xmit hash policy used in VDX 6740

lano1106 — Sat, 13 Mar 2021 16:05:37 GMT

I have a server connected to VDX-6740 HW in a 802.3ad LAG setup with 2 Ethernet links (Not sure about the exact setup. I am a user of your products, not the admin).

I would like to have some control over the load balancing. For outgoing messages, it is pretty easy as the formula is documented (Linux kernel documentation and bonding driver source code):
hash = source MAC XOR destination MAC XOR packet type ID
hash = hash XOR source IP XOR destination IP
hash = hash XOR (hash RSHIFT 16)
hash = hash XOR (hash RSHIFT 😎
And then hash is reduced modulo slave count.

but for incoming traffic, simply changing the ephemeral TCP port value on the server-side (which is a client of some remote service) with nothing else changing, the switch is going to change over which link it is going to send me those packets.

So clearly, the switch do use some L3_L4 hash function.

Would it be possible to know what is the exact hash formula so that I can pick a port value that will make the switch xmit me the traffic on the desired link?

thank you,

topic xmit hash policy used in VDX 6740 in ExtremeSwitching (EXOS/Switch Engine)

xmit hash policy used in VDX 6740