Jumbo Frames (MTU 9000)
Jumbo frames carry up to 9000 bytes per packet, cutting overhead on storage and cluster networks.
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Encapsulation in the Path
Inner MTU
9000 − 0 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 8960
MTU & MSS Calculator
Jumbo frames
MTU9000
TCP MSS (IPv4)8960
VXLAN Inside8950
Testping -M do -s 8972 <host>
Every device on the path, including switches, must support the same MTU, or large packets vanish. Use jumbo frames on dedicated storage, Ceph or cluster networks, not on internet-facing interfaces.
A jumbo underlay is also the easy way to run VXLAN with a full 1500-byte MTU inside: set the underlay to 1550 or more.
Questions
Should I use jumbo frames?
On a dedicated storage or cluster network where every device supports them, yes. On anything that touches the internet, no.
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