Ethernet Frame & 802.1Q VLAN Inspector
Inspect Ethernet MAC addresses, EtherType and one VLAN tag with byte offsets, PCP/DEI/VID fields and a trunk explanation.
About this ethernet frame & 802.1q vlan inspector
Inspect Ethernet MAC addresses, EtherType and one VLAN tag with byte offsets, PCP/DEI/VID fields and a trunk explanation Performs protocol inspection, IP calculation, and network analysis client-side without sending probes or exposing network topology.
Protocol mechanics & network logic
Paste two-digit hexadecimal octets separated by spaces, colons or hyphens, then run. Load the tagged example to see the four tag bytes highlighted between source MAC and EtherType. Editing clears the old result.
Worked network diagnostic scenario
Scenario: Parse a 14-octet Ethernet II header locally.
Sample input:
Processing: Validate octets and extract MAC addresses, EtherType and header size. Tagged example: 81 00 b0 2a at offsets 12–15 gives TPID 0x8100, PCP 5, DEI 1 and VID 42; 86 dd at 16–17 means IPv6. Header 18 bytes, payload 3 bytes.
Illustrative output:
Addressing limits & protocol boundaries
UTF-8 input text, including separators, must be below 1,000,000 bytes. A header needs 14 bytes, or 18 with one 0x8100/0x88a8 tag. Only one tag is decoded; no stacked-tag, LLC/802.3 length, payload, preamble or FCS validation. Remaining bytes are counted as payload, including any supplied padding/FCS. No capture or network traffic.
Addressing calculations and subnet models in Ethernet Frame & 802.1Q VLAN Inspector follow IETF RFC definitions. Ensure subnet masks and CIDR prefixes match your network topology.
Offline network inspection boundary
Address parsing and CIDR calculations in Ethernet Frame & 802.1Q VLAN Inspector run entirely client-side without probing external IP networks or transmitting routing data.
IETF RFC specifications & IANA registries
IETF Request for Comments (RFC) standards and IANA registry references:
Ethernet Frame & 802.1Q VLAN Inspector verification · Audit standards
How to use it
- Enter, paste, or select your input data into the Ethernet Frame & 802.1Q VLAN Inspector workspace controls.
- Review parameter fields, units, or options configured for Ethernet Frame & 802.1Q VLAN Inspector.
- Click the action button or observe immediate live calculations rendered by Ethernet Frame & 802.1Q VLAN Inspector.
Frequently asked questions
What frame fields does it actually parse?+
It splits hexadecimal octets on spaces, colons or hyphens, validates two hex digits per token, and returns destination/source MAC, EtherType, known protocol, bytes, headerBytes and payloadBytes. TPID 0x8100 or 0x88a8 reads one VLAN tag with PCP, DEI and VLAN ID.
Which controls and input limits apply?+
The page has one hexadecimal-frame text area, Run locally and Load sample. A non-VLAN Ethernet II header needs at least 14 octets; a VLAN-tagged frame needs 18. It does not capture a network interface, read a PCAP, decode IP payloads or construct packets.
How does Ethernet Frame & 802.1Q VLAN Inspector protect against invalid states or mathematical limits?+
It reads an Ethernet II header and at most one 802.1Q/802.1ad VLAN tag, returning MAC addresses, one tag's TPID/PCP/DEI/VID, and the following EtherType. Stacked tags are not recursively decoded; payload bytes, FCS, IP headers, and network traffic are not inspected. Frames shorter than 14 bytes, or 18 bytes after a VLAN TPID, fail. The 4-byte tag occupies offsets 12–15: TPID (2 bytes), then TCI (2 bytes). TCI contains PCP (3 bits), DEI (1 bit) and VID (12 bits).
What result does the worked example produce?+
In the worked example, the tool exactly matched the independent 14-octet broadcast/IPv4 vector. Separate guarded contracts matched a VLAN-42 IPv6 frame and the short-frame error. These prove local parsing of those values only; they do not prove traffic example run or network delivery. A trunk carries multiple VLANs over one link. Tags identify VLAN membership; switches forward within the configured VLAN. Untagged/native VLAN handling depends on port configuration. A header alone cannot establish the actual trunk configuration.