VXLAN MTU Calculator
VXLAN adds about 50 bytes to every packet, so over a normal 1500-byte link the inner MTU is 1450.
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Encapsulation in the Path
Inner MTU
1500 − 50 bytes of headers
TCP MSS (IPv4)
TCP MSS (IPv6)
Largest Ping (IPv4)
Clamp MSS (nftables)
nft add rule inet filter forward tcp flags syn tcp option maxseg size set 1410
MTU & MSS Calculator
VXLAN on a 1500-byte link
Overhead50 bytes
Inner MTU1450
TCP MSS (IPv4)1410
TCP MSS (IPv6)1390
Over PPPoE (1492)1442
Testping -M do -s 1422 <host>
If the inner interface keeps an MTU of 1500, packets larger than 1450 bytes are fragmented or dropped. The usual symptom: ping and small requests work, large downloads and TLS handshakes hang.
Set the VXLAN interface's MTU to 1450, or clamp TCP MSS to 1410 on the router.
MTU by Tunnel
Questions
What MTU should I use for VXLAN?
1450 over a standard 1500-byte link; 1442 over PPPoE.
How much overhead does VXLAN add?
About 50 bytes per packet.
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