Internet Assigned Numbers Authority

Address Resolution Protocol (ARP) Parameters

Last Updated
Reverse Address Resolution Protocol Operation Codes
The Reverse Address Resolution Protocol (RARP) specified in [RFC903]
uses the "Reverse" codes below.

The Dynamic Reverse Address Resolution Protocol (DRARP) uses the
"DRARP" codes below.  For further information, see [RFC1931].

The Inverse Address Resolution Protocol (IARP) specified in [RFC2390]
uses the "InARP" codes below.
Available Formats



Plain text

Registries included below

Operation Codes

Registration Procedure(s)
IETF Review or IESG Approval
Available Formats

Number Operation Code (op) References
0 Reserved [RFC5494]
1 REQUEST [RFC826][RFC5227]
2 REPLY [RFC826][RFC5227]
3 request Reverse [RFC903]
4 reply Reverse [RFC903]
5 DRARP-Request [RFC1931]
6 DRARP-Reply [RFC1931]
7 DRARP-Error [RFC1931]
8 InARP-Request [RFC2390]
9 InARP-Reply [RFC2390]
10 ARP-NAK [RFC1577]
11 MARS-Request [Grenville_Armitage]
12 MARS-Multi [Grenville_Armitage]
13 MARS-MServ [Grenville_Armitage]
14 MARS-Join [Grenville_Armitage]
15 MARS-Leave [Grenville_Armitage]
16 MARS-NAK [Grenville_Armitage]
17 MARS-Unserv [Grenville_Armitage]
18 MARS-SJoin [Grenville_Armitage]
19 MARS-SLeave [Grenville_Armitage]
20 MARS-Grouplist-Request [Grenville_Armitage]
21 MARS-Grouplist-Reply [Grenville_Armitage]
22 MARS-Redirect-Map [Grenville_Armitage]
23 MAPOS-UNARP [Mitsuru_Maruyama][RFC2176]
24 OP_EXP1 [RFC5494]
25 OP_EXP2 [RFC5494]
26-65534 Unassigned
65535 Reserved [RFC5494]

Hardware Types

Carlos Pignataro
Available Formats

Range Registration Procedures Note
requests for values below 256 Expert Review
requests for more than one value Expert Review
requests for one value greater than 255 First Come First Served
requests for one value, no value specified First Come First Served can only be assigned a two-octet value (i.e., a value greater than 255)
Number Hardware Type (hrd) Reference
0 Reserved [RFC5494]
1 Ethernet (10Mb) [Jon_Postel]
2 Experimental Ethernet (3Mb) [Jon_Postel]
3 Amateur Radio AX.25 [Philip_Koch]
4 Proteon ProNET Token Ring [Avri_Doria]
5 Chaos [Gill_Pratt]
6 IEEE 802 Networks [Jon_Postel]
7 ARCNET [RFC1201]
8 Hyperchannel [Jon_Postel]
9 Lanstar [Tom_Unger]
10 Autonet Short Address [Mike_Burrows]
11 LocalTalk [Joyce_K_Reynolds]
12 LocalNet (IBM PCNet or SYTEK LocalNET) [Joseph Murdock]
13 Ultra link [Rajiv_Dhingra]
14 SMDS [George_Clapp]
15 Frame Relay [Andy_Malis]
16 Asynchronous Transmission Mode (ATM) [[JXB2]]
17 HDLC [Jon_Postel]
18 Fibre Channel [RFC4338]
19 Asynchronous Transmission Mode (ATM) [RFC2225]
20 Serial Line [Jon_Postel]
21 Asynchronous Transmission Mode (ATM) [Mike_Burrows]
22 MIL-STD-188-220 [Herb_Jensen]
23 Metricom [Jonathan_Stone]
24 IEEE 1394.1995 [Myron_Hattig]
25 MAPOS [Mitsuru_Maruyama][RFC2176]
26 Twinaxial [Marion_Pitts]
27 EUI-64 [Kenji_Fujisawa]
28 HIPARP [Jean_Michel_Pittet]
29 IP and ARP over ISO 7816-3 [Scott_Guthery]
30 ARPSec [Jerome_Etienne]
31 IPsec tunnel [RFC3456]
32 InfiniBand (TM) [RFC4391]
33 TIA-102 Project 25 Common Air Interface (CAI) [Jeff Anderson, Telecommunications Industry of America (TIA) TR-8.5 Formulating Group, <cja015&>, June 2004]
34 Wiegand Interface [Scott_Guthery_2]
35 Pure IP [Inaky_Perez-Gonzalez]
36 HW_EXP1 [RFC5494]
37 HFI [Tseng-Hui_Lin]
38 Unified Bus (UB) [Wei_Pan]
39-255 Unassigned
256 HW_EXP2 [RFC5494]
257 AEthernet [Geoffroy_Gramaize]
258-65534 Unassigned
65535 Reserved [RFC5494]

Protocol Type

Registration Procedure(s)
The Ethertype space is administered as described in [RFC5342].
These numbers share the Ethertype space. See [].
No registrations at this time.

Contact Information

ID Name Contact URI Last Updated
[Andy_Malis] Andy Malis mailto:agmalis& 2013-05-28
[Avri_Doria] Avri Doria mailto:avri& 1994-12
[Geoffroy_Gramaize] Geoffroy Gramaize mailto:geoffroy.iana& 2016-07-20
[George_Clapp] George Clapp mailto:meritec!clapp&
[Gill_Pratt] Gill Pratt
[Grenville_Armitage] Grenville Armitage mailto:gja& 1995-04
[Herb_Jensen] Herb Jensen mailto:hwjensen& 1995-02
[Inaky_Perez-Gonzalez] Inaky Perez-Gonzalez mailto:inaky.perez-gonzalez& 2008-10-01
[Jean_Michel_Pittet] Jean-Michel Pittet mailto:jmp& 1998-11
[Jerome_Etienne] Jerome Etienne mailto:jetienne& 2000-06
[Jon_Postel] Jon Postel mailto:postel&
[Jonathan_Stone] Jonathan Stone mailto:jonathan& 1996-05
[Joyce_K_Reynolds] Joyce K. Reynolds mailto:jkrey&
[Kenji_Fujisawa] Kenji Fujisawa mailto:fujisawa& 1998-10
[Marion_Pitts] Marion Pitts mailto:marionp& 1997-05
[Mike_Burrows] Mike Burrows mailto:burrows&
[Mitsuru_Maruyama] Mitsuru Maruyama mailto:mitsuru& 1997-03
[Myron_Hattig] Myron Hattig mailto:Myron_Hattig& 1997-02
[Philip_Koch] Philip Koch mailto:Philip.Koch&
[Rajiv_Dhingra] Rajiv Dhingra mailto:rajiv&
[Scott_Guthery] Scott Guthery mailto:sguthery& 2000-03
[Scott_Guthery_2] Scott Guthery mailto:sguthery& 2008-09-25
[Tom_Unger] Tom Unger mailto:tom&citi.umich
[Tseng-Hui_Lin] Tseng-Hui Lin mailto:tsenglin&
[Wei_Pan] Wei Pan mailto:tarzan.pan& 2023-05-19