LINK-LAYER HEADER TYPES

The table below lists link-layer header types used in pcap and pcap-ng capture files. The LINKTYPE_ name is the name given to that link-layer header type, and the LINKTYPE_ value is the numerical value used in capture files. The DLT_ name is the name corresponding to the value (specific to the packet capture method and device type) returned by pcap_datalink(3PCAP); in most cases, as pcap-linktype(7) mentions it, the LINKTYPE_ value and DLT_ value are the same, but, in some cases, they differ, for reasons of binary compatibility, with the DLT_ value being different on different platforms.

Note that these values correspond to particular header formats; there might be multiple link-layer header types for a given link-layer protocol, as, for a given link-layer header type, the header for the link-layer protocol might be preceded by a pseudo-header giving additional information, or might be transformed in some way from the way it's specified for that link-layer protocol, e.g. fields in the link-layer protocol header might be removed, added, moved, or modified.

Assigned and Reserved Values

  • Values in the range DLT_USER0–DLT_USER15 (147–162, both inclusive) are reserved for private use; if you have some link-layer header type that you want to use within your organization, with the capture files using that link-layer header type not ever be sent outside your organization, you can use one or more of these values. No libpcap release will use these for any purpose, nor will any tcpdump release use them, either.

    Do NOT use these in capture files that you expect anybody not using your private versions of capture-file-reading tools to read; in particular, do NOT use them in products, otherwise you may find that people won't be able to use tcpdump, or snort, or Wireshark, or… to read the capture files from your firewall/intrusion detection/traffic monitoring/etc. appliance, or whatever product uses that link-layer header type value, and you may also find that the developers of those applications will not accept patches to let them read those files.

    Also, do not use them if somebody might send you a capture using them for their private type and tools using them for your private type would have to read them.

  • All other values listed in the table below are assigned.

  • Any values not listed in the table below are reserved for future use and can be assigned subject to due process.

How To Assign a New Value

Please remember that initial prototyping and experimentation can and should be done using the DLT_USERx private use values. If you need a value for a particular set of link-layer headers, you must request one; to do so:

  • Subscribe to the mailing list and send a message with the request.

    Please include either an indication of the standard that describes the link-layer headers, a link to a permanent and public page describing the link-layer headers, or a detailed description of the link-layer headers. If the headers do not exactly match the description in a standard or standards—for example, if fields are added, removed, or reordered, or have their size, endianness or format changed—please describe all differences in detail.

  • Prepare libpcap changes for the new value:

    • In pcap/dlt.h add the new DLT_ value and the associated comments, increment DLT_MATCHING_MAX.
    • In pcap-common.c add the new LINKTYPE_ value (omit the comments if the previous step explains everything sufficiently well), increment LINKTYPE_MATCHING_MAX.
    • In pcap.c add the new value to dlt_choices[].
    • Check everything and open a pull request with the changes.

  • Prepare web site changes for the new value:

    • If there is no other specification readily available for the new header type, create a new htmlsrc/linktypes/LINKTYPE_xxxxx.html file and document the new header structure.
    • In htmlsrc/linktypes.html (this file) add the new value to the bottom of the table.
    • Generate complete HTML files from the file(s) above as explained here.
    • Check everything and open a pull request with the changes.

  • Have patience.

    Be ready to answer questions and to address any technical issues that emerge during the review. This sometimes takes longer than expected, but it is important to get every detail right because after the assignment the new header structure should be set in stone.

Warning

Do NOT add new values to this list except as explained above. Otherwise, you run the risk of using a value that's already being used for some other purpose, and of having tools that read libpcap-format captures not being able to handle captures with your new link-layer header type value, with no hope that they will ever be changed to do so (as that would destroy their ability to read captures using that value for that other purpose).

Do NOT use any of these link-layer header type values unless your link-layer headers EXACTLY match the specification. If they do not exactly match, request a new link-layer header type for them.

Link-layer header type values

LINKTYPE_ name LINKTYPE_ value Corresponding DLT_ name Description
LINKTYPE_NULL 0 DLT_NULL BSD loopback encapsulation; the link layer header is a 4-byte field, in host byte order, containing a value of 2 for IPv4 packets, a value of either 24, 28, or 30 for IPv6 packets, a value of 7 for OSI packets, or a value of 23 for IPX packets. All of the IPv6 values correspond to IPv6 packets; code reading files should check for all of them.

Note that ``host byte order'' is the byte order of the machine on that the packets are captured; if a live capture is being done, ``host byte order'' is the byte order of the machine capturing the packets, but if a ``savefile'' is being read, the byte order is not necessarily that of the machine reading the capture file.

