TRex Skipping Latency Packet

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Mohsen Meamarian

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Apr 4, 2025, 9:21:55 AMApr 4
to TRex Traffic Generator
Hi,

I’m facing an issue where TRex doesn't recognize the latency packet, even though both packets are the same length and carry the same latency tag at the end:

ab 19 00 00 fe ff ff ff 85 69 c7 b2 43 ea 12 00

Here are the full hex dumps of both packets:


Packet A (RX in my DUT):

00 15 4d 13 2e 13 10 70 fd 30 34 50 08 00 45 01 00 80 ff ff 00 00 40 11 04 d1 0a 00 00 01 00 d6 63 d5 08 69 08 68 00 08 00 00 01 ff 00 20 00 00 00 00 00 00 00 45 00 00 80 04 d2 00 00 40 11 00 00 0a 00 00 01 0a 00 00 02 08 69 08 68 00 08 00 00 78 00 04 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 ab 19 00 00 fe ff ff ff 85 69 c7 b2 43 ea 12 00

Packet B (TX in my DUT toward Trex):

00 15 4d 13 2e 13 10 70 fd 30 34 50 08 00 45 00 00 6e 00 01 00 00 40 11 f7 2a c0 a8 01 01 c0 a8 01 02 1f 6b 56 08 00 00 00 00 01 01 00 00 00 00 00 00 00 00 00 45 00 00 80 04 d2 00 00 40 11 00 00 0a 00 00 01 0a 00 00 02 08 69 08 68 00 08 00 00 78 00 04 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 ab 19 00 00 fe ff ff ff 85 69 c7 b2 43 ea 12 00

What could cause TRex to skip the latency pkt but recognize it in case I just mirror the rx pkt in my DUT? Could it be checking checksums or byte-shift that prevent it from detecting the latency tag?

Thanks,

chris...@gmail.com

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Sep 29, 2025, 11:42:30 PMSep 29
to TRex Traffic Generator
Hi Mohsen, 

Even I am facing similar issue .Did you find any solution for the same ?

Thanks,
Chris.

Mohsen Meamarian

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Sep 30, 2025, 5:19:20 AMSep 30
to chris...@gmail.com, TRex Traffic Generator
Hi,
The problem was packet size; the packet size should be larger than a specific number. 

Best,

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