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When I leave my server idle for about 10 minutes the network will stop responding to outside connections. If I get on the server and attempt to use the network(ping google for example) there will be a delay for a few seconds and then it works. After this incoming connections work again until I leave it idle again. Why does this happen and how can I fix it?

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shortly after idling and losing your connection, log into the server, and type dmesg | tail -n30 to show the last 30 lines of dmesg, and see if there are any hints or indications in there as to why your NIC is losing it's connection. if you can't find anything, try posting it on here, so we can see what's going on. –  cpbills May 18 '10 at 2:23
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4 Answers

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. .

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Are you sure that it is due to the NIC ? The switch port goes down ? Check your system logs in /var/log/kern.log, look for firewall or NIC up/down logs. Maybe it can be due to a slow DNS/DHCP ? Interesting problem !

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I have managed to keep the server online for 3 weeks with 10 sec ping on the gataway ip

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Yes, I explained that... "By pinging every 10 seconds you are artificially keeping the leaky cap charged." –  PCBONEZ Jul 17 '12 at 2:50
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This is an old one, but I didn't see the most obvious answer anywhere.

Besides the hardware issues described in the other answers, first check that the NIC itself is not set to go into power-save mode.
It could be as simple as that...

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protected by sysadmin1138 Jul 20 '11 at 0:59

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