LINKTYPE_ETHERNET 1 DLT_EN10MB IEEE 802.3 Ethernet (10Mb, 100Mb, 1000Mb, and up); the 10MB in the DLT_ name is historical.
LINKTYPE_EXP_ETHERNET 2 DLT_EN3MB Experimental Ethernet (3Mb).
LINKTYPE_AX25 3 DLT_AX25 AX.25 packet, with nothing preceding it.
LINKTYPE_PRONET 4 DLT_PRONET Proteon ProNET Token Ring.
LINKTYPE_CHAOS 5 DLT_CHAOS Chaos.
LINKTYPE_IEEE802_5 6 DLT_IEEE802 IEEE 802.5 Token Ring; the IEEE802, without _5, in the DLT_ name is historical.
LINKTYPE_ARCNET_BSD 7 DLT_ARCNET ARCNET Data Packets, as described by the ARCNET Trade Association standard ATA 878.1-1999, but without the Starting Delimiter, Information Length, or Frame Check Sequence fields, and with only the first ISU of the Destination Identifier. For most packet types, ARCNET Trade Association draft standard ATA 878.2 is also used. See also RFC 1051 and RFC 1201; for RFC 1051 frames, ATA 878.2 is not used.
LINKTYPE_SLIP 8 DLT_SLIP SLIP, encapsulated with a LINKTYPE_SLIP header.
LINKTYPE_PPP 9 DLT_PPP PPP, as per RFC 1661 and RFC 1662; if the first 2 bytes are 0xff and 0x03, it's PPP in HDLC-like framing, with the PPP header following those two bytes, otherwise it's PPP without framing, and the packet begins with the PPP header. The data in the frame is not octet-stuffed or bit-stuffed.
LINKTYPE_FDDI 10 DLT_FDDI FDDI, as specified by ANSI INCITS 239-1994.
32 DLT_REDBACK_SMARTEDGE Redback SmartEdge 400/800.
LINKTYPE_PPP_HDLC 50 DLT_PPP_SERIAL PPP in HDLC-like framing, as per RFC 1662, or Cisco PPP with HDLC framing, as per section 4.3.1 of RFC 1547; the first byte will be 0xFF for PPP in HDLC-like framing, and will be 0x0F or 0x8F for Cisco PPP with HDLC framing. The data in the frame is not octet-stuffed or bit-stuffed.
LINKTYPE_PPP_ETHER 51 DLT_PPP_ETHER PPPoE; the packet begins with a PPPoE header, as per RFC 2516.
LINKTYPE_SYMANTEC_FIREWALL 99 DLT_SYMANTEC_FIREWALL Symantec Enterprise (ex-Axent Raptor) firewall.
LINKTYPE_ATM_RFC1483 100 DLT_ATM_RFC1483 RFC 1483 LLC/SNAP-encapsulated ATM; the packet begins with an ISO 8802-2 (formerly known as IEEE 802.2) LLC header.
LINKTYPE_RAW 101 DLT_RAW Raw IP; the packet begins with an IPv4 or IPv6 header, with the version field of the header indicating whether it's an IPv4 or IPv6 header.
LINKTYPE_C_HDLC 104 DLT_C_HDLC Cisco PPP with HDLC framing, as per section 4.3.1 of RFC 1547.
LINKTYPE_IEEE802_11 105 DLT_IEEE802_11 IEEE 802.11 wireless LAN.
LINKTYPE_ATM_CLIP 106 DLT_ATM_CLIP Linux Classical IP over ATM.
LINKTYPE_FRELAY 107 DLT_FRELAY Frame Relay LAPF frames, beginning with a ITU-T Recommendation Q.922 LAPF header starting with the address field, and without an FCS at the end of the frame.
LINKTYPE_LOOP 108 DLT_LOOP OpenBSD loopback encapsulation; the link-layer header is a 4-byte field, in network byte order, containing a value of 2 for IPv4 packets, a value of either 24, 28, or 30 for IPv6 packets, a value of 7 for OSI packets, or a value of 23 for IPX packets. All of the IPv6 values correspond to IPv6 packets; code reading files should check for all of them.
LINKTYPE_ENC 109 DLT_ENC Encapsulated packets for IPsec.
LINKTYPE_NETBSD_HDLC 112 DLT_HDLC Cisco HDLC.
LINKTYPE_LINUX_SLL 113 DLT_LINUX_SLL Linux "cooked" capture encapsulation.
LINKTYPE_LTALK 114 DLT_LTALK Apple LocalTalk; the packet begins with an AppleTalk LocalTalk Link Access Protocol header, as described in chapter 1 of Inside AppleTalk, Second Edition.
115 DLT_ECONET Acorn Econet.
116 DLT_IPFILTER OpenBSD ipfilter.
LINKTYPE_PFLOG 117 DLT_PFLOG OpenBSD pflog; the link-layer header contains a struct pfloghdr structure, as defined by the host on that the file was saved. (This differs from operating system to operating system and release to release; there is nothing in the file to indicate what the layout of that structure is.)
118 DLT_CISCO_IOS Cisco internal use.
LINKTYPE_IEEE802_11_PRISM 119 DLT_PRISM_HEADER Prism monitor mode information followed by an 802.11 header.
120 DLT_AIRONET_HEADER Reserved for Aironet 802.11 cards, with an Aironet link-layer header.
LINKTYPE_IP_OVER_FC 122 DLT_IP_OVER_FC RFC 2625 IP-over-Fibre Channel, with the link-layer header being the Network_Header as described in that RFC.
LINKTYPE_SUNATM 123 DLT_SUNATM ATM traffic, encapsulated as per the scheme used by SunATM devices.
124 DLT_RIO RapidIO.
125 DLT_PCI_EXP PCI Express.
126 DLT_AURORA Xilinx Aurora.
LINKTYPE_IEEE802_11_RADIOTAP 127 DLT_IEEE802_11_RADIO Radiotap link-layer information followed by an 802.11 header.
