Post #4141968

2026-07-27 15:52 UTC

I only get 4 Gbps from my 10 Gbps server, I'll never ask "why" online, because I'm 100% guaranteed to get the silly answer of "enable Jumbo Frame". 10 GbE servers worked over Internet for a decade with no jumbo frames. Actually solving it requires testing a bunch of hypervisor, guest, routing, bridge, netfilters combinations to find the PPS bottleneck (conveniently worked around by jumbo frames).

Replies (2)

@jernej__s@infosec.exchange 2026-07-27 16:48

@niconiconi@mk.absturztau.be I was genuinely surprised when I connected the AliExpress switch with two 10 GbE ports that sits next to my modem to HPE 1950 switch in my basement, and 10 Gb link worked, despite the 55 m distance over 20 years old CAT5e. There are two more 2x10Gb+4x2.5Gb switches between my workstation and the modem switch, and I still got around 920 MB/s through SMB. I did have to replace those 55m of CAT5e about half a year later, when it simply refused to connect one day (there's a much shorter run of CAT7 now – the original cable went round and round the stairwell, I put the new one through the holes that were drilled for fibre internet).

Open ##4141967
@thedarktangent@defcon.social 2026-07-27 16:33

@niconiconi@mk.absturztau.be @drwho@masto.hackers.town We use 9000 jumbo frames and don’t see much of an improvement, but we are not saturated so it’s hard to tell. Thinks like hardware TSO, RSS, Etc seem to make a small difference.

Open ##4367170