Why does the network periodically fall off?

Question

Domain Name System

Good day.
There is a gateway on Ubuntu server 10.04 with configured DHCP, DNS. Clients cling to it via WiFi routers and access points to access the Internet and access local resources on SAMBA.
Recently, on some machines (on some, such a problem does not occur at all), the network periodically began to fall off, and therefore access to local resources and the Internet is lost. As a rule, the network rises again after a couple of seconds, but the fact itself is rather unpleasant (remote access sessions fall off, file downloads are interrupted, etc.).
machines were checked for viruses, but nothing was found.
Client machines use both static and dynamic network settings. They do not give anything in the logs (standard messages about the unavailability of a particular resource).
No pattern associated with the use of static / dynamic settings or specific access points has been identified.
What could be the problem?

Answer 1

Gateway with clients on different subnets? when clients fall off the main gateway is available?

Answer 2

The task from the area "my tambourine did not help. drag yours!" Expand the new DNS and wrap everything on it. If it helps, then you will already be poking around in the old one.

Answer 3

Post a trace (to some accessible node on the internet) before and after the problem. In theory, it will be seen where the connection breaks, or at least the problem becomes clearer.