NIC going to sleep on Ubuntu Server 10.04

Bear with me. Unlike most here I'm a hard-core hardware guy (aka, an Electronics Tech) so this suggestion is going to be out of the norm, at least here. What I'm about to describe is quite common in networking gear. It's probably the most common hardware problem in networking devices outside the PC. [I've repaired enough of it personally to be able to say that..]

To explain your symptoms: There is an IC chip in your switch that is responsible to tell the rest of the network that your server is 'up'. That chip knows to do this by a voltage being applied to one of it's pins. That voltage is 'held up' by a capacitor in between server activities. The cap is initially charged due the chip's activity when the server 'sends' through the switch but the cap supposed to hold that charge for hours, not minutes.

The suggested senario is thus: You stop using the server and this cap 'leaks down' so the voltage on that IC chip's pin goes too low. The network now thinks your server is off-line. When you reinitiate server activity the cap charges up to voltage again - but it takes a little time - hence the delayed responce. - Once the cap is up to voltage everything is fine again.

By pinging every 10 seconds you are artificially keeping the leaky cap charged.

Cheap Chinese or Taiwan made capacitors in networking black-boxes (modems, routers, switches, bridges, hubs) are EXTREMELY common in ALL brands. They are in fact the norm. (Yes, even the big name brands like Cisco, Netgear, Linksys commonly use them.)

If you are handy with a soldering iron they can usually be fixed for under $5 but you need to use (or -should- use) low ESR caps like Panasonic FR, FM, FC or Chemicon KY, KZE or Nichicon HE series. Those can be ordered on-line from Mouser or Digikey. [NO, Radioshack does NOT carry low ESR caps. Nor does Fry's Electronics or most brick-mortar electronics shops.]

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In some cases it can be a cap in the NIC circuit on the motherboard doing basically the same thing but that is much less likely. When those fail they typically kill the NIC's function completely. .