Network Configuration
Minimum: 68, Maximum: 65535
IPv4 + TCP
20 + 20 bytes
IPv4 + UDP
20 + 8 bytes
IPv6 + TCP
40 + 20 bytes
IPv6 + UDP
40 + 8 bytes
IPv4 routers may fragment in transit (unless DF is set).
GRE: outer IPv4 20 B + GRE 4 B. ESP: outer IP + header, IV, trailer and ICV — roughly 52–73 B depending on cipher; 58 B (AES-CBC/SHA-1) is used here.
Size of data to transmit (IP limits total packet length to 65,535 B)
With DF set, oversized IPv4 packets are dropped and an ICMP "Fragmentation Needed" is returned.
How IP Fragmentation Works:
• The IP header is repeated in each fragment
• The transport header (TCP/UDP) travels inside the first fragment's data
• Fragment offsets are measured in 8-byte units of the IP payload
• Every fragment except the last must carry a multiple of 8 bytes
• IPv6: only the sender fragments, adding an 8-byte Fragment header per fragment
• The IP header is repeated in each fragment
• The transport header (TCP/UDP) travels inside the first fragment's data
• Fragment offsets are measured in 8-byte units of the IP payload
• Every fragment except the last must carry a multiple of 8 bytes
• IPv6: only the sender fragments, adding an 8-byte Fragment header per fragment
Fragmentation Analysis
Effective MTU
-
Total Fragments
-
Max Unfragmented Payload
-
Bytes Transmitted (L3)
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Header Overhead
-
Efficiency
-
Fragment Composition
Common MTU Sizes Reference
Ethernet
1500 bytes
PPPoE DSL
1492 bytes
IPSec VPN Tunnel
1400 bytes
IPv6 Minimum (RFC 8200)
1280 bytes
WiFi 802.11
2304 bytes
Jumbo Frames
9000 bytes