I just put a 2.9b16 unit in service today and I am experiencing the same issue that I have had on a couple 2.8.2x units as well. The ARP data for the end users will time out frequently. People will be surfing, and then just go offline. Looking at the ARP data, it always disappears as soon as they say they are offline.

This isn't in a wireless situation, simply an ethernet NAT router. This particular unit is dealing with about 100 users, and about 40-50 are ever using it at the same time. The other situations are about 50 users each where about 15-20 are ever on at the same time.

I could do static ARP entries, but I don't have the time and patience to handle that, so it needs to be a dynamic ARP system. Please assist if you know how to change the timeout or know anything about this issue.

Please upgrade to v2.9beta18 and if that doesn't help, could you make the support output file when the problem arise and send it to support@mikrotik.com

I just updated the software to 2.9b18 and I am waiting to see how it goes.

Problem was related to the Tut Systems' Expresso MDU system, not the Mikrotik. For future reference, when configuring ports on any Expresso MDU from Tut, make sure that Block Downstream Broadcast is set to No. While it works set to Yes on Cisco routers, MT does not work well with it.