LINKTYPE_TZSP 128 DLT_TZSP Tazmen Sniffer Protocol (TZSP) is a generic encapsulation for any other link type, which includes a means to include meta-information with the packet, e.g. signal strength and channel for 802.11 packets.
LINKTYPE_ARCNET_LINUX 129 DLT_ARCNET_LINUX ARCNET Data Packets, as described by the ARCNET Trade Association standard ATA 878.1-1999, but without the Starting Delimiter, Information Length, or Frame Check Sequence fields, with only the first ISU of the Destination Identifier, and with an extra two-ISU offset field following the Destination Identifier. For most packet types, ARCNET Trade Association draft standard ATA 878.2 is also used; however, no exception frames are supplied, and reassembled frames, rather than fragments, are supplied. See also RFC 1051 and RFC 1201; for RFC 1051 frames, ATA 878.2 is not used.
LINKTYPE_JUNIPER_MLPPP 130 DLT_JUNIPER_MLPPP Juniper Networks private data link type.
LINKTYPE_JUNIPER_MLFR 131 DLT_JUNIPER_MLFR Juniper Networks private data link type.
LINKTYPE_JUNIPER_ES 132 DLT_JUNIPER_ES Juniper Networks private data link type.
LINKTYPE_JUNIPER_GGSN 133 DLT_JUNIPER_GGSN Juniper Networks private data link type.
LINKTYPE_JUNIPER_MFR 134 DLT_JUNIPER_MFR Juniper Networks private data link type.
LINKTYPE_JUNIPER_ATM2 135 DLT_JUNIPER_ATM2 Juniper Networks private data link type.
LINKTYPE_JUNIPER_SERVICES 136 DLT_JUNIPER_SERVICES Juniper Networks private data link type.
LINKTYPE_JUNIPER_ATM1 137 DLT_JUNIPER_ATM1 Juniper Networks private data link type.
LINKTYPE_APPLE_IP_OVER_IEEE1394 138 DLT_APPLE_IP_OVER_IEEE1394 Apple IP-over-IEEE 1394 cooked header.
LINKTYPE_MTP2_WITH_PHDR 139 DLT_MTP2_WITH_PHDR Signaling System 7 Message Transfer Part Level 2, as specified by ITU-T Recommendation Q.703, preceded by a pseudo-header.
LINKTYPE_MTP2 140 DLT_MTP2 Signaling System 7 Message Transfer Part Level 2, as specified by ITU-T Recommendation Q.703.
LINKTYPE_MTP3 141 DLT_MTP3 Signaling System 7 Message Transfer Part Level 3, as specified by ITU-T Recommendation Q.704, with no MTP2 header preceding the MTP3 packet.
LINKTYPE_SCCP 142 DLT_SCCP Signaling System 7 Signalling Connection Control Part, as specified by ITU-T Recommendation Q.711, ITU-T Recommendation Q.712, ITU-T Recommendation Q.713, and ITU-T Recommendation Q.714, with no MTP3 or MTP2 headers preceding the SCCP packet.
LINKTYPE_DOCSIS 143 DLT_DOCSIS DOCSIS MAC frames, as described by the DOCSIS 3.1 MAC and Upper Layer Protocols Interface Specification or earlier specifications for MAC frames.
LINKTYPE_LINUX_IRDA 144 DLT_LINUX_IRDA Linux-IrDA packets, with a LINKTYPE_LINUX_IRDA header, with the payload for IrDA frames beginning with by the IrLAP header as defined by IrDA Data Specifications, including the IrDA Link Access Protocol specification.
LINKTYPE_IBM_SP 145 DLT_IBM_SP IBM SP switch.
LINKTYPE_IBM_SN 146 DLT_IBM_SN IBM Next Federation switch.
LINKTYPE_USER0–LINKTYPE_USER15 147–162 DLT_USER0–DLT_USER15 Reserved for private use; see above.
LINKTYPE_IEEE802_11_AVS 163 DLT_IEEE802_11_RADIO_AVS AVS monitor mode information followed by an 802.11 header.
LINKTYPE_JUNIPER_MONITOR 164 DLT_JUNIPER_MONITOR Juniper Networks private data link type.
LINKTYPE_BACNET_MS_TP 165 DLT_BACNET_MS_TP BACnet MS/TP frames, as specified by section 9.3 MS/TP Frame Format of ANSI/ASHRAE Standard 135, BACnet® - A Data Communication Protocol for Building Automation and Control Networks, including the preamble and, if present, the Data CRC.
LINKTYPE_PPP_PPPD 166 DLT_PPP_PPPD PPP in HDLC-like encapsulation, like LINKTYPE_PPP_HDLC, but with the 0xff address byte replaced by a direction indication—0x00 for incoming and 0x01 for outgoing.
LINKTYPE_JUNIPER_PPPOE 167 DLT_JUNIPER_PPPOE Juniper Networks private data link type.
LINKTYPE_JUNIPER_PPPOE_ATM 168 DLT_JUNIPER_PPPOE_ATM Juniper Networks private data link type.
LINKTYPE_GPRS_LLC 169 DLT_GPRS_LLC General Packet Radio Service Logical Link Control, as defined by 3GPP TS 04.64.
LINKTYPE_GPF_T 170 DLT_GPF_T Transparent-mapped generic framing procedure, as specified by ITU-T Recommendation G.7041/Y.1303.
LINKTYPE_GPF_F 171 DLT_GPF_F Frame-mapped generic framing procedure, as specified by ITU-T Recommendation G.7041/Y.1303.
LINKTYPE_GCOM_T1E1 172 DLT_GCOM_T1E1 Gcom's T1/E1 line monitoring equipment.
LINKTYPE_GCOM_SERIAL 173 DLT_GCOM_SERIAL Gcom's T1/E1 line monitoring equipment.
LINKTYPE_JUNIPER_PIC_PEER 174 DLT_JUNIPER_PIC_PEER Juniper Networks private data link type.
LINKTYPE_ERF_ETH 175 DLT_ERF_ETH An ERF header followed by Ethernet.
