I have a home server (ArchLinux) on which I run Mumble voip and Apache http. Recently some of my users have started to get issues with the voice cutting out and their client reports a high packet loss of the UDP packets coming from the server.

The server is connected to my 100/100Mbit internet through a DI-524 home router being used as a switch. To this switch a home PC and another identical switch are also connected. The second switch has a second PC and an IP-telephony modem connected to it. All computers use their own static IP-address.

What could the problem be? Where should I start looking?