a given IPv4 address. OpenFlow
and Open vSwitch only support this usage of ARP. For this use
case, an ARP packet has the following format, with the ARP fields
exposed as Open vSwitch fields highlighted:
Ethernet ARP
<-----------> <---------------------------------->
48 48 16 16 16 8 8 16 48 16 48 16
+---+---+-----+ +---+-----+---+---+--+---+---+---+---+
|dst|src|type | |hrd| pro |hln|pln|op|sha|spa|tha|tpa|
+---+---+-----+ +---+-----+---+---+--+---+---+---+---+
0x806 1 0x800 6 4
The ARP fields are also used for RARP, the Reverse Address
Resolution Protocol, which shares ARP's wire format.
ARP Opcode Field
Name: arp_op
Width: 16 bits
Format: decimal
Masking: not maskable
Prerequisites: ARP
Access: read/write
OpenFlow 1.0: yes (exact match only)
OpenFlow 1.1: yes (exact match only)
OXM: OXM_OF_ARP_OP (21) since OpenFlow 1.2 and Open
vSwitch 1.7
NXM: NXM_OF_ARP_OP (15) since Open vSwitch 1.1
Even though this is a 16-bit field, Open vSwitch does not support
ARP opcodes greater than 255; it treats them to zero. This works
adequately because in practice ARP and RARP only use opcodes 1
through 4.
ARP Source IPv4 Address Field
Name: arp_spa
Width: 32 bits
Format: IPv4
Masking: arbitrary bitwise masks
Prerequisites: ARP
Access: read/write
OpenFlow 1.0: yes (CIDR match only)
OpenFlow 1.1: yes
OXM: OXM_OF_ARP_SPA (22) since OpenFlow 1.2 and Open
vSwitch 1.7
NXM: NXM_OF_ARP_SPA (16) since Open vSwitch 1.1
ARP Target IPv4 Address Field
Name: arp_tpa
Width: 32 bits
Format: IPv4
Masking: arbitrary bitwise masks
Prerequisites: ARP
Access: read/write
OpenFlow 1.0: yes (CIDR match only)
OpenFlow 1.1: yes
OXM: OXM_OF_ARP_TPA (23) since OpenFlow 1.2 and Open
vSwitch 1.7
NXM: NXM_OF_ARP_TPA (17) since Open vSwitch 1.1
ARP Source Ethernet Address Field
Name: arp_sha
Width: 48 bits
Format: Ethernet
Masking: arbitrary bitwise masks
Prerequisites: ARP
Access: read/write
OpenFlow 1.0: not supported
OpenFlow 1.1: not supported
OXM: OXM_OF_ARP_SHA (24) since OpenFlow 1.2 and Open
vSwitch 1.7
NXM: NXM_NX_ARP_SHA (17) since Open vSwitch 1.1
ARP Target Ethernet Address Field
Name: arp_tha
Width: 48 bits
Format: Ethernet
Masking: arbitrary bitwise masks
Prerequisites: ARP
Access: read/write
OpenFlow 1.0: not supported
OpenFlow 1.1: not supported
OXM: OXM_OF_ARP_THA (25) since OpenFlow 1.2 and Open
vSwitch 1.7
NXM: NXM_NX_ARP_THA (18) since Open vSwitch 1.1