LINKTYPE_ERF_POS 176 DLT_ERF_POS An ERF header followed by Packet-over-SONET.
LINKTYPE_LINUX_LAPD 177 DLT_LINUX_LAPD Link Access Procedures on the D Channel (LAPD) frames, as specified by ITU-T Recommendation Q.920 and ITU-T Recommendation Q.921, captured via vISDN, with a LINKTYPE_LINUX_LAPD header, followed by the Q.921 frame, starting with the address field.
LINKTYPE_JUNIPER_ETHER 178 DLT_JUNIPER_ETHER Juniper Networks private data link type. Ethernet frames prepended with meta-information.
LINKTYPE_JUNIPER_PPP 179 DLT_JUNIPER_PPP Juniper Networks private data link type. PPP frames prepended with meta-information.
LINKTYPE_JUNIPER_FRELAY 180 DLT_JUNIPER_FRELAY Juniper Networks private data link type. Frame Relay frames prepended with meta-information.
LINKTYPE_JUNIPER_CHDLC 181 DLT_JUNIPER_CHDLC Juniper Networks private data link type. C-HDLC frames prepended with meta-information.
LINKTYPE_MFR 182 DLT_MFR FRF.16.1 Multi-Link Frame Relay frames, beginning with an FRF.12 Interface fragmentation format fragmentation header.
LINKTYPE_JUNIPER_VP 183 DLT_JUNIPER_VP Juniper Networks private data link type.
LINKTYPE_A429 184 DLT_A429 ARINC 429 frames. Every frame contains a 32-bit A429 label.
LINKTYPE_A653_ICM 185 DLT_A653_ICM ARINC 653 interpartition communication messages. Please refer to the A653-1 standard for more information.
LINKTYPE_USB_FREEBSD 186 DLT_USB_FREEBSD USB with FreeBSD header.
LINKTYPE_BLUETOOTH_HCI_H4 187 DLT_BLUETOOTH_HCI_H4 Bluetooth HCI UART transport layer; the frame contains an HCI packet indicator byte, as specified by the UART Transport Layer portion of the most recent Bluetooth Core specification, followed by an HCI packet of the specified packet type, as specified by the Host Controller Interface Functional Specification portion of the most recent Bluetooth Core Specification.
LINKTYPE_IEEE802_16_MAC_CPS 188 DLT_IEEE802_16_MAC_CPS IEEE 802.16 MAC Common Part Sublayer.
LINKTYPE_USB_LINUX 189 DLT_USB_LINUX USB packets, beginning with a Linux USB header, as specified by the struct usbmon_packet in the Documentation/usb/usbmon.txt file in the Linux source tree. Only the first 48 bytes of that header are present. All fields in the header are in host byte order. When performing a live capture, the host byte order is the byte order of the machine on that the packets are captured. When reading a pcap file, the byte order is the byte order for the file, as specified by the file's magic number; when reading a pcapng file, the byte order is the byte order for the section of the pcapng file, as specified by the Section Header Block.
LINKTYPE_CAN20B 190 DLT_CAN20B Controller Area Network (CAN) v. 2.0B.
LINKTYPE_IEEE802_15_4_LINUX 191 DLT_IEEE802_15_4_LINUX IEEE 802.15.4, with address fields padded, as is done by Linux drivers.
LINKTYPE_PPI 192 DLT_PPI Per-Packet Information information, as specified by the Per-Packet Information Header Specification, followed by a packet with the LINKTYPE_ value specified by the pph_dlt field of that header.
LINKTYPE_IEEE802_16_MAC_CPS_RADIO 193 DLT_IEEE802_16_MAC_CPS_RADIO IEEE 802.16 MAC Common Part Sublayer plus radiotap header.
LINKTYPE_JUNIPER_ISM 194 DLT_JUNIPER_ISM Juniper Networks private data link type.
LINKTYPE_IEEE802_15_4_WITHFCS 195 DLT_IEEE802_15_4_WITHFCS IEEE 802.15.4 Low-Rate Wireless Networks, with each packet having the FCS at the end of the frame.
LINKTYPE_SITA 196 DLT_SITA Various link-layer types, with a pseudo-header, for SITA.
LINKTYPE_ERF 197 DLT_ERF Various link-layer types, with a pseudo-header, for Endace DAG cards; encapsulates Endace ERF records.
LINKTYPE_RAIF1 198 DLT_RAIF1 Special header prepended to Ethernet packets when capturing from a u10 Networks board.
LINKTYPE_IPMB_KONTRON 199 DLT_IPMB_KONTRON IPMB packet for IPMI, beginning with a 2-byte header, followed by the I2C slave address, followed by the netFn and LUN, etc…
LINKTYPE_JUNIPER_ST 200 DLT_JUNIPER_ST Juniper Networks private data link type.
LINKTYPE_BLUETOOTH_HCI_H4_WITH_PHDR 201 DLT_BLUETOOTH_HCI_H4_WITH_PHDR Bluetooth HCI UART transport layer; the frame contains a 4-byte direction field, in network byte order (big-endian), the low-order bit of which is set if the frame was sent from the host to the controller and clear if the frame was received by the host from the controller, followed by an HCI packet indicator byte, as specified by the UART Transport Layer portion of the most recent Bluetooth Core specification, followed by an HCI packet of the specified packet type, as specified by the Host Controller Interface Functional Specification portion of the most recent Bluetooth Core Specification.
