What you've described sounds like one of the example scapy scripts they ship with - it is basically generating every single packet on demand and you are bound by how fast scapy can do the job (hence the CPU utilization). Try to make the script pre-generate more packets in a single go.
I used https://github.com/Civil/simple_bench/blob/main/profiles/simple.py this script in the tests and mostly https://github.com/Civil/simple_bench/blob/main/profiles/simple.py#L58 makes it much faster. As I've said, I don't think it is a t-rex limitation, just the default settings that are suboptimal. Of course there might be something that is related to a different driver (I was using mlx5 - so mellanox and nvidia connectx and bluefield cards in my tests, I don't have any broadcom NICs), but that sounds extremely unlikely to me. On Wed, 14 Oct 2026 at 16:50, Dinesh via lists.fd.io <dinesh.g= [email protected]> wrote: > Hello vladimir, > > It's 24 core machine without hyperthreading. > > LnkCap: Port #0, Speed 32GT/s, Width x16, ASPM not supported > LnkSta: Speed 32GT/s (ok), Width x16 (ok) > > model name : Intel(R) Xeon(R) Gold 5412U > stepping : 7 > microcode : 0x2b000161 > cpu MHz : 2100.000 > > memory - DDR5 4800MT > > Broadcom 400g NIC. > > Can we modify trex source to get 400 gig with single port ? > > Also i am giving 14 cores for trex, ./t-rex-64 -i -c 14 --cfg > /etc/trex_cfg.yaml > > Still when i am passing ipv6 udp traffic, cpu utilization is 100% and > i cannot push beyond 120gig. > > > On 14/10/26 18:53, Vladimir Smirnov via lists.fd.io wrote: > > What hardware have you used for T-Rex? > > About 1.5 years ago I managed to get about ~400 Mpps / ~800 Gbps on a > single 16 core machine ( > https://nog.fi/event/26/contributions/191/attachments/120/262/Generating%201%20Tbps.pdf > - slide 39, it was 128b packets), same machine could do about 600 Mpps with > 64 byte packets and you can tune the packet size to get around 600 Mpps. > > Frankly speaking, my NICs on those boxes were capable of 200G per port > only. > > On Wed, 14 Oct 2026 at 13:12, Dinesh via lists.fd.io <dinesh.g= > [email protected]> wrote: > >> Hello everyone, >> >> What is the best tool for linux to test 400 gbps throughput in vpp ? >> >> My setup is like below. >> >> Lan -> Vpp -> Router (Pumping traffic from lan host to router) >> >> I want to test both ipv4 and ipv6. I tried with dpdk-testpmd and it >> works good with ipv4, but there is no support for ipv6 i guess. >> >> I also tried with T-rex , but somehow t-rex source code is >> hard-capped at 200gbps. >> >> >> Thanks, >> Dinesh >> >> >> >> >> > > -- > Best regards, > Vladimir Smirnov. > > > > > -- Best regards, Vladimir Smirnov.
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