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We have 13 computers connected to Windows 2008 Server R2 Domain. There is Windows 7 64-bit Professional on all of them. The computers have same configurations and are quite fast (Intel Core i3, fast SSD, gigabit ethernet, etc..). All computers have same antivirus and firewall with same configuration, and other software is also nearly the same.

But one of the computers have very slow ping in LAN. The ping at this computer varies from 1 to 600 ms. On the other computers, ping is fast - lower than 1ms.

I will reduce the problem to two computers from our LAN. We have:

  • PC A with good ping
  • PC B with slow ping

And now one strange thing: When I ping A from B, the ping responses are slow. But when I ping B from A, responses on A are fast.

I have tried to deactivate firewall, and logon as administrator, but there is no difference..

What can cause slow ping?

Thanks in advance

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Try booting with WinPE or some other LiveBootCD, and ping again. – EliadTech Dec 9 '13 at 13:25
Are both computers plugged into the same switch? How far apart are A and B? – Richie086 Dec 9 '13 at 19:36

Replace the ethernet cable on the machine that is slow. The cable sounds like it is damaged.

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And how do you explain this? Quote: When I ping A from B, the ping responses are slow. But when I ping B from A, responses on A are fast. – Robert Dec 9 '13 at 14:38
One of the TX/RX pairs are bad would be a simple and logical explanation – Keltari Dec 9 '13 at 14:51

I'd bet that the nameserver settings are different on B. Try pinging using the IP address rather than the hostname, it should be the same speed on both PC's. Make sure that B does not use a wrong primary nameserver, it most likely causes the delay when trying to resolve.

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