LINKTYPE_AX25_KISS 202 DLT_AX25_KISS AX.25 packet, with a 1-byte KISS header containing a type indicator.
LINKTYPE_LAPD 203 DLT_LAPD Link Access Procedures on the D Channel (LAPD) frames, as specified by ITU-T Recommendation Q.920 and ITU-T Recommendation Q.921, starting with the address field, with no pseudo-header.
LINKTYPE_PPP_WITH_DIR 204 DLT_PPP_WITH_DIR PPP, as per RFC 1661 and RFC 1662, preceded with a one-byte pseudo-header with a zero value meaning "received by this host" and a non-zero value meaning "sent by this host"; if the first 2 bytes are 0xff and 0x03, it's PPP in HDLC-like framing, with the PPP header following those two bytes, otherwise it's PPP without framing, and the packet begins with the PPP header. The data in the frame is not octet-stuffed or bit-stuffed.
LINKTYPE_C_HDLC_WITH_DIR 205 DLT_C_HDLC_WITH_DIR Cisco PPP with HDLC framing, as per section 4.3.1 of RFC 1547, preceded with a one-byte pseudo-header with a zero value meaning "received by this host" and a non-zero value meaning "sent by this host".
LINKTYPE_FRELAY_WITH_DIR 206 DLT_FRELAY_WITH_DIR Frame Relay LAPF frames, beginning with a one-byte pseudo-header with a zero value meaning "received by this host" (DCE->DTE) and a non-zero value meaning "sent by this host" (DTE->DCE), followed by an ITU-T Recommendation Q.922 LAPF header starting with the address field, and without an FCS at the end of the frame.
LINKTYPE_LAPB_WITH_DIR 207 DLT_LAPB_WITH_DIR Link Access Procedure, Balanced (LAPB), as specified by ITU-T Recommendation X.25, preceded with a one-byte pseudo-header with a zero value meaning "received by this host" (DCE->DTE) and a non-zero value meaning "sent by this host" (DTE->DCE).
LINKTYPE_IPMB_LINUX 209 DLT_IPMB_LINUX IPMB over an I2C circuit, with a Linux-specific pseudo-header.
LINKTYPE_FLEXRAY 210 DLT_FLEXRAY FlexRay automotive bus frames or symbols, preceded by a pseudo-header.
LINKTYPE_MOST 211 DLT_MOST Media Oriented Systems Transport (MOST) bus for multimedia transport.
LINKTYPE_LIN 212 DLT_LIN Local Interconnect Network (LIN) automotive bus, preceded by a pseudo-header.
LINKTYPE_X2E_SERIAL 213 DLT_X2E_SERIAL X2E-private data link type used for serial line capture.
LINKTYPE_X2E_XORAYA 214 DLT_X2E_XORAYA X2E-private data link type used for the Xoraya data logger family.
LINKTYPE_IEEE802_15_4_NONASK_PHY 215 DLT_IEEE802_15_4_NONASK_PHY IEEE 802.15.4 Low-Rate Wireless Networks, with each packet having the FCS at the end of the frame, and with the PHY-level data for the O-QPSK, BPSK, GFSK, MSK, and RCC DSS BPSK PHYs (4 octets of 0 as preamble, one octet of SFD, one octet of frame length + reserved bit) preceding the MAC-layer data (starting with the frame control field).
LINKTYPE_LINUX_EVDEV 216 DLT_LINUX_EVDEV Linux evdev events from /dev/input/eventN devices.
LINKTYPE_GSMTAP_UM 217 DLT_GSMTAP_UM GSM Um interface, preceded by a "gsmtap" header.
LINKTYPE_GSMTAP_ABIS 218 DLT_GSMTAP_ABIS GSM Abis interface, preceded by a "gsmtap" header.
LINKTYPE_MPLS 219 DLT_MPLS MPLS, with an MPLS label as the link-layer header.
LINKTYPE_USB_LINUX_MMAPPED 220 DLT_USB_LINUX_MMAPPED USB packets, beginning with a Linux USB header, as specified by the struct usbmon_packet in the Documentation/usb/usbmon.txt file in the Linux source tree. All 64 bytes of the header are present. All fields in the header are in host byte order. When performing a live capture, the host byte order is the byte order of the machine on that the packets are captured. When reading a pcap file, the byte order is the byte order for the file, as specified by the file's magic number; when reading a pcapng file, the byte order is the byte order for the section of the pcapng file, as specified by the Section Header Block. For isochronous transfers, the ndesc field specifies the number of isochronous descriptors that follow.
LINKTYPE_DECT 221 DLT_DECT DECT packets, with a pseudo-header.
LINKTYPE_AOS 222 DLT_AOS AOS Space Data Link Protocol.
LINKTYPE_WIHART 223 DLT_WIHART WirelessHART (Highway Addressable Remote Transducer) from the HART Communication Foundation (IEC/PAS 62591).
LINKTYPE_FC_2 224 DLT_FC_2 Fibre Channel FC-2 frames, beginning with a Frame_Header.
LINKTYPE_FC_2_WITH_FRAME_DELIMS 225 DLT_FC_2_WITH_FRAME_DELIMS Fibre Channel FC-2 frames, beginning an encoding of the SOF, followed by a Frame_Header, and ending with an encoding of the SOF.

