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Our hosted servers are experiencing periods of very slow network access. During these periods pinging from any of our servers to the default gateway results in ping times of up to 500ms (instead of the normal 2-3ms). There are no packets lost.

The ISP is claiming their network is OK and the problem must be with the hosting service. The hosting service guys claim they have nothing at level 3 and everything according to them is OK.

I'm think our servers are connected to a switch which is connected the default gateway over a shared ATM line. Traceroute doesn't show any routers on the path.

Before changing my service providers, is there anything I could check that might explain what is causing this issue?

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I'm confused about your claim that "pinging from any of our servers to the default gateway results in ping times of up to 500ms". Are you talking about your LAN servers to your own gateway?, or the hosted servers to their own gateway? – l0c0b0x Jun 8 '09 at 6:14
    
my hosted servers to their gateway. Their gateway is not on the same lan, but ping should be less than 4ms – DanJ Jun 11 '09 at 22:32
up vote 2 down vote accepted

Routers don't prioritize handling ICMP to themselves. Pinging a router and getting high latency means nothing (well, not what you want anyway). What happens if you ping a unix system one router-hop away? Or since we are dealing with 500ms if that is the latency then that will show up clearly if you ping anyone on you continent.

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You might also want to try mtr (mtr-tiny is a nice package I have on every server).

It will give you details about all the hops that are between you and the target. Give it a try.

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PingPlotter will give you graphs of traceroute data over time so you can see exactly where and at what time you are getting problems.

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Normally, I'd avoid pinging the default gateway to measure delay. Answering ICMP is about the least-prioritised task that routers do, so all that 500 ms delay means is that the router's busy (may not even be busy routing packets, if lots of people are pinging it, because they think that's a good way of gauging the network).

If at all possible, find a host on the other side of the default gateway and ping that. It gives you a much better idea if there's anything wrong.

One of the reasons that sort of thing (answering ICMP EHO requests and other non-essential traffic handling) is de-prioritised is to make it harder to cause a denial of service, simply by smurfing the router.

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You could try arping as an alternative to the oft prioritised ICMP echo.

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protected by Sven Feb 13 at 10:25

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