On Tue, 27 Oct 2020 19:25:16 +0100 Tobias Waldekranz <tob...@waldekranz.com> wrote:
> .-----. TO_CPU, FORWARD .-----. TO_CPU, FORWARD .-----. > | +-----------------+ +-----------------+ | > | CPU | | sw0 | | sw1 | > | +-----------------+ +-----------------+ | > '-----' FORWARD '-+-+-' FORWARD '-+-+-' > | | | | > swp1 swp2 swp3 swp4 > > So the links selected as the CPU ports will see a marginally higher load > due to all TO_CPU being sent over it. But the hashing is not that great > on this hardware anyway (DA/SA only) so some imbalance is unavoidable. The hashing is horrible :( On Turris Omnia we have 5 user ports and 2 CPU ports, and I suspect that for most of our users there is at most one peer MAC address on the other side of an user port. So if such a user has 5 devices connected to each switch port, there are 5 pairs of (DA,SA), so 2^5 = 32 different assignments of (DA,SA) pairs to CPU ports. With probability 2/32 = 6.25% traffic from all 5 user ports would go via one port, with probability 10/32 = 31.25% traffic from 4 user ports would go via one port. That is not good balancing :) Marek