The encodings represent the frame delimiters as 4-byte sequences representing the corresponding ordered sets, with K28.5 represented as 0xBC, and the D symbols as the corresponding byte values; for example, SOFi2, which is K28.5 - D21.5 - D1.2 - D21.2, is represented as 0xBC 0xB5 0x55 0x55.

LINKTYPE_IPNET 226 DLT_IPNET Solaris ipnet pseudo-header, followed by an IPv4 or IPv6 datagram.
LINKTYPE_CAN_SOCKETCAN 227 DLT_CAN_SOCKETCAN CAN (Controller Area Network) frames, with a pseudo-header followed by the frame payload.
LINKTYPE_IPV4 228 DLT_IPV4 Raw IPv4; the packet begins with an IPv4 header.
LINKTYPE_IPV6 229 DLT_IPV6 Raw IPv6; the packet begins with an IPv6 header.
LINKTYPE_IEEE802_15_4_NOFCS 230 DLT_IEEE802_15_4_NOFCS IEEE 802.15.4 Low-Rate Wireless Network, without the FCS at the end of the frame.
LINKTYPE_DBUS 231 DLT_DBUS Raw D-Bus messages, starting with the endianness flag, followed by the message type, etc., but without the authentication handshake before the message sequence.
LINKTYPE_JUNIPER_VS 232 DLT_JUNIPER_VS Juniper Networks private data link type.
LINKTYPE_JUNIPER_SRX_E2E 233 DLT_JUNIPER_SRX_E2E Juniper Networks private data link type.
LINKTYPE_JUNIPER_FIBRECHANNEL 234 DLT_JUNIPER_FIBRECHANNEL Juniper Networks private data link type.
LINKTYPE_DVB_CI 235 DLT_DVB_CI DVB-CI (DVB Common Interface for communication between a PC Card module and a DVB receiver), with the message format specified by the PCAP format for DVB-CI specification.
LINKTYPE_MUX27010 236 DLT_MUX27010 Variant of 3GPP TS 27.010 multiplexing protocol (similar to, but not the same as, 27.010).
LINKTYPE_STANAG_5066_D_PDU 237 DLT_STANAG_5066_D_PDU D_PDUs as described by NATO standard STANAG 5066, starting with the synchronization sequence, and including both header and data CRCs. The current version of STANAG 5066 is backwards-compatible with the 1.0.2 version, although newer versions are classified.
LINKTYPE_JUNIPER_ATM_CEMIC 238 DLT_JUNIPER_ATM_CEMIC Juniper Networks private data link type.
LINKTYPE_NFLOG 239 DLT_NFLOG Linux netlink NETLINK NFLOG socket log messages.
LINKTYPE_NETANALYZER 240 DLT_NETANALYZER Pseudo-header for Hilscher Gesellschaft für Systemautomation mbH netANALYZER devices, followed by an Ethernet frame, beginning with the MAC header and ending with the FCS.
LINKTYPE_NETANALYZER_TRANSPARENT 241 DLT_NETANALYZER_TRANSPARENT Pseudo-header for Hilscher Gesellschaft für Systemautomation mbH netANALYZER devices, followed by an Ethernet frame, beginning with the preamble, SFD, and MAC header, and ending with the FCS.
LINKTYPE_IPOIB 242 DLT_IPOIB IP-over-InfiniBand, as specified by RFC 4391 section 6.
LINKTYPE_MPEG_2_TS 243 DLT_MPEG_2_TS MPEG-2 Transport Stream transport packets, as specified by ISO 13818-1/ITU-T Recommendation H.222.0 (see table 2-2 of section 2.4.3.2 "Transport Stream packet layer").
LINKTYPE_NG40 244 DLT_NG40 Pseudo-header for ng4T GmbH's UMTS Iub/Iur-over-ATM and Iub/Iur-over-IP format as used by their ng40 protocol tester, followed by frames for the Frame Protocol as specified by 3GPP TS 25.427 for dedicated channels and 3GPP TS 25.435 for common/shared channels in the case of ATM AAL2 or UDP traffic, by SSCOP packets as specified by ITU-T Recommendation Q.2110 for ATM AAL5 traffic, and by NBAP packets for SCTP traffic.
LINKTYPE_NFC_LLCP 245 DLT_NFC_LLCP Pseudo-header for NFC LLCP packet captures, followed by frame data for the LLCP Protocol as specified by NFCForum-TS-LLCP_1.1.
LINKTYPE_PFSYNC 246 Packet filter state syncing.
LINKTYPE_INFINIBAND 247 DLT_INFINIBAND Raw InfiniBand frames, starting with the Local Routing Header, as specified in Chapter 5 "Data packet format" of InfiniBand™ Architectural Specification Release 1.2.1 Volume 1 - General Specifications.
LINKTYPE_SCTP 248 DLT_SCTP SCTP packets, as defined by RFC 4960, with no lower-level protocols such as IPv4 or IPv6.
