As already stated.
Which is something you want for guest network. You want to limit speed to limit guests in most cases. At least that is the option available in reForis and that is what I was addressing but with a twist that there was eth1 (thus LAN).
If you are using SQM for traffic fitting and balancing then of course you most likely want it on WAN interface (eth2).
In any case, you do not want it on eth0 nor eth1 especially with DSA. This either would do nothing or cause promiscuous mode (thus switching would be disabled and all would be passed through CPU and thus bottleneck would be created). I am not sure which one would be the case but either way, it is not a good idea. That is why I wrote that having it on eth1 is potentially harmful.