LINKTYPE_USBPCAP 249 DLT_USBPCAP USB packets, beginning with a USBPcap header.
LINKTYPE_RTAC_SERIAL 250 DLT_RTAC_SERIAL Serial-line packet header for the Schweitzer Engineering Laboratories "RTAC" product, followed by a payload for one of a number of industrial control protocols.
LINKTYPE_BLUETOOTH_LE_LL 251 DLT_BLUETOOTH_LE_LL Bluetooth Low Energy air interface Link Layer packets, in the format described in section 2.1 "PACKET FORMAT" of volume 6 of the Bluetooth Specification Version 4.0 (see PDF page 2200), but without the Preamble.
LINKTYPE_WIRESHARK_UPPER_PDU 252 DLT_WIRESHARK_UPPER_PDU Upper-protocol layer PDU saves from Wireshark; the actual contents are determined by two tags, one or more of which is stored with each packet.
LINKTYPE_NETLINK 253 DLT_NETLINK Linux Netlink capture encapsulation.
LINKTYPE_BLUETOOTH_LINUX_MONITOR 254 DLT_BLUETOOTH_LINUX_MONITOR Bluetooth Linux Monitor encapsulation of traffic for the BlueZ stack.
LINKTYPE_BLUETOOTH_BREDR_BB 255 DLT_BLUETOOTH_BREDR_BB Bluetooth Basic Rate and Enhanced Data Rate baseband packets.
LINKTYPE_BLUETOOTH_LE_LL_WITH_PHDR 256 DLT_BLUETOOTH_LE_LL_WITH_PHDR Bluetooth Low Energy link-layer packets.
LINKTYPE_PROFIBUS_DL 257 DLT_PROFIBUS_DL PROFIBUS data link layer packets, as specified by IEC standard 61158-4-3, beginning with the start delimiter, ending with the end delimiter, and including all octets between them.
LINKTYPE_PKTAP 258 DLT_PKTAP Apple PKTAP capture encapsulation.
LINKTYPE_EPON 259 DLT_EPON Ethernet-over-passive-optical-network packets, starting with the last 6 octets of the modified preamble as specified by 65.1.3.2 "Transmit" in Clause 65 of Section 5 of IEEE 802.3, followed immediately by an Ethernet frame.
LINKTYPE_IPMI_HPM_2 260 DLT_IPMI_HPM_2 IPMI trace packets, as specified by Table 3-20 "Trace Data Block Format" in the PICMG HPM.2 specification. The time stamps for packets in this format must match the time stamps in the Trace Data Blocks.
LINKTYPE_ZWAVE_R1_R2 261 DLT_ZWAVE_R1_R2 Z-Wave RF profile R1 and R2 packets, as specified by ITU-T Recommendation G.9959, with some MAC layer fields moved.
LINKTYPE_ZWAVE_R3 262 DLT_ZWAVE_R3 Z-Wave RF profile R3 packets, as specified by ITU-T Recommendation G.9959, with some MAC layer fields moved.
LINKTYPE_WATTSTOPPER_DLM 263 DLT_WATTSTOPPER_DLM Formats for WattStopper Digital Lighting Management (DLM) and Legrand Nitoo Open protocol common packet structure captures.
LINKTYPE_ISO_14443 264 DLT_ISO_14443 Messages between ISO 14443 contactless smartcards (Proximity Integrated Circuit Card, PICC) and card readers (Proximity Coupling Device, PCD), with the message format specified by the PCAP format for ISO14443 specification.
LINKTYPE_RDS 265 DLT_RDS Radio data system (RDS) groups, as per IEC 62106, encapsulated in this form.
LINKTYPE_USB_DARWIN 266 DLT_USB_DARWIN USB packets, beginning with a Darwin (macOS, etc.) USB header.
LINKTYPE_OPENFLOW 267 DLT_OPENFLOW OpenFlow messages with an additional 12-octet header, as used in OpenBSD switch interface monitoring.
LINKTYPE_SDLC 268 DLT_SDLC SDLC packets, as specified by Chapter 1, "DLC Links", section "Synchronous Data Link Control (SDLC)" of Systems Network Architecture Formats, GA27-3136-20, without the flag fields, zero-bit insertion, or Frame Check Sequence field, containing SNA path information units (PIUs) as the payload.
LINKTYPE_TI_LLN_SNIFFER 269 DLT_TI_LLN_SNIFFER TI LLN sniffer frames.
LINKTYPE_LORATAP 270 DLT_LORATAP LoRaTap pseudo-header, followed by the payload, which is typically the PHYPayload from the LoRaWan specification.
LINKTYPE_VSOCK 271 DLT_VSOCK Protocol for communication between host and guest machines in VMware and KVM hypervisors.
LINKTYPE_NORDIC_BLE 272 DLT_NORDIC_BLE Messages to and from a Nordic Semiconductor nRF Sniffer for Bluetooth LE packets, beginning with a pseudo-header.
LINKTYPE_DOCSIS31_XRA31 273 DLT_DOCSIS31_XRA31 DOCSIS packets and bursts, preceded by a pseudo-header giving metadata about the packet.
LINKTYPE_ETHERNET_MPACKET 274 DLT_ETHERNET_MPACKET mPackets, as specified by IEEE 802.3br Figure 99-4, starting with the preamble and always ending with a CRC field.
LINKTYPE_DISPLAYPORT_AUX 275 DLT_DISPLAYPORT_AUX DisplayPort AUX channel monitoring data as specified by VESA DisplayPort (DP) Standard preceded by a pseudo-header.
LINKTYPE_LINUX_SLL2 276 DLT_LINUX_SLL2 Linux "cooked" capture encapsulation v2.
LINKTYPE_SERCOS_MONITOR 277 DLT_SERCOS_MONITOR Sercos Monitor.
LINKTYPE_OPENVIZSLA 278 DLT_OPENVIZSLA Openvizsla FPGA-based USB sniffer.
LINKTYPE_EBHSCR 279 DLT_EBHSCR Elektrobit High Speed Capture and Replay (EBHSCR) format.
LINKTYPE_VPP_DISPATCH 280 DLT_VPP_DISPATCH Records in traces from the http://fd.io VPP graph dispatch tracer, in the the graph dispatcher trace format.
LINKTYPE_DSA_TAG_BRCM 281 DLT_DSA_TAG_BRCM Ethernet frames, with a switch tag inserted between the source address field and the type/length field in the Ethernet header.
LINKTYPE_DSA_TAG_BRCM_PREPEND 282 DLT_DSA_TAG_BRCM_PREPEND Ethernet frames, with a switch tag inserted before the destination address in the Ethernet header.
LINKTYPE_IEEE802_15_4_TAP 283 DLT_IEEE802_15_4_TAP IEEE 802.15.4 Low-Rate Wireless Networks, with a pseudo-header containing TLVs with metadata preceding the 802.15.4 header.
LINKTYPE_DSA_TAG_DSA 284 DLT_DSA_TAG_DSA Ethernet frames, with a switch tag inserted between the source address field and the type/length field in the Ethernet header.
LINKTYPE_DSA_TAG_EDSA 285 DLT_DSA_TAG_EDSA Ethernet frames, with a programmable Ethernet type switch tag inserted between the source address field and the type/length field in the Ethernet header.
LINKTYPE_ELEE 286 DLT_ELEE Payload of lawful intercept packets using the ELEE protocol. The packet begins with the ELEE header; it does not include any transport-layer or lower-layer headers for protocols used to transport ELEE packets.
LINKTYPE_Z_WAVE_SERIAL 287 DLT_Z_WAVE_SERIAL Serial frames transmitted between a host and a Z-Wave chip over an RS-232 or USB serial connection, as described in section 5 of the Z-Wave Serial API Host Application Programming Guide.
LINKTYPE_USB_2_0 288 DLT_USB_2_0 USB 2.0, 1.1, or 1.0 packet, beginning with a PID, as described by Chapter 8 "Protocol Layer" of the the Universal Serial Bus Specification Revision 2.0. Deprecated in favor of speed specific USB 2.0, 1.1, or 1.0 linktypes.
LINKTYPE_ATSC_ALP 289 DLT_ATSC_ALP ATSC Link-Layer Protocol frames, as described in section 5 of the A/330 Link-Layer Protocol specification, found at the ATSC 3.0 standards page, beginning with a Base Header.
LINKTYPE_ETW 290 DLT_ETW Event Tracing for Windows messages, beginning with a pseudo-header.
LINKTYPE_NETANALYZER_NG 291 DLT_NETANALYZER_NG Hilscher Gesellschaft fuer Systemautomation mbH netANALYZER NG hardware and software (specification).
LINKTYPE_ZBOSS_NCP 292 DLT_ZBOSS_NCP Serial NCP (Network Co-Processor) protocol for Zigbee stack ZBOSS by DSR. ZBOSS NCP protocol, beginning with a header.
LINKTYPE_USB_2_0_LOW_SPEED 293 DLT_USB_2_0_LOW_SPEED Low-Speed USB 2.0, 1.1, or 1.0 packet, beginning with a PID, as described by Chapter 8 "Protocol Layer" of the the Universal Serial Bus Specification Revision 2.0.
LINKTYPE_USB_2_0_FULL_SPEED 294 DLT_USB_2_0_FULL_SPEED Full-Speed USB 2.0, 1.1, or 1.0 packet, beginning with a PID, as described by Chapter 8 "Protocol Layer" of the the Universal Serial Bus Specification Revision 2.0.
LINKTYPE_USB_2_0_HIGH_SPEED 295 DLT_USB_2_0_HIGH_SPEED High-Speed USB 2.0 packet, beginning with a PID, as described by Chapter 8 "Protocol Layer" of the the Universal Serial Bus Specification Revision 2.0.
LINKTYPE_AUERSWALD_LOG 296 DLT_AUERSWALD_LOG Auerswald Logger Protocol, as described in this document.